Angiosarcoma after radiotherapy: a cohort study of 332,163 Finnish cancer patients.

We evaluated the risk of angiosarcoma after radiotherapy among all patients with cancers of breast, cervix uteri, corpus uteri, lung, ovary, prostate, or rectum, and lymphoma diagnosed in Finland during 1953-2003, identified from the Finnish Cancer Registry. Only angiosarcomas of the trunk were considered, this being the target of radiotherapy for the first cancer. In the follow-up of 1.8 million person-years at risk, 19 angiosarcomas developed, all after breast and gynaecological cancer. Excess of angiosarcomas over national incidence rates were observed after radiotherapy without chemotherapy (standardised incidence ratio (SIR) 6.0, 95% confidence interval (CI) 2.7-11), after both radiotherapy and chemotherapy (SIR 100, 95% CI 12-360), and after other treatments (SIR 3.6, 95% CI 1.6-7.1). In the regression analysis however, the adjusted rate ratio for radiotherapy was 1.0 (95% CI 0.23-4.4). Although an increased risk of angiosarcoma among cancer patients is evident, especially with breast and gynaecological cancer, the excess does not appear to be strongly related to radiotherapy.