Publications by authors named "Kotaro Iijima"

64 Publications

Neutron flux evaluation model provided in the accelerator-based boron neutron capture therapy system employing a solid-state lithium target.

Sci Rep 2021 Apr 13;11(1):8090. Epub 2021 Apr 13.

Division of Research and Development for Boron Neutron Capture Therapy, National Cancer Center Exploratory Oncology Research & Clinical Trial Center, Tsukiji 5-1-1, Chuo-ku, Tokyo, 104-0045, Japan.

An accelerator-based boron neutron capture therapy (BNCT) system employing a solid-state Li target can achieve sufficient neutron flux for treatment although the neutron flux is reduced over the lifetime of its target. In this study, the reduction was examined in the five targets, and a model was then established to represent the neutron flux. In each target, a reduction in neutron flux was observed based on the integrated proton charge on the target, and its reduction reached 28% after the integrated proton charge of 2.52 × 10 mC was delivered to the target in the system. The calculated neutron flux acquired by the model was compared to the measured neutron flux based on an integrated proton charge, and the mean discrepancies were less than 0.1% in all the targets investigated. These discrepancies were comparable among the five targets examined. Thus, the reduction of the neutron flux can be represented by the model. Additionally, by adequately revising the model, it may be applicable to other BNCT systems employing a Li target, thus furthering research in this direction. Therefore, the established model will play an important role in the accelerator-based BNCT system with a solid-state Li target in controlling neutron delivery and understanding the neutron output characteristics.
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http://dx.doi.org/10.1038/s41598-021-87627-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8044165PMC
April 2021

A dosimetric and centeredness comparison of the conventional and novel endobronchial applicators: A preliminary study.

Brachytherapy 2021 Mar-Apr;20(2):467-477. Epub 2021 Jan 19.

Department of Radiation Oncology, National Cancer Center Hospital, Chuo City, Tokyo, Japan.

Purpose: This study compared the applicator position relative to the tracheal wall and dosimetric parameters between conventional and novel applicators among patients receiving endobronchial brachytherapy (EBBT) for intratracheal tumors.

Methods And Materials: Data from 7 patients who received EBBT for intratracheal tumors were retrospectively analyzed; 4 and 3 patients were treated with conventional (2-wing) or novel (5-wing) applicators, respectively. Applicator centrality was evaluated using the distance between the center of the trachea and main bronchus (TMB) lumen and path of source (L). Dosimetric parameters, including plans normalized to D of the TMB = 45 Gy (normalized plan), were compared between the applicators.

Results: The mean and maximum values of L in cases of the 2-wing applicator group were approximately 5.0 mm and 10.0 mm, respectively. In the novel applicator group, the corresponding values were approximately 3.0 and 6.0 mm, respectively. In the normalized plan of the 2-wing applicator group, the ranges of median V of clinical target volume (CTV) and D of the TMB in all cases were 23.0-91.9% and 66.3-153.1 Gy, respectively. In the 5-wing applicator group, the corresponding values were 69.2-83.8% and 60.4-84.5 Gy, respectively.

Conclusions: In the 5-wing applicator group, the range was narrow in all dose-volume parameters except for D of the TMB. Compared to the conventional applicator, the 5-wing applicator can give a stable dose to the CTV and can reduce the maximum dose of the TMB. This suggests that stable EBBT can be given to any patient using the 5-wing applicator.
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http://dx.doi.org/10.1016/j.brachy.2020.11.005DOI Listing
January 2021

Dosimetric effect of the intestinal gas of online adaptive stereotactic body radiotherapy on target and critical organs without online electron density correction for pancreatic cancer.

Br J Radiol 2021 Mar 5;94(1119):20200239. Epub 2021 Feb 5.

Department of Radiation Oncology, National Cancer Center Hospital, Tokyo, Japan.

Objective: This study aimed to assess the dosimetric effect of intestinal gas of stereotactic magnetic resonance (MR)-guided adaptive radiation therapy (SMART) on target and critical organs for pancreatic cancer without online electron density correction (EDC).

Methods: Thirty pancreatic cancer patients who underwent online SMART were selected for this study. The treatment time of each stage and the total treatment time were recorded and analyzed. The concerned dose-volume parameters of target and organs-at-risk (OAR) were compared with and without an intestinal gas EDC using the Wilcoxon-signed rank test. Analysis items with value < 0.05 were considered statistically significant. The relationships between dosimetric differences and intestinal gas volume variations were investigated using the Spearman test.

Results: The average treatment time was 82 min, and the average EDC time was 8 min, which accounted for 10% of the overall treatment time. There were no significant differences in CTV (GTV), PTV, bowel, stomach, duodenum, and skin ( > 0.05) with respect to dose volume parameters. For the of gastrointestinal organs ( = 0.03), the mean dose of the liver ( = 0.002) and kidneys ( = 0.03 and = 0.04 for the left and right kidneys, respectively), there may be a risk of slight overestimation compared with EDC, and for the of the spinal cord ( = 0.02), there may be a risk of slight underestimation compared with EDC. A weak correlation for in the PTV and in the duodenum was observed.

Conclusion: For patients with similar inter-fractional intestinal gas distribution, EDC had little dosimetric effects on the of all GI organs and dose volume parameters of target in most plans.

Advances In Knowledge: By omitting the EDC of intestinal gas, the online SMART treatment time can be shortened.
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http://dx.doi.org/10.1259/bjr.20200239DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8011255PMC
March 2021

The use of hyperbaric oxygen to treat actinic rectal fistula after SpaceOAR use and radiotherapy for prostate cancer: a case report.

BMC Urol 2020 Dec 14;20(1):196. Epub 2020 Dec 14.

Department of Radiation Therapy, National Cancer Center Hospital, Tsukiji 5-1-1, Chuo-ku, Tokyo, Japan.

Background: In definitive radiation therapy for prostate cancer, the SpaceOAR® System, a hydrogel spacer, is widely used to decrease the irradiated dose and toxicity of rectum. On the other hand, periprostatic abscesses formation and rectal perforation are known as rare adverse effects of SpaceOAR. Nevertheless, there is a lack of reports clarifying the association between aggravation of abscesses and radiation therapy, and hyperbaric oxygen therapy (HBOT) is effective for a peri-SpaceOAR abscess and rectal perforation.

