Abstract: PD53-05
Sources of Funding: none

Introduction

Testicular seminoma is the most radiosensitive genitourinary malignancy and affects relatively young men with excellent survival outcomes. Given the long life expectancy among survivors, there has been increasing concern regarding the impact of radiation therapy on development of secondary malignancies and potential mortality. We aimed to quantify the impact of radiation after orchiectomy for seminoma on survival, incidence of secondary malignancy, and eventual causes of death.

Methods

A national sample of men (1988-2013) diagnosed with stage 1A, 1B, 1S, 2A, 2B, and 2C testicular seminomas from Surveillance, Epidemiology, and End Results Program registries were evaluated. Kaplan-Meier curves estimated 5, 10, and 15-year overall (OS) and cancer-specific survival (CSS). Men receiving frontline radiation therapy were identified, and Cox proportional hazards models estimated impact on OS and CSS. Log-binomial regression estimated risk of secondary malignancy after radiation therapy. Causes of death were quantified, and excess deaths from secondary malignancies associated with radiation therapy were identified.

Results

A total of 17830 men (median age 37, 76% Caucasian, 15% Hispanic) with testicular seminomas were included for survival analysis of whom 16969 (95%) had data on radiation therapy and no prior history of malignancy. Over 50% of men with stage 1A, 1B, and 2A seminoma underwent radiation therapy. Survival rates were generally excellent (10-year CSS 1A (99.5%), 1B (99.5%), 2A (98.2%), 2B (97.3%), 2C (96.8%), 1S (99.1%)); improvement in OS was observed with radiation therapy for stage 1 (HR 0.59 (95%CI 0.50-0.70), p<0.001)) and stage 2A (HR 0.29 (95%CI 0.13-0.67), p<0.004) disease. No benefit was observed for stage 2B (p=0.70) and 2C (p=0.91) disease. The most common causes of death were cardiovascular/peripheral vascular disease (N=131), testicular cancer (N=116), other cancer (N=115), and accident/suicide/homicide (N=107). Radiation increased risk of secondary malignancy (RR 1.78 (1.56-2.04), p<0.001) and relative proportion of deaths from other cancers (0.90% vs. 0.41% for no radiation) with most notable differences for respiratory (prevalence ratio (PR) 2.5), gastrointestinal (PR 1.7), lymphoma/leukemia (PR 1.5), and other visceral cancers. For stage 1A (radiation vs. no radiation), the increase in absolute proportion of deaths from other cancers (0.98% vs. 0.28%, p<0.001) was not offset by any reduction in cancer deaths (0.55% vs. 0.46%, p=0.502).

Conclusions

In a national sample of men, survival rates for testicular seminoma were excellent with increased incidence of secondary malignancies associated with radiation therapy. While deaths due to other cancers was increased, the relative survival benefit of radiation therapy for stage 1B, 1S, and 2A testicular seminoma appeared to outweigh the risks but not for stage 1A.

Funding

none