J Natl Cancer Inst 2020 May 27. Epub 2020 May 27.
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD.
Background: Immunosuppressed solid organ transplant recipients [SOTRs] have elevated rates of certain rare cancers caused by viruses. Evaluating risk of rare cancers among SOTRs may provide etiological clues for additional cancers linked to poor immunity and viral infections.
Methods: We performed a cohort study of 262,455 SOTRs (1987-2014) from the US SOTR registry linked to 17 population-based cancer registries. First cancers in SOTRs were categorized using an established classification scheme based on site and histology. Standardized incidence ratios (SIRs) compared risk in SOTRs to the general population. We used Poisson regression to calculate incidence rate ratios (IRRs) according to immune-related SOTR characteristics, including time since transplant (i.e., duration of immunosuppression). All statistical tests are two-sided.
Results: We examined 694 distinct cancer subtypes, with 33 manifesting statistically significantly elevated SIRs (Bonferroni p < 7.2 x 10-5). All 33 are rare (incidence <6 per 100,000 person-years) and several have known viral etiology (e.g. Merkel cell carcinoma (SIR = 24.7, 95%CI = 20.8 to 29.1). Additional cancers that were increased include squamous cell carcinomas (SCCs) of the lip (SIR range = 18.3-19.8), eye/adnexa (SIR = 13.8, 95%CI = 7.9 to 22.3), salivary gland (SIR = 9.3, 95%CI = 6.1 to 13.5), and nasal cavity/sinuses (SIR = 4.5, 95%CI = 2.8 to 6.8); sebaceous adenocarcinoma (SIR = 34.3, 95%CI = 26.3 to 44.0); malignant fibrous histiocytoma (15.4); and subtypes of bladder, kidney, lung, and colon cancer (SIR range = 3.2-13.3). Incidence of several cancers increased over time since transplant (ptrend<0.05), including SCCs of the lip, salivary gland, and anogenital sites.
Conclusions: SOTRs experience elevated rates of several rare cancers. Because some of these cancers exhibit aggressive behavior with poor outcomes, it is important to further characterize the role of immunity and the potential involvement of oncogenic viruses to improve prevention and treatment.