Morbidity and mortality of ischaemic heart disease in high-risk breast-cancer patients after adjuvant postmastectomy systemic treatment with or without radiotherapy: analysis of DBCG 82b and 82c randomised trials. Radiotherapy Committee of the Danish Breast Cancer Cooperative Group.

BACKGROUND: Radiotherapy in addition to systemic treatment after mastectomy prolongs survival in high-risk breast-cancer patients. However, adjuvant radiotherapy has a potential association with ischaemic heart disease. We assessed morbidity and mortality from ischaemic heart disease in patients treated with postmastectomy radiotherapy.

METHODS: Between 1982 and 1990, we randomly assigned 3083 women at high risk of breast cancer, after mastectomy, adjuvant systemic treatment with (n=1538) or without (n=1545) radiotherapy. An anterior photon field was used against the periclavicular region and the axilla. The chest wall was treated through two anterior shaped electron fields, one including the internal mammary nodes. The intended dose was 48-50 Gy in 22-25 fractions, at four to five fractions per week. We obtained information on morbidity and mortality of ischaemic heart disease over a median of 10 years. Analysis was by intention to treat.

FINDINGS: More women in the no-radiotherapy group than in the radiotherapy group died of breast cancer (799 [52.5%] vs 674 [44.2%]), whereas similar proportions of each group died from ischaemic heart disease (13 [0.9%] vs 12 [0.8%]). The relative hazard of morbidity from ischaemic heart disease among patients in the radiotherapy compared with the no-radiotherapy group was 0.86 (95% CI 0.6-1.3), and that for death from ischaemic heart disease was 0.84 (0.4-1.8). The hazard rate of morbidity from ischaemic heart disease in the radiotherapy group compared with the no-radiotherapy group did not increase with time from treatment.

INTERPRETATION: Postmastectomy radiotherapy with this regimen does not increase the actuarial risk of ischaemic heart disease after 12 years.