Case Presentation: We report a case of a 78-year-old high-risk prostate cancer patient. After SpaceOAR insertion into the correct space, he started to receive external beam radiation therapy (EBRT). He developed a fever, perineal pain and frequent urination after the completion of EBRT, and the magnetic resonance imaging (MRI) revealed a peri-SpaceOAR abscess. Scheduled brachytherapy was postponed, administration of antibiotics and opioid via intravenous drip was commenced, and transperineal drainage was performed. After the alleviation of the abscess, additional EBRT instead of brachytherapy was performed with MRI-guided radiation therapy (MRgRT). On the last day of the MRgRT, perineal pain reoccurred, and MRI and colonoscopy detected the rectal perforation. He received an intravenous antibiotics drip and HBOT, and fully recovered from the rectal perforation.

Conclusions: Our report indicates that EBRT can lead to a severe rectum complication by causing inflammation for patients with a peri-SpaceOAR abscess. Furthermore, HBOT was effective for the peri-SpaceOAR abscess and rectal perforation associated with EBRT.
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http://dx.doi.org/10.1186/s12894-020-00767-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7737272PMC
December 2020

Clinicopathological features of breast cancer without mammographic findings suggesting malignancy.

Breast 2020 Dec 26;54:335-342. Epub 2020 Nov 26.

Department of Breast Oncology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.

Background: Mammography (MG) is widely used for screening examinations. Dense breast reduces MG screening sensitivity, possibly delaying diagnosis. However, little is known about the characteristics of breast cancers without MG findings indicative of malignancy. Hence, we investigated breast cancer patients with tumors not detected by MG.

Patients And Methods: In total, 1758 Japanese patients with breast cancer, undergoing curative surgery between 2012 and 2018 without neo-adjuvant chemotherapy, were retrospectively investigated. Clinicopathological features were compared between patients without (MG-negative) and with (MG-positive) cancer-specific findings on MG. The current study included cases who came to our hospital after experiencing subjective symptoms, or whose tumors were detected by MG and/or US-screening. We reviewed results of both MG and US conducted at our institution.

Results: There were 201 MG-negative cases (11.4%). In patients with invasive disease, multivariate analysis revealed MG-negative patients to have higher breast density on MG (p < 0.001). Tumors of MG-negative patients were smaller (p < 0.001), showed less lymph node involvement (p = 0.011), and were of lower grade (p = 0.027). The majority of MG-negative tumors were found by ultrasound screening, being smaller than tumors in patients with subjective symptoms. In the MG-negative group, tumor characteristics such as tumor grade did not differ between those detected by screening versus subjective symptoms.

Conclusion: Most tumors in MG-negative group patients were identified by US screening and the diseases were found at early stages with low malignancy. The usefulness of additional ultrasound with MG-screening might merit further investigations.
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http://dx.doi.org/10.1016/j.breast.2020.11.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7721633PMC
December 2020

Difficulty Diagnosing a Brain Tumor during Clinical Maintenance of a Complete Response to anti-HER2 Treatments for Metastatic Breast Cancer: A Case Report.

Case Rep Oncol 2020 Sep-Dec;13(3):1311-1316. Epub 2020 Oct 23.

Department of Breast Oncology, Juntendo University School of Medicine, Tokyo, Japan.

A 46-year-old woman with erythema of the right breast presented to our hospital and was diagnosed with stage IV breast cancer (HER2-positive invasive ductal carcinoma). She received 4 courses of anthracycline-based regimens and 4 courses of trastuzumab + pertuzumab + docetaxel (Tmab + Pmab + DTX). Since she responded well to these therapies, only Tmab + Pmab was continued thereafter. Twenty-three months after starting treatment, she developed a headache. A tumor was identified in the right temporal lobe. Craniotomy was performed for definitive diagnosis. Intraoperative pathological assessment suggested the tumor to be brain metastasis of breast cancer. However, the final pathological diagnosis was diffuse large B-cell lymphoma of central nervous system (DLBCL-CNS) based on re-assessment with immunohistochemical examinations. Therefore, the Tmab + Pmab was discontinued, and 6 courses of high-dose methotrexate therapy were administered. This case highlights the importance of considering rare entities, such as DLBCL, when diagnosing a solitary brain tumor in a patient with a primary cancer, based on imaging and pathological findings.
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http://dx.doi.org/10.1159/000511051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7670346PMC
October 2020

Configuration analysis of the injection position and shape of the gel spacer in gynecologic brachytherapy.

Brachytherapy 2021 Jan-Feb;20(1):95-103. Epub 2020 Oct 1.

Department of Radiation Oncology, National Cancer Center Hospital, Tokyo, Japan.

Purpose: In this single-institution retrospective study, configuration analysis was performed to determine the optimal location and volume of hyaluronic acid gel spacer injection into the rectovaginal or vesicovaginal septum for effective dose reduction (DR) to the organs at risk (OARs), the rectum and bladder.

Methods And Materials: 70 and 50 intracavitary brachytherapy treatment plans used only vaginal cylinders with gel spacers for the rectal and bladder sides, respectively, whereas 28 did not use spacers. Correlation analysis was performed between the geometrical parameters and injection position of the gel spacers and the 2-cm covering doses of the OARs for each treatment.

Results: A higher DR was predicted for hyaluronic acid gel spacer injection within ±5 mm and ±2.5 mm in the lateral-medial direction from the midpoint on the rectal and bladder sides, and ±10 mm in the cranial-caudal direction from the midpoint on the rectal side. There were correlations between 2-cm covering doses and the gel spacer parameters: the volume on the rectal (p = 0.02) and bladder (p = 0.04) sides; the craniocaudal length on the rectal side (p << 0.05); and ventrodorsad thickness on each OAR (p << 0.05) sides. There was no significant difference in the DR between a volume of ∼10 cm and that of a higher volume (p >> 0.05).

Conclusions: A gel spacer volume of ∼10 cm provides sufficient OAR DR if its gravity point is on the midpoint between the cylinder applicator and OAR, and its craniocaudal length covers the active length of the cylinder applicator.
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http://dx.doi.org/10.1016/j.brachy.2020.08.021DOI Listing
October 2020

Breast cancer survival among Japanese individuals and US residents of Japanese and other origins: a comparative registry-based study.

