Risk of Leukemia among Survivors of Testicular Cancer: A Population-Based Study of 40,576 Patients

Purpose Survivors of testicular cancer are at increased risk of developing leukemia. We quantify long-term temporal trends in excess absolute risk (EAR) and excess relative risk (ERR) of leukemia among testicular cancer survivors, using multivariate analyses to evaluate the effects of age at diagnosis, attained age, calendar year of testicular cancer diagnosis, time since diagnosis, and initial treatment. Methods A total of 40,576 1-year survivors of testicular cancer were identified within 14 population-based cancer registries in Europe and North America between January 1, 1943 and December 31, 2001. We used Poisson regression analysis to model EAR (per 100,000 person-years) and ERR of secondary leukemia. Cumulative risks were calculated using a competing risk model. Results Secondary leukemia (excluding chronic lymphocytic leukemia) developed in 89 patients (EAR=10.5, 95% confidence interval (CI)=7.3–14.3; ERR=1.5, 95% CI=1.0–2.1). Significantly elevated risks were observed for acute myeloid leukemia (AML) (EAR=7.1, 95% CI=4.6–10.1; ERR=2.0, 95% CI=1.3–2.9) and acute lymphoblastic leukemia (EAR=1.4, 95% CI=0.4–2.9; ERR=2.1, 95% CI=0.5–4.4). Risk of leukemia was highest during the first 5 years after testicular cancer diagnosis. In analyses adjusted for age at diagnosis and time since testicular cancer diagnosis, the risk of AML was non-significantly higher among patients whose initial management included chemotherapy compared to those who received radiotherapy alone (p=0.2). Cumulative risk of leukemia was approximately 0.23% by 30 years after testicular cancer diagnosis. Conclusion Although the relative risk of leukemia is large, the absolute risk and cumulative risk of leukemia following testicular cancer is small. Thus, improvements in survival due to treatment greatly outweigh the risk of this late effect.