Publications by authors named "Taran P Hellebust"

7 Publications

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Overall survival after initial radiotherapy for brain metastases; a population based study of 2140 patients with non-small cell lung cancer.

Acta Oncol 2021 Aug 25;60(8):1054-1060. Epub 2021 May 25.

Department of Oncology, Oslo University Hospital, Oslo, Norway.

Background: Brain metastases (BM) occur in about 30% of all patients with non-small cell lung cancer (NSCLC). BM treatment guidelines recommend more frequent use of stereotactic radiotherapy (SRT). Overall, studies report no difference in overall survival (OS) comparing SRT to whole-brain radiotherapy (WBRT). We examined survival after radiotherapy for BM in a population-based sample from the South-Eastern Norway Regional Health Authority treated 2006-2018.

Methods: We reviewed electronic medical records of 2140 NSCLC patients treated with SRT or WBRT for BM from 2006-2018. Overall survival (OS) was compared to predicted survival according to the prognostic systems DS-GPA and Lung-molGPA.

Results: Use of SRT increased during the period, from 19% (2006-2014) to 45% (2015-2018). Median OS for all patients was 3.0 months, increasing from 2.0 (2006) to 4.0 (2018). Median OS after SRT was 7.0 months ( = 435) and 3.0 months after WBRT ( = 1705). Twenty-seven percent of SRT patients and 50% of WBRT patients died within 90 days after start of RT. Age ≥70, male sex, KPS ≤70, non-adenocarcinoma histology, ECM present, multiple BM, and WBRT were associated with shorter survival ( < .001). Actual mOS corresponded best with predicted mOS by DS-GPA and Lung-molGPA for the SRT group.

Conclusion: Overall survival after radiotherapy (RT) for BM improved during the study period, but only for patients treated with SRT. Survival after WBRT remains poor; its use should be questioned. DS-GPA and Lung-molGPA seem most useful in predicting prognosis considered for SRT.
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August 2021

A Nordic-Baltic perspective on indications for proton therapy with strategies for identification of proper patients.

Acta Oncol 2020 Oct 9;59(10):1157-1163. Epub 2020 Sep 9.

Danish Center for Particle Therapy, Aarhus University Hospital, Denmark.

The beneficial effects of protons are primarily based on reduction of low to intermediate radiation dose bath to normal tissue surrounding the radiotherapy target volume. Despite promise for reduced long-term toxicity, the percentage of cancer patients treated with proton therapy remains low. This is probably caused by technical improvements in planning and delivery of photon therapy, and by high cost, low availability and lack of high-level evidence on proton therapy. A number of proton treatment facilities are under construction or have recently opened; there are now two operational Scandinavian proton centres and two more are under construction, thereby eliminating the availability hurdle. Even with the advantageous physical properties of protons, there is still substantial ambiguity and no established criteria related to which patients should receive proton therapy. This topic was discussed in a session at the Nordic Collaborative Workshop on Particle Therapy, held in Uppsala 14-15 November 2019. This paper resumes the Nordic-Baltic perspective on proton therapy indications and discusses strategies to identify patients for proton therapy. As for indications, neoplastic entities, target volume localisation, size, internal motion, age, second cancer predisposition, dose escalation and treatment plan comparison based on the as low as reasonably achievable (ALARA) principle or normal tissue complication probability (NTCP) models were discussed. Importantly, the patient selection process should be integrated into the radiotherapy community and emphasis on collaboration across medical specialties, involvement of key decision makers and knowledge dissemination in general are important factors. An active Nordic-Baltic proton therapy organisation would also serve this purpose.
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October 2020

Dose deviations induced by respiratory motion for radiotherapy of lung tumors: Impact of CT reconstruction, plan complexity, and fraction size.

J Appl Clin Med Phys 2020 Apr 12;21(4):68-79. Epub 2020 Mar 12.

Department of Medical Physics, Oslo University Hospital, Oslo, Norway.

A thorax phantom was used to assess radiotherapy dose deviations induced by respiratory motion of the target volume. Both intensity modulated and static, non-modulated treatment plans were planned on CT scans of the phantom. The plans were optimized using various CT reconstructions, to investigate whether they had an impact on robustness to target motion during delivery. During irradiation, the target was programmed to simulate respiration-induced motion of a lung tumor, using both patient-specific and sinusoidal motion patterns in three dimensions. Dose was measured in the center of the target using an ion chamber. Differences between reference measurements with a stationary target and dynamic measurements were assessed. Possible correlations between plan complexity metrics and measured dose deviations were investigated. The maximum observed motion-induced dose differences were 7.8% and 4.5% for single 2 Gy and 15 Gy fractions, respectively. The measurements performed with the largest target motion amplitude in the superior-inferior direction yielded the largest dosimetric deviations. For 2 Gy fractionation schemes, the summed dose deviation after 33 fractions is likely to be less than 2%. Measured motion-induced dose deviations were significantly larger for one CT reconstruction compared to all the others. Static, non-modulated plans showed superior robustness to target motion during delivery. Moderate correlations between the modulation complexity score applied to VMAT (MCSv) and measured dose deviations were found for 15 Gy SBRT treatment plans. Correlations between other plan complexity metrics and measured dose deviations were not found.
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April 2020

Ten-year survival after High-Dose-Rate Brachytherapy combined with External Beam Radiation Therapy in high-risk prostate cancer: A comparison with the Norwegian SPCG-7 cohort.

