Cardiac exposures in breast cancer radiotherapy: 1950s-1990s.

PURPOSE: To estimate the doses to the heart and coronary arteries from common breast cancer radiotherapy (RT) regimens used worldwide from the 1950s to the 1990s.

METHODS AND MATERIALS: Virtual simulation and computed tomography planning were used to reconstruct the megavoltage and electron regimens. Manual planning was used for the orthovoltage and brachytherapy regimens. Several sources of variability associated with the dose estimates were assessed.

RESULTS: Breast or chest wall RT resulted in whole heart doses of 0.9-14 Gy for left-sided and of 0.4-6 Gy for right-sided irradiation. Internal mammary chain RT delivered heart doses of 3-17 Gy and 2-10 Gy for left- and right-sided irradiation, respectively. For most regimens, the dose to the left anterior descending coronary artery was greater than the heart dose. Scar boost, supraclavicular fossa, and axillary RT delivered mean cardiac doses of <or=3 Gy. The greatest source of variability in estimating dose from a given regimen was patient anatomy.

CONCLUSION: For most techniques, the greatest radiation doses were received by the anterior part of the heart and the left anterior descending coronary artery, a common site of atherosclerosis causing myocardial infarction. Irradiation of these structures might have contributed to the excess risk of death from heart disease seen after some past breast cancer RT regimens.