The incidence figures for secondary breast cancer are based on long-term observation of 590 female patients in the German–Austrian pediatric treatment trials dating back to the years 1978 to 1995. The authors estimate that 19% of the girls treated with radiotherapy for Hodgkin's disease develop secondary breast cancer within 30 years as a result of that therapy. Because of these findings, a structured screening program for breast cancer in this high-risk group has been set up in Germany, making use of existing structures put in place by the German Consortium for Hereditary Breast and Ovarian Cancer (Deutsches Konsortium für familiären Brust- und Eierstockkrebs).
The study authors recommend that, when supradiaphragmatic radiotherapy is necessary in girls over the age of 9, the part(s) of the chest exposed to the radiation should be kept as small as medically justifiable. This will allow the risk of breast cancer to be kept as low as possible.
Schellong et al., (2014). Breast cancer in young women after treatment for Hodgkin’s Disease during childhood or adolescence. Dtsch. Arztebl. Int., 111:3–9 [pdf]