Impact of modern treatment strategies on second cancer incidence for patients with early stage seminoma: A population-based study in British Columbia.

Abstract

423 Background: The purpose of this study is to examine the incidence of Second Cancers (SC) in patients with Stage I or II Seminoma treated in British Columbia (BC), and compare rates between patients managed with Radiation Therapy, Chemotherapy, or Active Surveillance. Methods: Consecutive patients with Stage I or II Seminoma (n = 1549, 21167 person years) diagnosed in British Columbia between 1984 and 2013 were identified from the BC Cancer Registry and included in this study. Patients were managed with Radiation Therapy (RT; n = 663), Chemotherapy (CT; n = 259) or Active Surveillance (AS; n = 624). Data was extracted from the registry and verified by individual patient chart review. Cumulative incidence rates were computed using competing risk analysis. Age and Sex Standardized Incidence Ratios (ASIR) were calculated (compared to the Canadian population). Results: After a median follow-up of 14 years (RT group: 21.5yrs, CT group: 10yrs, AS group: 8yrs), the 15 year Overall Survival was 91.4%. Only 15 patients died from progressive Seminoma, while 46 died from second cancers. A total of 115 patients developed SCs, and the cumulative incidence (CI) of SC, at 15 years, was: 5.9% for patients who received RT, 8.6% for those who had CT, and 4.9% for patients managed with AS. The higher CI for patients treated with CT, versus RT, was not statistically significant (p = 0.08). The ASIR for RT, CT and AS groups were 1.31 (95% Confidence Intervals: 0.92- 1.86), 2.57 (1.07- 6.15; p = 0.03), and 1.38 (0.75- 2.54), respectively. Patients who underwent treatment at ages 30-44yr and 45-59yr had a significantly higher ASIRs of 4.33 (2.1- 8.9; p < 0.001) and 1.8 (1.16- 2.8; p = 0.008). ASIR was not significantly different when stratified by radiation dose, field types, or year of diagnosis. Conclusions: We found no statistically significant difference in the Cumulative Incidence of Second Cancers for patients treated with Radiation Therapy versus Chemotherapy in our patient population. Longer follow-up for the CT group is required to confirm trends evident in our analysis.