Breast Cancer Res Treat 2020 Nov 20;184(2):585-596. Epub 2020 Aug 20.

Department of Surgery, Teikyo University School of Medicine, Tokyo, Japan.

Background: Breast cancer survival outcomes vary across different ethnic groups. We clarified the differences in clinicopathological and survival characteristics of breast cancer among Japanese, US residents with Japanese origin (USJ), and US residents with other origins (USO).

Method: Using Surveillance, Epidemiology, and End Results (SEER) 18 dataset and Japanese Breast Cancer Society (JBCS) registry, we included patients first diagnosed with breast cancer between 2004 and 2015. We categorized the patients into three groups based on the database and the recorded ethnicity: Japanese (all those from the JBCS registry), USJ (those from SEER with ethnicity: Japanese), and USO (those from SEER with ethnicity other than Japanese). Excluding patients diagnosed after 2012, stage 0, and 4 patients, we examined the overall survival (OS) and breast cancer-specific survival (BCSS) using the Kaplan-Meier method and Cox proportional hazards models, adjusting for age, sex, cancer stage, and hormone receptor (HR) status.

Results: We identified 7362 USJ, 701,751 USO, and 503,013 Japanese breast cancer patients. The proportion of HR-positive breast cancer was the highest among USJ (71%). OS was significantly longer among Japanese and USJ than USO (Hazard ratio 0.46; 95% Confidence Interval [CI] 0.45-0.47 for Japanese and 0.66 [95% CI 0.59-0.74] for USJ) after adjusting for baseline covariates. BCSS was also significantly higher in the two groups (HR 0.53 [95% CI 0.51-0.55] for Japanese and 0.53 [95% CI 0.52-0.74] for USJ).

Conclusions: In stage I-III breast cancer, Japanese and US residents with Japanese origin experienced significantly longer survival than US residents with non-Japanese origins.
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http://dx.doi.org/10.1007/s10549-020-05869-yDOI Listing
November 2020

Predictive Factors for Non-sentinel Nodal Metastasis in Patients With Sentinel Lymph Node-positive Breast Cancer.

Anticancer Res 2020 Aug;40(8):4405-4412

Department of Breast Oncology, Juntendo University School of Medicine, Tokyo, Japan.

Background: Axillary dissection is routinely conducted for all patients with sentinel node (SN)-positive breast cancer. Metastasis to non SNs is not often found after axillary dissection in patients with SN-positive breast cancer. Thus, we investigated clinicopathological features, including immune cells in peripheral blood, in order to identify factors related to metastasis to non-SNs.

Patients And Methods: We retrospectively investigated 184 patients with SN-positive disease, treated at our institution during the 2013 through 2018 period. All clinicopathological data were obtained before and during surgery.

Results: Metastasis to non SNs was observed in 64 cases (35%). The platelet-to-lymphocyte ratio (PLR) and the number of SN metastases were independent of metastasis to non SNs (p=0.023 and p=0.017, respectively). Patients with metastasis to non SNs had significantly lower PLR and more SN metastases. High lymphocyte number and low platelet number resulted in a low PLR.

Conclusion: PLR might be a marker of metastasis to non SNs.
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http://dx.doi.org/10.21873/anticanres.14445DOI Listing
August 2020

Annual report of the Japanese Breast Cancer Registry for 2017.

Breast Cancer 2020 Sep 24;27(5):803-809. Epub 2020 Jul 24.

Department of Breast Surgery, Kyorin University Hospital, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan.

Background: The Japanese Breast Cancer Society Registry started in 1975; it was transferred to the registry platform of the National Clinical Database in 2012. We provide the annual data and an analysis of the Breast Cancer Registry for 2017.

Methods: Patients' characteristics and pathological data of the 95,203 registered Japanese breast cancer patients from 1,427 institutes in 2017 were obtained. Trends in age at diagnosis and pathological stage were determined during the most recent 6 years (2012-2017).

Results: The mean onset age was 60.2 years with bimodal peaks at 45-49 years and 65-69 years. A short-term trend of the most recent 6 years of data caused the second, older peak. At diagnosis, 32.4% of breast cancer patients were premenopausal. The distribution of stages revealed that the proportion of early stage breast cancer (stage 0-I) increased up to 60%. At the initial diagnosis, 2.2% of patients presented with metastatic disease. Sentinel node biopsy without axillary node dissection was performed without neoadjuvant chemotherapy (NAC) in 68.8%, and with NAC in 31.1%, of patients. For patients without NAC, lymph node metastasis was less than 3% if the tumor size was less than 1 cm. The proportion of node-negativity decreased to 79.5% when tumor size was 2.1-5 cm.

Conclusions: This analysis of the registry provides new information for effective treatment in clinical practice, cancer prevention, and the conduct of clinical trials. Further development of the registry and progress in collecting prognostic data will greatly enhance its scientific value.
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http://dx.doi.org/10.1007/s12282-020-01139-3DOI Listing
September 2020

A case report of a patient with bulky uterine cervical neoplasm who achieved complete response with "intentional internal high-dose policy" high-dose-rate interstitial brachytherapy.

Medicine (Baltimore) 2020 Jul;99(27):e20860

Department of Radiation Therapy, National Cancer Center Hospital, Tokyo.

Rationale: Gynecological high-dose-rate (HDR) brachytherapy has progressed for years, but it remains difficult for bulky tumors to be controlled locally. Dose limitations to organs at risk (OARs) are invariably obstacles in increasing the prescription dose. Additionally, it is controversial that the excessive hyperdose sleeve, the volume receiving a dose equal to or greater than twice the reference dose, should be eliminated in gynecological HDR brachytherapy. On the other hand, the technique of simultaneous integrated protection was reported for large hepatocellular carcinoma treatment, and similarly, internal high-dose brachytherapy could be used for treating bulky cervical carcinoma.

Patient Concerns: A 54-year-old female had irregular genital bleeding and lost 13 kg in one year.

