Background: Female Hodgkin lymphoma (HL) survivors treated with chest radiotherapy (RT) at a young age have a strongly increased risk of breast cancer (BC). Recently concern has been raised that anthracyclines may also increase BC risk, based on studies in childhood cancer survivors with/without a history of chest RT. So far, the association between anthracyclines and BC risk has not been examined in cancer survivors treated at adolescent/adult ages. Now that RT dose and volumes are decreasing, the potential contribution of anthracyclines to BC risk is an important issue. Methods: We assessed BC risk in a cohort of 2314 female 5-year HL survivors, treated at ages 15-50 years and diagnosed between 1965 and 2008 in 20 Dutch hospitals. Treatment factors were time-dependently included in the analysis, focusing on the effect of anthracycline exposure on BC risk. Results: After a median follow-up of 18.8 years, 258 women developed invasive BC or ductal carcinoma in situ as a subsequent malignancy. The 30-year cumulative incidence was 15.0% (95% Confidence Interval (CI) 12.8-17.4%). Mantle field RT (or other RT involving both axillae) was associated with increased risk of BC (Hazard ratio (HR) 1.9; 95% CI 1.2-2.8) compared to no supradiaphragmatic RT or RT to the neck only (Table 1). Gonadotoxic treatment (>4.2 g/m² procarbazine or pelvic RT) significantly decreased this risk. In a multivariable analysis, anthracycline exposure was associated with increased BC risk (HR 1.8; 95% CI 1.3-2.5) in patients who received a cumulative dose of >200 mg/m². Among patients exposed to gonadotoxic treatment, the HR of BC associated with >200mg/m² anthracyclines was 3.8 (95% CI 2.0-7.2), with a trend for higher risk with higher anthracycline dose (HR 1.58 per 100mg/m² anthracycline, p<0.001). Conclusions: Our results suggest an association of anthracyclines with BC risk in HL survivors. Also when accounting for the protective effect of gonadotoxic treatment on RT-associated BC risk, anthracyclines significantly contributed to a higher BC risk.

RT: radiotherapy; adjusted for age at first treatment.