This study was undertaken to determine the effect of treatment for childhood cancer on male fertility. We reviewed the fertility of male Childhood Cancer Survivor Study survivor and sibling cohorts who completed a questionnaire. We abstracted the chemotherapeutic agents administered, the cumulative dose of drug administered for selected drugs, and the doses and volumes of all radiation therapy from medical records. Risk factors for siring a pregnancy were evaluated using Cox proportional hazards models. The 6,224 survivors age 15 to 44 years who were not surgically sterile were less likely to sire a pregnancy than siblings (hazard ratio [HR], 0.56; 95% CI, -0.49 to 0.63). Among survivors, the HR of siring a pregnancy was decreased by radiation therapy of more than 7.5 Gy to the testes (HR, 0.12; 95% CI, -0.02 to 0.64), higher cumulative alkylating agent dose (AAD) score or treatment with cyclophosphamide (third tertile HR, 0.42; 95% CI, -0.31 to 0.57) or procarbazine (second tertile HR, 0.48; 95% CI, -0.26 to 0.87; third tertile HR, 0.17; 95% CI, -0.07 to 0.41). Compared with siblings, the HR for ever siring a pregnancy for survivors who had an AAD score = 0, a hypothalamic/pituitary radiation dose = 0 Gy, and a testes radiation dose = 0 Gy was 0.91 (95% CI, 0.73 to 1.14; P = .41). This large study identified risk factors for decreased fertility that may be used for counseling male cancer patients.