Diagnosis: She was diagnosed with T3bN1M0 cervical cancer in another hospital. The transverse diameter of the primary tumor was 10.5 cm.

Interventions: The whole pelvis and para-aortic lymph node were irradiated with a total of 50 Gy in 25 fractions, but the size of the tumor showed only a slight decrease to 8.9 cm. After external beam radiotherapy, first-time high-dose-rate interstitial brachytherapy (HDR-ISBT) was administered without "intentional internal high-dose (IIHD) policy," the technique of high-dose administration to only the inside of the tumor. Considering the rectum dose limitation, in the additional 2 times of brachytherapy, "IIHD policy" HDR-ISBT was applied. In the second and third HDR-ISBT, the percentage of the volume exposed to 200% of the prescribed dose for high-risk clinical target volume increased by 241% and 204% compared with the first HDR-ISBT, while the doses to OARs were not significantly higher than those of the first-time HDR-ISBT.

Outcomes: Complete response was obtained, and no recurrence findings and side effects caused by HDR-ISBT have been detected for 2 years and 9 months.

Lessons: To our knowledge, this is the first report of IIHD HDR-ISBT for bulky cervical cancer. This technique can be the solution for treating bulky cervical cancer.
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http://dx.doi.org/10.1097/MD.0000000000020860DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7337609PMC
July 2020

Annual report of the Japanese Breast Cancer Society registry for 2016.

Breast Cancer 2020 Jul 11;27(4):511-518. Epub 2020 May 11.

Department of Surgery, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8606, Japan.

The Japanese Breast Cancer Society (JBCS) registry began data collection in 1975, and it was integrated into National Clinical Database in 2012. As of 2016, the JBCS registry contains records of 656,896 breast cancer patients from more than 1400 hospitals throughout Japan. In the 2016 registration, the number of institutes involved was 1422, and the total number of patients was 95,870. We herein present the summary of the annual data of the JBCS registry collected in 2016. We analyzed the demographic and clinicopathologic characteristics of registered breast cancer patients from various angles. Especially, we examined the registrations on family history, menstruation, onset age, body mass index according to age, nodal status based on tumor size and subtype, and proportion based on ER, PgR, and HER2 status. This report based on the JBCS registry would support clinical management for breast cancer patients and clinical study in the near future.
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http://dx.doi.org/10.1007/s12282-020-01081-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297705PMC
July 2020

[Summary of the Report of Task Group 100 of the AAPM: Application of Risk Analysis Methods to Radiation Therapy Quality Management].

Igaku Butsuri 2020 ;40(1):28-34

Department of Radiation Oncology, National Cancer Center Hospital.

In 2016, the American Association of Physicists in Medicine (AAPM) has published a report of task group (TG) 100 with a completely new concept, entitled "application of risk analysis methods to radiation therapy quality management." TG-100 proposed implementation of risk analysis in radiotherapy to prevent harmful radiotherapy accidents. In addition, it enables us to conduct efficient and effective quality management in not only advanced radiotherapy such as intensity-modulated radiotherapy and image-guided radiotherapy but also new technology in radiotherapy. It should be noted that treatment process in modern radiotherapy is absolutely more complex and it needs skillful staff and adequate resources. TG-100 methodology could identify weakness in radiotherapy procedure through assessment of failure modes that could occur in overall treatment processes. All staff in radiotherapy have to explore quality management in radiotherapy safety.
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http://dx.doi.org/10.11323/jjmp.40.1_28DOI Listing
September 2020

Neutrophil-to-lymphocyte ratio and histological type might predict clinical responses to eriburin-based treatment in patients with metastatic breast cancer.

Breast Cancer 2020 Jul 27;27(4):732-738. Epub 2020 Feb 27.

Department of Breast Oncology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.

Background: Metastatic breast cancer (MBC) is generally considered to be incurable. Although many options are available for treating MBC, physicians often encounter difficulties in choosing the most appropriate treatment because the MBCs of individual patients respond differently even to the same treatments. Thus, predictive markers for therapeutic efficacy are urgently needed. Neutrophil- and platelet-to-lymphocyte ratios (NLR and PLR, respectively), have been studied and established as prognostic markers for breast cancer patients but whether either or both of these markers are predictive of treatment responses is still unclear. Herein, we investigated predictive markers for eribulin-based treatment responsiveness in patients with MBC, by examining clinicopathological features, including several markers of immunocompetent cells in peripheral blood.

Methods: Clinicopathological features of the 104 patients with metastatic/Stage IV breast cancer given eribulin-based regimens were investigated in relation to clinical responses to eribulin-based treatments and progression-free-survival (PFS).

Results: Special histological types and high NLR at baseline were independently related to poor clinical responses to the treatments (p = 0.023 and 0.039, respectively). The Cox hazard model revealed that patients with oestrogen receptor (ER)-negative tumours and high NLR, monocyte-to-lymphocyte ratio (MLR) and PLR showed significantly shorter PFS (p = 0.021, 0.005, 0.008 and 0.030, respectively). On multivariate analysis, only ER status and NLR remained independent factors related to PFS (p = 0.011 and 0.003, respectively).

Conclusions: Our data revealed that special histological types and high NLR might be factors related to low responsiveness to eribulin-based regimens in patients with MBC.
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http://dx.doi.org/10.1007/s12282-020-01069-0DOI Listing
July 2020

Characterization of the relationship between neutron production and thermal load on a target material in an accelerator-based boron neutron capture therapy system employing a solid-state Li target.

PLoS One 2019 22;14(11):e0225587. Epub 2019 Nov 22.

Department of Medical Physics, National Cancer Center Hospital, Chuo-ku, Tokyo, Japan.