Radiother Oncol 2019 03 30;132:211-217. Epub 2018 Oct 30.

Department of Oncology, Oslo University Hospital, Norway.

Background: The survival benefit of dose-escalation with High-Dose-Rate brachytherapy (HDR-BT) boost combined with External Beam Radiotherapy (EBRT) for the treatment of high-risk prostate cancer (PCa) remains debatable. We investigated 10-year PCa-specific mortality (PCSM) and overall mortality (OM) in high-risk patients treated with HDR-BT/EBRT (calculated EQD2 = 102 Gy) compared to EBRT alone (70 Gy).

Methods: HDR-BT boosts (10 Gy × 2) were given 2 weeks apart followed by 50 Gy conformal EBRT (2 Gy × 25) to the prostate and seminal vesicles. The HDR-BT/EBRT group (N:325) received Androgen Deprivation Therapy for a median duration of 2 years. The historical control group (N:296), received a median dose of 70 Gy (2 Gy × 35) to the prostate and seminal vesicles with lifelong Anti-Androgen Treatment. For each treatment group PCSM and OM were established by competing-risk analyses and Kaplan-Meier analyses respectively. Differences were evaluated by the logrank test. Independent associations were established by Cox regression analyses. Significance level set to p < 0.05.

Results: Median follow-up was 104 and 120 months for the HDR-BT/EBRT and the EBRT group respectively. A 3.6-fold decreased risk of PCSM (p < 0.01) and a 1.6-fold decreased risk of OM (p = 0.02) in the HDR-BT/EBRT cohort compared to the EBRT-only group were revealed. Ten-year OM and PCSM rates were 16% and 2.5% in the HDR-BT/EBRT group versus 23% and 8.2% in the EBRT-only group respectively. Both treatment modality (HR = 3.59, 95%CI 1.50-8.59) and Gleason score (HR = 2.48, 95%CI 1.18-5.21) were associated with PCSM. Only treatment modality (HR = 1.63, 95%CI = 1.08-2.44) was significantly associated with OM.

Conclusions: Men with high-risk PCa have a significantly reduced PCSM and OM rates when treated with dose-escalated radiotherapy achieved by HDR-BT/EBRT compared to EBRT alone (70 Gy). A Gleason score of 8-10 was independently associated with increased risk of PCSM. Randomized studies are warranted.

Summary: Observational study of 10-year survival in high-risk Prostate Cancer (PCa) after High-Dose-Rate brachytherapy combined with External Beam Radiation Therapy (HDR-BT/EBRT) compared to EBRT alone. The combined HDR-BT/EBRT treatment was found to give a 3.6-fold decrease in Prostate Cancer Specific Mortality (PCSM) and a 1.6-fold decrease in Overall Mortality (OM). Gleason score and type of treatment strongly influenced PCSM whereas only treatment modality was associated with OM. The observed benefits of dose-escalation warrant future randomized trials.
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March 2019

Long-term outcomes after pelvic radiation for early-stage endometrial cancer.

J Clin Oncol 2013 Nov 9;31(31):3951-6. Epub 2013 Sep 9.

Mathias Onsrud, Taran P. Hellebust, Claes G. Tropé, and Gunnar B. Kristensen, Norwegian Radium Hospital, Oslo University Hospital; Mathias Onsrud, Milada Cvancarova, Taran P. Hellebust, and Claes G. Tropé, University of Oslo, Oslo; Taran P. Hellebust, Norwegian Radiation Protection Authority, Østerås; and Kristina Lindemann, Akershus University Hospital, Lørenskog, Norway.

Purpose: This follow-up of a randomized study was conducted to assess the long-term effects of external beam radiation therapy (EBRT) in the adjuvant treatment of early-stage endometrial cancer.

Patients And Methods: Between 1968 and 1974, 568 patients with stage I endometrial cancer were included. After primary surgery, patients were randomly assigned to either vaginal radium brachytherapy followed by EBRT (n = 288) or brachytherapy alone (n = 280). Overall survival was analyzed by using the Kaplan-Meier method. A Cox proportional hazards model was used to estimate hazard ratios (HRs) with 95% CIs. We also conducted analyses stratified by age groups.

