Coronary artery findings after left-sided compared with right-sided radiation treatment for early-stage breast cancer

To compare the incidence and distribution of coronary artery disease after left-sided versus right-sided irradiation in patients treated with breast conservation for early-stage breast cancer who subsequently underwent cardiac stress testing and/or catheterization for cardiovascular symptoms.

The medical records of 961 stage I-II breast cancer patients treated from 1977 to 1995 at the University of Pennsylvania with conventional tangential beam radiation treatment (RT) were screened for cardiac stress tests and catheterizations performed after RT. The results of these tests were analyzed by laterality of RT and compared with baseline cardiovascular risk.

At diagnosis, patients with left-sided and right-sided breast cancer had the same estimated 10-year risk (both 7%) of developing coronary artery disease. At a median time of 12 years post-RT (range, 2 to 24 years), 46 patients with left-sided and 36 patients with right-sided breast cancer (total, N = 82) had undergone cardiac stress testing. A statistically significant higher prevalence of stress test abnormalities was found among left (27 of 46; 59%) versus right-side irradiated patients (three of 36; 8%; P = .001). Furthermore, 19 of 27 of left-sided abnormalities (70%) were in the left anterior descending artery territory. Thirteen left-side irradiated patients also underwent cardiac catheterization revealing 12 of 13 with coronary stenoses (92%) and eight of 13 with coronary stenoses (62%) solely in the left anterior descending artery.

Patients treated with left-sided radiation as a component of breast conservation have an increased risk of late, radiation-associated coronary damage. Treatment with modern radiation techniques may reduce the risk of cardiac injury.