An accelerator-based boron neutron capture therapy (BNCT) system that employs a solid-state Li target can achieve sufficient neutron flux derived from the 7Li(p,n) reaction. However, neutron production is complicated by the large thermal load expected on the target. The relationship between neutron production and thermal load was examined under various conditions. A target structure for neutron production consists of a Li target and a target basement. Four proton beam profiles were examined to vary the local thermal load on the target structure while maintaining a constant total thermal load. The efficiency of neutron production was evaluated with respect to the total number of protons delivered to the target structure. The target structure was also evaluated by observing its surface after certain numbers of protons were delivered. The yield of the sputtering effect was calculated via a Monte Carlo simulation to investigate whether it caused complications in neutron production. The efficiency of neutron production and the amount of damage done depended on the proton profile. A more focused proton profile resulted in greater damage. The efficiency decreased as the total number of protons delivered to the target structure increased, and the rate of decrease depended on the proton profile. The sputtering effect was not sufficiently large to be a main factor in the reduction in neutron production. The proton beam profile on the target structure was found to be important to the stable operation of the system with a solid-state Li target. The main factor in the rate of reduction in neutron production was found to be the local thermal load induced by proton irradiation of the target.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0225587PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874357PMC
March 2020

Inter-fractional variations in the dosimetric parameters of accelerated partial breast irradiation using a strut-adjusted volume implant.

J Radiat Res 2020 Jan;61(1):123-133

Department of Medical Physics, National Cancer Center Hospital, Chuo-ku, Tsukiji 5-1-1, Tokyo, 104-0045, Japan.

The aim of the study was to evaluate inter-fractional dosimetric variations for high-dose rate breast brachytherapy using a strut-adjusted volume implant (SAVI). For the nine patients included, dosimetric constraints for treatment were as follows: for the planning target volume for evaluation (PTV_Eval), the volume receiving 90, 150 and 200% of the prescribed dose (V90%,150%,200%) should be >90%, ≤50 cm3 and ≤20 cm3, respectively; the dose covering 1 cm3 (D1cc) of the organs at risk should be ≤110% of the prescribed dose; and the air volume should be ≤10% of PTV_Eval. Differences in V90%,150%,200%, D1cc and air volume ($\Delta V$ and $\Delta D$) as inter-fractional dosimetric variations and SAVI displacements were measured with pretreatment and planning computed tomography (CT) images. Inter-fractional dosimetric variations were analyzed for correlations with the SAVI displacements. The patients were divided into two groups based on the distance of the SAVI from the surface skin to assess the relationship between the insertion position of the SAVI and dosimetric parameters. The median ΔV90%,150%,200% for the PTV_Eval in all patients was -0.3%, 0.2 cm3 and 0.2 cm3, respectively. The median (range) ΔD1cc for the chest wall and surface skin was -0.8% (-18.9 to 9.4%) and 0.3% (-7.6 to 5.3%), respectively. SAVI displacement did not correlate with inter-fractional dosimetric variations. In conclusion, the dose constraints were satisfied in most cases. However, there were inter-fractional dosimetric changes due to SAVI displacement.
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http://dx.doi.org/10.1093/jrr/rrz061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7022137PMC
January 2020

Impact of circulating tumour cells on survival of eribulin-treated patients with metastatic breast cancer.

Med Oncol 2019 Sep 13;36(10):89. Epub 2019 Sep 13.

Department of Breast Oncology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.

Several clinical studies have examined circulating tumour cells (CTCs). However, the application of CTCs as a predictive/prognostic marker for breast cancer patients has yet to be established, particularly the selection of suitable markers for detecting CTCs. We recently investigated CTCs, including mesenchymal status, from metastatic breast cancer patients who had received eribulin-based treatment. We found that assessment of both mesenchymal and epithelial CTCs might be important for predicting eribulin responsiveness. In the current study, we followed up the outcomes of these patients after eribulin treatment and investigated the possibility of CTC analysis results serving as prognostic markers for this patient population. Twenty-one patients were enrolled and peripheral blood samples were collected before eribulin-based treatments. CTCs were then examined using a Microfluidic Chip device. CTCs positive for vimentin and pan-cytokeratin were defined as mesenchymal and epithelial CTCs, respectively. Overall survival (OS) was assessed in relation to the number of CTCs and clinicopathological factors. During the observation period, 13 patients (62%) died due to breast cancer and the median OS was 18 months. Patients with high-grade tumours and a high total number of CTCs showed significantly shorter OS than those with low-grade tumours and smaller CTC burdens (p = 0.026 and 0.037, respectively). Patients who received eribulin as the first chemotherapy for metastatic disease showed longer OS (p = 0.006). Our data suggest that determining numbers of both mesenchymal and epithelial CTCs might predict survival for patients receiving eribulin.
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http://dx.doi.org/10.1007/s12032-019-1314-9DOI Listing
September 2019

A population-based recurrence risk management study of patients with pT1 node-negative HER2+ breast cancer: a National Clinical Database study.

Breast Cancer Res Treat 2019 Dec 26;178(3):647-656. Epub 2019 Aug 26.

Department of Surgery, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8606, Japan.

Purpose: Recurrence risk management of patients with small (≤ 2 cm), node-negative, human epidermal growth factor receptor 2 (HER2)-positive breast cancer remains challenging. We studied the effects of adjuvant chemotherapy and/or trastuzumab and survival outcomes among these patients, using data from the population-based Japanese National Clinical Database (NCD).

Methods: We identified a cohort of 2736 breast cancer patients with HER2+ pT1N0 disease: 489 pT1a, 642 pT1b, and 1623 pT1c. The median observation period was 76 months, and the 5-year follow-up rate was 48.2%. The number of events was 212 for disease-free survival (DFS), 40 for breast cancer-specific survival, and 84 for overall survival (OS).

Results: There were 24.5% of pT1a, 51.9% of pT1b, and 63.3% of pT1c patients who were treated systemically after surgery. OS in pT1b (logrank test; p = 0.03) and DFS in pT1c (logrank test; p < 0.001) were significantly improved in treated compared with untreated patients. In the Cox proportional hazards model, treated patients had significantly longer OS than untreated patients in pT1b (hazard ratio (HR) 0.20) and pT1c (HR 0.54) groups. Estrogen receptor-negative tumors was also a significant predictor of survival in pT1c (HR 2.01) but not pT1ab patients. Furthermore, HR was greater in patients aged ≤ 35 years (3.18) compared to that in patients aged 50-69 years in the pT1b group.

Conclusions: NCD data revealed that systemic treatment improved OS in pT1bc but not in pT1a node-negative HER2+ breast cancer patients. Future observational research using big-sized data is expected to play an important role in optimizing treatment for patients with early-stage breast cancer.
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http://dx.doi.org/10.1007/s10549-019-05413-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6817748PMC
December 2019

Current conditions and issues of physicians and working conditions at institutions accredited by the Japanese Breast Cancer Society.

