To define demographic and therapeutic associations with the risk of breast cancer in children treated for Hodgkin's disease (HD), particularly the frequency and interval to the development of contralateral breast cancer.

All 398 female patients (<19 years) treated for HD in five institutions during the accrual period were evaluated. Mean follow-up was 16.9 years. The standardized incidence ratio (SIR) was calculated as the ratio of the observed number of cases to the expected number of cases, estimated using age-matched controls from the Surveillance, Epidemiology, and End Results database.

A total of 29 women developed breast cancer (25 invasive, 4 ductal carcinoma in situ; SIR, 37.25; 95% confidence interval, 24.96-53.64). Time to diagnosis was 9.4 to 36.1 years. Cumulative incidence was 24% at 30 years. Ten patients (34%) had bilateral disease (9 metachronous, 1 synchronous). The interval to contralateral breast cancer was 12 to 34 months. On univariate analysis, significant variables included stage of HD, mantle radiation dose, pelvic radiation (protective), and follow-up time. On multivariate analysis, early stage and older age at diagnosis of HD (12 years) were significant predictors of secondary breast cancer.

Women surviving pediatric HD were found to have a 37-fold increase in the risk of breast cancer and a high likelihood of rapidly developing bilateral disease. Early-stage HD and age greater than 12 years at diagnosis of HD were independent risk factors. Higher radiation doses may augment risk, and pelvic radiation may be protective. Breast cancer screening methodology and frequency, plus the role of prophylaxis in patients with unilateral disease, require definition.