Breast cancer risk in female survivors of Hodgkin's lymphoma: lower risk after smaller radiation volumes.

Abstract

We assessed the long-term risk of breast cancer (BC) after treatment for Hodgkin's lymphoma (HL). We focused on the volume of breast tissue exposed to radiation and the influence of gonadotoxic chemotherapy (CT). We performed a cohort study among 1,122 female 5-year survivors treated for HL before the age of 51 years between 1965 and 1995. We compared the incidence of BC with that in the general population. To assess the risk according to radiation volume and hormone factors, we performed multivariate Cox regression analyses. After a median follow-up of 17.8 years, 120 women developed BC (standardized incidence ratio [SIR], 5.6; 95% CI, 4.6 to 6.8), absolute excess risk 57 per 10,000 patients per year. The overall cumulative incidence 30 years after treatment was 19% (95% CI, 16% to 23%); for those treated before age 21 years, it was 26% (95% CI, 19% to 33%). The relative risk remained high after prolonged follow-up (> 30 years after treatment: SIR, 9.5; 95% CI, 4.9 to 16.6). Mantle field irradiation (involving the axillary, mediastinal, and neck nodes) was associated with a 2.7-fold increased risk (95% CI, 1.1 to 6.9) compared with similarly dosed (36 to 44 Gy) mediastinal irradiation alone. Women with >or= 20 years of intact ovarian function after radiotherapy at young ages (< 31 years) experienced significantly higher risks for BC than those with fewer than 10 years of intact ovarian function. Reduction of radiation volume appears to decrease the risk for BC after HL. In addition, shorter duration of intact ovarian function after irradiation is associated with a significant reduction of the risk for BC.