Radiotherapy for stage I and II testicular seminomas: Secondary malignancies and survival

Introduction: Testicular seminoma affects relatively young men with excellent survival outcomes. There has been increasing concern that radiotherapy (RT) leads to secondary malignant neoplasms (SMNs) and subsequent mortality. We evaluated the effect of RT on incidence of SMNs and quantified cancer-related mortality and other causes of death for patients with stage I and II testicular seminoma. Material and methods: A national sample of men (1988-2013) diagnosed with stage IA/IB/IS/IIA/IIB/IIC testicular seminomas from Surveillance, Epidemiology, and End Results were evaluated. Use of RT over time and survival curves (5/10/15-year) was stratified by stage. Log-binomial regression determined relative risk of developing SMNs. Incidence rate ratios (IRR) and age-adjusted Cox proportional hazards models compared overall, cancer-specific survival (CSS), and other cancer-specific survival. Competing-risks regression generated cumulative incidence functions. Prevalence ratios explored excess deaths owing to specific causes. Results: A total of 16,463 men were included with 9,126 (55.4%) undergoing RT with markedly decreased use for stage I seminoma in recent years (<20%) and ~50% for stage IIA. RT increased risk of SMNs (relative risk = 1.84 [95% CI: 1.61-2.10, P<0.01]). Survival rates were excellent (15-year CSS for stage I [≥99%], stage IIA [98.1%], stage IIB-C [96%-97%]). RT was associated with improved CSS for stage IB and IIA, but demonstrated less benefit for stage IA (IRR = 0.63 [95% CI: 0.35-1.14, P = 0.10]) with worse other cancer-specific survival (IRR = 1.80 [95% CI: 0.97-3.59, P = 0.05]). Gastrointestinal, respiratory, urinary, and hematologic malignances accounted for 84% of SMN deaths. Conclusions: RT offers excellent CSS for men with stage I/II seminoma and an increased risk of SMN later in life. Future studies should better evaluate risk-stratification for stage IB patients.