Results: After median 20.5 years (range, 0 to 43.4 years) of follow-up, no statistically significant difference was revealed in overall survival (P = .186) between treatment groups. However, women younger than age 60 years had significantly higher mortality rates after EBRT (HR, 1.36; 95% CI, 1.06 to 1.76) than the control group. The risk of secondary cancer increased after EBRT, especially in women younger than age 60 years (HR, 2.02; 95% CI, 1.30 to 3.15).

Conclusion: We observed no survival benefit of external pelvic radiation in early-stage endometrial carcinoma. In women younger than age 60 years, pelvic radiation decreased survival and increased the risk of secondary cancer. Adjuvant EBRT should be used with caution, especially in women with a long life expectancy.
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November 2013

A multicentre comparison of the dosimetric impact of inter- and intra-fractional anatomical variations in fractionated cervix cancer brachytherapy.

Radiother Oncol 2013 Apr 18;107(1):20-5. Epub 2013 Apr 18.

Department of Radiotherapy and Oncology, Comprehensive Cancer Center, Medical University of Vienna, Austria.

Background And Purpose: To compare the dosimetric impact of organ and target variations relative to the applicator for intracavitary brachytherapy by a multicentre analysis with different application techniques and fractionation schemes.

Material And Methods: DVH data from 363 image/contour sets (120 patients, 6 institutions) were included for 1-6 fractions per patient, with imaging intervals ranging from several hours to ∼20 days. Variations between images acquired within one (intra-application) or between consecutive applicator insertions (inter-application) were evaluated. Dose plans based on a reference MR or CT image series were superimposed onto subsequent image sets and D(2cm(3)) for the bladder, rectum and sigmoid and D(90) for HR CTV were recorded.

Results: For the whole sample, the systematic dosimetric variations for all organs at risk, i.e. mean variations of D(2cm(3)), were found to be minor (<5%), while random variations, i.e. standard deviations were found to be high due to large variations in individual cases. The D(2cm(3)) variations (mean±1SD) were 0.6±19.5%, 4.1±21.7% and 1.6±26.8%, for the bladder, rectum and sigmoid. For HR CTV, the variations of D90 were found to be -1.1±13.1% for the whole sample. Grouping of the results by intra- and inter-application variations showed that random uncertainties for bladder and sigmoid were 3-7% larger when re-implanting the applicator for individual fractions. No statistically significant differences between the two groups were detected in dosimetric variations for the HR CTV. Using 20% uncertainty of physical dose for OAR and 10% for HR CTV, the effects on total treatment dose for a 4 fraction HDR schedule at clinically relevant dose levels were found to be 4-8 Gy EQD2 for OAR and 3 Gy EQD2 for HR CTV.

Conclusions: Substantial variations occur in fractionated cervix cancer BT with higher impact close to clinical threshold levels. The treatment approach has to balance uncertainties for individual cases against the use of repetitive imaging, adaptive planning and dose delivery.
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April 2013

Modeling volume effects of experimental brachytherapy in the rat rectum: uncovering the limitations of a radiobiologic concept.

Int J Radiat Oncol Biol Phys 2002 Jul;53(4):1014-22

Department of Surgical Oncology, The Norwegian Radium Hospital, University of Oslo, Oslo, Norway.

Purpose: To analyze the significance of volume effects in experimental brachytherapy, based on modeling normal tissue complication probability.

Methods And Materials: Experimental brachytherapy in the rat rectum was based on an eight-step 2.5-mm step size source configuration for 192Ir, afterloaded into an unshielded polystyrene applicator. Volume effects were studied using a half-circumferential lead-shielded applicator and a shorter (two-step) source configuration. The main end point was rectal stenosis.

Results: Rectal stenosis was always caused by a radiation ulcer. With the shielded configuration, single-dose ED50 (50% incidence of rectal stenosis) increased from 23 Gy to 36.5 Gy. Single-dose ED50 for the short configuration was 77.9 Gy. The data showed a reasonable fit to a three-parameter version of the biophysical model described by Jackson et al. (1995). This model assumes that organs consist of a large number of radiobiologically independent subunits and that radiation causes a complication if the fraction of the organ damaged is greater than its functional reserve. The fraction of the organ damaged is calculated summing over fractions of the organ damaged at each dose level. The calculated mean functional reserve (nu50) of the rat rectum, assuming a cumulative functional reserve distribution in the group of experimental rats, was 0.53.

Conclusions: The volume effect observed within small brachytherapy volumes agreed well with clinical experience of large tolerance doses in contact X-ray therapy. However, the nu50 value was comparable to the high functional reserve value reported for liver. Experimental volume effects probably reflect repair processes originating in the areas adjacent to small radiation fields of brachytherapy more than the radiobiologic characteristics of the cells in the irradiated volume.
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July 2002