Distribution of coronary artery stenosis after radiation for breast cancer

To study distribution of coronary artery stenosis among patients with breast cancer (BC) and to assess correlation between radiotherapy (RT) and location of stenosis.

A Swedish BC cohort diagnosed from 1970 to 2003 was linked to registers of coronary angiography from 1990 to 2004, which yielded 199 patients. Stenoses of the coronary arteries were graded from 0 to 5, where 0 indicated a normal vessel and 5 indicated occlusion. Two hotspot areas for radiation were defined: proximal right coronary artery (prox RCA), mid and distal left anterior descending artery and distal diagonal (mdLAD + dD). RT regimens were categorized as high or low risk of irradiating the hotspot areas. Left breast/chest wall was considered high risk for mdLAD + dD; left internal mammary chain (IMC), high risk for prox RCA and mdLAD + dD from 1970 to 1995 and thereafter solely for mdLAD + dD; and right IMC, high risk for prox RCA. Other RT targets and no RT were considered low risk. Results were expressed in odds ratios (ORs) and 95% CIs.

For irradiated left- versus right-sided BC, the OR for grade 3 to 5 stenosis in mdLAD + dD was 4.38 (95% CI, 1.64 to 11.7), and for grade 4 to 5 stenosis, the OR was 7.22 (95% CI, 1.64 to 31.8). For high-risk RT versus low-risk or no RT, the OR for grade 3 to 5 stenosis in hotspot areas was 1.90 (95% CI, 1.11 to 3.24).

An increase of stenosis in mdLAD + dD in irradiated left-sided BC and an association between high-risk RT and stenosis in hotspot areas for radiation indicate a direct link between radiation and location of coronary stenoses.