Breast Cancer 2020 Mar 22;27(2):159-165. Epub 2019 Aug 22.

Division of Oncologic Pathology, Department of Pathology and Microbiology, Nihon University School of Medicine, 30-1, Oyaguchikami-cho, Itabashi-ku, Tokyo, 173-8610, Japan.

Background: In Japan, with the rapid increase of breast cancer patients, there has been increasing demand for breast cancer treatment. As the main workforce for breast cancer treatment, women physicians are thought to be in key positions, since the number of women physicians has recently been increasing.

Methods: To clarify the current statuses and issues of physicians and work conditions at the accredited breast cancer care facilities, a survey was conducted by the Japanese Breast Cancer Society (JBCS).

Results: The main workforces engaged in breast cancer care are surgeons, and the number of breast surgeons of all institutions in this survey was 1338 (full time 1124, part time 214). The percentages of women among surgeons, breast specialists accredited by the JBCS, and residents are 22%, 25%, and 38%, respectively. Among breast specialists, more women tended to work at university hospitals and cancer hospitals. Twenty-eight percent of women were married and among those, 76% had at least one child. Many hospitals allow short working hours or exemption from in-house call for women surgeons during pregnancy and child-rearing. In contrast, half of the facilities apply a "single doctor-in-charge system", where the patient's primary physician has to be on-call every day. Many institutions convene conferences for breast cancer treatment planning before or after the scheduled working hours.

Conclusions: Current systems for treatment of breast cancer should be improved so that all surgeons specializing in the breast can develop their career while maintaining their personal life.
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http://dx.doi.org/10.1007/s12282-019-01005-xDOI Listing
March 2020

Dummy-run for standardizing plan quality of intensity-modulated radiotherapy for postoperative uterine cervical cancer: Japan Clinical Oncology Group study (JCOG1402).

Radiat Oncol 2019 Jul 29;14(1):133. Epub 2019 Jul 29.

Radiation Therapy Center, Okinawa Chubu Hospital, Okinawa, 904-2293, Japan.

Background: The purpose of this study was to assess compliance with treatment planning in a dummy-run for a multicenter clinical trial involving patients with high-risk postoperative uterine cervical cancer using intensity-modulated radiation therapy (IMRT) (JCOG1402 trial).

Methods: For the dummy-run, we prepared a computed tomography dataset comprising two anonymized cases of post-hysterectomy cervical cancer. These were sent to the 47 participating institutions to assess institutional plan quality such as delineations and dose distributions.

Results: Central review showed 3 and 4 deviations per treatment plan on average. The deviations related to the nodal and vaginal cuff clinical target volume (CTV) delineation, which accounted for approximately 50% of the total deviations. The CTV vaginal cuff showed considerable differences in delineation compared with the nodal CTV. For the Dice similarity coefficient, case 1 showed a mean ± 1σ of 0.81 ± 0.03 and 0.60 ± 0.09 for the nodal and the CTV vaginal cuff, respectively, while these were 0.81 ± 0.04 and 0.54 ± 0.14, respectively, for case two. Of the 47 institutions, 10 were required to resubmit their treatment plan because the delineations, planning target volume margin, and required dose distributions were not in accordance with the JCOG1402 protocol.

Conclusions: The dummy-run test in postoperative uterine cervical cancer demonstrated substantial deviations in the delineations, particularly for the CTV vaginal cuff. The analysis data could provide helpful information on delineation and planning, allowing standardization of IMRT planning for postoperative uterine cervical cancer.

Trial Registration: Japanese Clinical Trial Registry #: UMIN000027017 at https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000030672;language=J.
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http://dx.doi.org/10.1186/s13014-019-1340-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6664568PMC
July 2019

Artificial ascites for organs at risk sparing in intrapelvic brachytherapy: a case report of recurrent uterine cervical carcinoma adjacent to the bowel.

BJR Case Rep 2019 Feb 11;5(1):20180067. Epub 2018 Aug 11.

Department of Radiation Oncology, National Cancer Center Hospital, Tokyo, Japan.

Artificial ascites has been reported as an effective technique to reduce the risk of thermal injury in radiofrequency ablation of liver tumors by increasing the distance of collateral organs located next to the ablated sites. In this case report we share our experience with artificial ascites in an attempt to reduce the toxicity of collateral adjacent organs in the setting of re-irradiation for recurrent cervical cancer. A 52-year-old female who developed local recurrence after definitive radiation therapy was treated with interstitial re-irradiation by means of image-guided, (single-implant/multi fraction) high-dose-rate brachytherapy. Because the sigmoid colon was in close proximity to the recurrent tumor lesion, artificial ascites was generated before each treatment fraction by percutaneous injection of a defined amount of saline solution through the abdominal wall to create additional space between the two volumes. Artificial ascites showed a dosimetric improvement by reducing the sigmoid colon D per fraction from 286 cGy before to 189 cGy after saline injection. No severe complication was associated with the injection procedure.
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http://dx.doi.org/10.1259/bjrcr.20180067DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6519505PMC
February 2019

Role of Postmastectomy Radiotherapy After Neoadjuvant Chemotherapy in Breast Cancer Patients: A Study from the Japanese Breast Cancer Registry.

Ann Surg Oncol 2019 Aug 17;26(8):2475-2485. Epub 2019 May 17.

Department of Breast and Endocrine Surgery, Tokai University School of Medicine, Isehara, Japan.

Background: The role of postmastectomy radiotherapy (PMRT) in breast cancer patients receiving neoadjuvant chemotherapy (NAC) is controversial. We aimed to evaluate the effectiveness of radiotherapy in patients treated with NAC and mastectomy in the Japanese Breast Cancer Registry.

Methods: We enrolled patients who received NAC and mastectomy for cT1-4 cN0-2 M0 breast cancer. We evaluated the association between radiotherapy and outcomes, locoregional recurrence (LRR), distant disease-free survival (DDFS), and overall survival (OS) based on ypN status by multivariable analysis.

