Multiple primary tumours in patients treated with radiotherapy for breast cancer.

Between January 1954 and March 1964, 3926 patients with primary breast cancer were referred to The Department of Clinical Oncology, Edinburgh. One hundred and eighty patients developed 195 malignancies subsequent to the treatment of their initial breast cancer. Overall, the total number of second tumours was not significantly in excess of the expected incidence in the general population. However, statistical analysis revealed a significant increase in the incidence of rectal, skin and bone tumours. The excess of bone tumours was likely due to radiation exposure. There was not an overall excess of tumours within the irradiated or scattered radiation volume.