Background: Men with testicular cancer have an increased risk of developing cancer in the contralateral testis, but the risks of second gonadal cancers (SGCs) in women and children treated for germ cell tumors (GCTs) have not previously been quantified.
Methods: The incidence of SGCs was ascertained in patients who had survived for at least 1 year after GCT diagnosis using data from the Surveillance, Epidemiology, and End Results SEER 9 registries (1980-2012). Relative risks of SGCs were estimated separately for boys, women, and girls compared with men based on Poisson regression analysis.
Results: The cohort included 21,546 individuals (1116 boys, 827 women, 622 girls, and 18,981 men). A total of 25 SGCs were identified in boys, 1 in women, and 2 in girls compared with 254 in men. The risk of SGC in postpubertal boys (aged ≥10 years) was comparable to that of adult men (boys: standardized incidence ratio, 15.90; 95% confidence interval, 10.29-23.47; men: standardized incidence ratio, 10.88; 95% confidence interval, 9.58-12.30). However, no SGCs were observed in boys who were diagnosed with a testicular GCT before age 10 years (N = 179). An elevated risk of SGC was also not observed for women or girls.
Conclusions: The apparent lack of an SGC in prepubertal boys suggests that susceptibility is either age-dependent and/or histology-dependent. The sex differences in the risk of SGC suggest differences in the etiology of ovarian versus testicular GCT. The finding that the risk of SGCs in postpubertal boys is similar to that observed in men indicates that long-term follow-up for SGC is warranted in postpubertal boys. Cancer 2016;122:2076-82. © 2016 American Cancer Society.
Keywords: Epidemiology; Surveillance; and End Results (SEER); epidemiology; germ cell tumor; pediatrics; second cancer; testicular cancer.
© 2016 American Cancer Society.