Results: Of the 145,530 patients, we identified 3226 who met the inclusion criteria. Among ypN1 patients, no differences were found in LRR, DDFS, or OS between groups with and without radiotherapy (p = 0.72, p = 0.29, and p = 0.36, respectively). Radiotherapy was associated with improved LRR-free survival (p < 0.001), DDFS (p = 0.01), and OS (p < 0.001) in patients with ypN2-3. Multivariable analysis demonstrated that use of radiotherapy was independently associated with improved LRR [hazard ratio (HR) 0.61, 95% confidence interval (CI) 0.45-0.82, p = 0.001] and OS [HR 0.69, 95% CI 0.53-0.89, p = 0.004) for ypN2-3 patients only. The association between radiotherapy and OS was not statistically significant among ypN0 (p = 0.22) and ypN1 patients (p = 0.51).

Conclusions: The results from this nationwide database study did not show significant associations between PMRT and improved survival among ypN0 and ypN1 patients. Radiotherapy may be beneficial only for ypN2-3 breast cancer patients who receive NAC and mastectomy in the modern era.
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http://dx.doi.org/10.1245/s10434-019-07453-1DOI Listing
August 2019

[On-line Adaptive Radiotherapy Using MRI-Guided Technique].

Igaku Butsuri 2019;38(4):159-165

Department of Radiation Oncology, National Cancer Center Hospital.

In our institution, we installed MRI-guided radiotherapy system (MRIdian, ViewRay Inc.), allowing to perform on-line adaptive radiotherapy (ART). The MRIdian has three Co sources with 120 degrees apart, equipped with MRI system using a static magnetic field of 0.35 T. The tumor can be monitored and identified in real-time Cine-MRI during treatments, and gated-radiotherapy is possible based on the boundaries. On-line ART can provide the optimum delivery where high dose coverages to the tumor and sparing dose to health organs can be achieved. However, patient specific QA in on-line ART has a limitation of activities, because patients stay in the couth while planning. In this report, we summarized the commissioning of the MRIdian, and the patient specific QA established in on-line ART was described.
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http://dx.doi.org/10.11323/jjmp.38.4_159DOI Listing
July 2019

Dependence of neutrons generated by Li(p,n) reaction on Li thickness under free-air condition in accelerator-based boron neutron capture therapy system employing solid-state Li target.

Phys Med 2019 Feb 16;58:121-130. Epub 2019 Feb 16.

Department of Medical Physics, National Cancer Center Hospital, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan; Division of Research and Development for Boron Neutron Capture Therapy, National Cancer Center Exploratory Oncology Research & Clinical Trial Center, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan; Department of Radiation Oncology, National Cancer Center Hospital, Tsukiji 5-1-1, Chuo-ku, Tokyo 104-0045, Japan.

Purpose: An accelerator-based boron neutron capture therapy (BNCT) system with a solid-state Li target is reported to have degradation of the Li target. The degradation reduces the Li thickness, which may change spectra of the generated neutrons corresponding to the Li thickness. This study aims to examine the relationship between the Li thickness and the generated neutrons and to investigate the effects of the Li thickness on the absorbed dose in BNCT.

Method: The neutron energy spectra were calculated via Monte Carlo simulation for Li thicknesses ranging from 20 to 150 μm. Using the system, the saturated radioactivity of gold induced by reactions between Au and the generated neutrons was evaluated with the simulation and the measurement, and those were compared. Additionally, for each Li thickness, the saturated radioactivity was compared with the number of generated neutrons. The absorbed doses delivered by B(n,α)Li, N(n,p)C, H(n, g)H, and (n,n') reactions in water were also calculated for each Li thickness.

Results: The measurement and simulation indicated a reduction in the number of neutrons due to the degradation of the Li target. However, the absorbed doses were comparable for each Li thickness when the requisite number of neutrons for BNCT was delivered. Additionally, the saturated radioactivity of Au could be a surrogate for the number of neutrons even if the Li thickness was varied.

Conclusions: No notable effect to the absorbed dose was observed when required neutron fluence was delivered in the BNCT even if the degradation of the Li was observed.
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http://dx.doi.org/10.1016/j.ejmp.2019.02.010DOI Listing
February 2019

Breast Cancer in Lean Postmenopausal Women Might Have Specific Pathological Features.

In Vivo 2019 Mar-Apr;33(2):483-487

Deartment of Breast Oncology, Juntendo University School of Medcine, Tokyo, Japan.

Background/aim: The rate of obesity, an independent risk factor for breast cancer in post-menopausal women, is quite low in Japan, indicating breast cancer in lean women to be more common in the Japanese than in Westerners. However, biological characteristics of such breast cancers have not been adequately investigated.

Patients And Methods: We retrospectively investigated clinicopathological breast cancer features of 566 postmenopausal Japanese women, who underwent curative surgery, in relation to patient physique based on the body mass index.

Results: There were no differences in several factors examined such as tumour size according to patient physique. On the other hand, mean values of the Ki67 labelling index were significantly higher in lean compared to obese patients (p=0.027). Likewise, HER2-positive tumours were more often observed in lean patients (p=0.051).

Conclusion: Lean postmenopausal women had more aggressive tumours, apparently contradicting the widely held view for breast cancer in obese women.
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http://dx.doi.org/10.21873/invivo.11499DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6506305PMC
June 2019

Monte Carlo modeling of a 60Co MRI-guided radiotherapy system on Geant4 and experimental verification of dose calculation under a magnetic field of 0.35 T.

J Radiat Res 2019 Jan;60(1):116-123

Department of Radiation Oncology, National Cancer Center Hospital, 5-1-1 Tsukiji, Chuo-ku, Tokyo, Japan.

