Quantitative coronary angiography findings of patients who received previous breast radiotherapy

To compare the coronary angiographic findings between patients who had previous left sided versus right sided breast cancer radiotherapy (RT).

Between 1995 and 2009, 12,696 patients who underwent curative RT for breast cancer at Princess Margaret Hospital were screened to assess if they had been investigated with a post-RT coronary angiogram. Two cardiologists, blinded to the laterality of radiation treatment, assessed all angiograms and measured the percentage of stenotic lesions, the mean diameters of each segment of the left anterior descending artery (LAD) and the right coronary artery (RCA) using quantitative coronary angiography (QCA).

Ninety-one patients were included, 49 patients with left sided RT and 42 with right sided RT. The median time from RT to coronary angiogram was 4.2 years (range: 22 days-16.9 years). Seventeen patients (35%) in the left sided RT group and 17 (40%) in the right sided RT group needed coronary revascularization (percutaneous coronary intervention or by-pass surgery). The LAD territory was revascularized in 12 (24%) and 11 (26%) patients, respectively. The proportion of clinically significant stenoses, degree of stenoses and mean vessel diameter were not significantly different between the two groups. In 33 patients who had coronary angiograms >5 years after breast RT (17 left-sided and 16 right-sided), the only statistically significant finding was marginally narrower mid RCA segments among those who had right sided RT: 2.52 mm versus 2.92 mm (P=0.039).

In our patients, left sided breast cancer RT did not increase the risk of coronary artery disease within the first few years, when compared to right sided RT. However, with the limitation of short duration between radiotherapy and coronary angiogram, late development of coronary artery stenoses 10-15 years after left sided RT could not be excluded.