Our purpose was to establish the commissioning procedure of Monte Carlo modeling on a magnetic resonance imaging-guided radiotherapy system (MRIdian, Viewray Inc.) under a magnetic field of 0.345 T through experimental measurements. To do this, we sought (i) to assess the depth-dose and lateral profiles generated by the Geant4 using either EBT3 film or the BJR-25 data; (ii) to assess the calculation accuracy under a magnetic field of 0.345 T. The radius of the electron trajectory caused by the electron return effect (ERE) in a vacuum was obtained both by the Geant4 and the theoretical methods. The surface dose on the phantom was calculated and compared with that obtained from the film measurements. The dose distribution in a phantom having two air gaps was calculated and measured with EBT 3 film. (i) The difference of depth-dose profile generated by the Geant4 from the BJR-25 data was 0.0 ± 0.8% and 0.3 ± 1.5% for field sizes of 4.5 and 27.3 cm2, respectively. Lateral dose profiles generated by Geant4 agreed well with those generated from the EBT3 film data. (ii) The radius of the electron trajectory generated by Geant4 agreed well with the theoretical values. A maximum of ~50% reduction of the surface dose under a magnetic field of 0.345 T was observed due to elimination of the electron contamination caused by the magnetic field, as determined by both the film measurements and the Geant4. Changes in the dose distributions in the air gaps caused by the ERE were observed on the Geant4 and in the film measurements. Gamma analysis (3%/3 mm) showed a pass rate of 95.1%. Commissioning procedures for the MRI-guided radiotherapy system on the Geant4 were established, and we concluded that the Geant4 had provided high calculation accuracy under a magnetic field of 0.345 T.
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http://dx.doi.org/10.1093/jrr/rry087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6373691PMC
January 2019

[Efforts toward Patient Safety: Development of System and Education of Non-Technical Skill].

Igaku Butsuri 2018;38(2):62-67

Department of Radiation Oncology, National Cancer Center Hospital.

Advanced radiotherapy such as intensity-modulated radiotherapy offers many advantages of high accuracy and efficiency of radiotherapy. To date, many technical guidelines with description of quality assurance and quality control have been reported. However, some reports indicated that human factor and environment is major cause of radiotherapy incidents. If radiotherapy systems depend on automation and computer system, individual risk management is degraded and ability of preventing radiotherapy incidents weaken. Recently, the American Association of Physicists in Medicine (AAPM) task group-100 was reported and it has a new concept guideline, which proposed the comprehensive risk management and education of non-technical skills for overall radiotherapy processes. The TG-100 recommends implementation of process map, reporting system, risk assessment such as failure mode and effects analysis (FMEA) and fault tree analysis (FTA) especially for advanced radiotherapy. In this paper, we described effective and efficient procedures to improve the treatment processes and education of non-technical skills using the such management tools proposed by the TG-100 guide-lines.
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http://dx.doi.org/10.11323/jjmp.38.2_62DOI Listing
June 2019

Analysis of circulating tumour cell and the epithelial mesenchymal transition (EMT) status during eribulin-based treatment in 22 patients with metastatic breast cancer: a pilot study.

J Transl Med 2018 10 20;16(1):287. Epub 2018 Oct 20.

Department of Breast Oncology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.

Background: Liquid biopsy approaches, such as measuring circulating tumour cells (CTCs), have recently been introduced in several clinical studies. However, the development of CTCs as a predictive marker for treatment effects on breast cancer remains an enormous task. We investigated CTCs, including epithelial mesenchymal transition (EMT) status, from metastatic breast cancer patients who had received eribulin-based treatment, which reportedly suppresses EMT as a means of tumour suppression. Our aim was to test the possibility of this method serving as a tool predicting eribulin efficacy.

Methods: Twenty-two patients were enrolled and peripheral blood samples were collected before eribulin treatment. CTCs were then examined using a Microfluidic Chip device. CTCs positive for vimentin and pan-cytokeratin were defined as mesenchymal and epithelial CTCs, respectively. Progression-free survival (PFS) and clinical response were assessable in 20 and 18 patients, respectively, in relation to the number of CTCs.

Results: Numbers of total CTCs were significantly increased in patients with progressive disease during treatment (p = 0.006). Median PFS was 14.6 weeks and patients with more total and mesenchymal CTCs at baseline had significantly shorter PFS (p = 0.0013 and 0.013, respectively). Multivariate logistic regression analysis revealed small number of total baseline CTCs and long disease-free survival to be related to long PFS (p = 0.0004 and 0.020, respectively).

Conclusions: Our data suggest that determining both mesenchymal and epithelial CTCs at baseline might be a good tool for predicting eribulin responsiveness. Evaluation of mesenchymal CTC can be considered as a parameter in larger studies, while most clinical trials are currently employing only the detection of the epithelial cellular adhesion molecule (EpCAM).
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http://dx.doi.org/10.1186/s12967-018-1663-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6195982PMC
October 2018

Establishment of postal audit system in intensity-modulated radiotherapy by radiophotoluminescent glass dosimeters and a radiochromic film.

Phys Med 2018 Apr 24;48:119-126. Epub 2018 Apr 24.

Department of Radiation Oncology, Kindai University Faculty of Medicine, Osaka 589-8511, Japan.

We developed an efficient postal audit system to independently assess the delivered dose using radiophotoluminescent glass dosimeters (RPLDs) and the positional differences of fields using EBT3 film at the axial plane for intensity-modulated radiotherapy (IMRT). The audit phantom had a C-shaped target structure as a planning target volume (PTV) with four measurement points for the RPLDs and a cylindrical structure as the organ at risk (OAR) for one measurement point. The phantoms were sent to 24 institutions. Point dose measurements with a 0.6 cm PTW farmer chamber were also performed to justify glass dosimetry in IMRT. The measured dose with the RPLDs was compared to the calculated dose in the institution's treatment planning system (TPS). The mean ± 1.96σ of the ratio of the measured dose with the RPLDs to the farmer chamber was 0.997 ± 0.024 with no significant difference (p = .175). The investigations demonstrated that glass dosimetry was reliable with a high measurement accuracy comparable to the chamber. The mean ± 1.96σ for the dose differences with a reference of the TPS dose for the PTV and the OAR was 0.1 ± 2.5% and -2.1 ± 17.8%, respectively. The mean ± 1.96σ for the right-left and the anterior-posterior direction was -0.9 ± 2.8 and 0.5 ± 1.4 mm, respectively. This study is the first report to justify glass dosimetry for implementation in IMRT audit in Japan. We demonstrate that our postal audit system has high accuracy with a high-level criterion of 3%/3 mm.
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http://dx.doi.org/10.1016/j.ejmp.2018.03.013DOI Listing
April 2018
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