Coronary artery calcification severity in long term breast cancer survivors treated with isolated contemporary radiotherapy: Relation to dose and CV risk factors.

Background: Ancillary breast cancer (BC) radiation therapy (RT), particularly associated with chemotherapy, increases the risk of coronary artery disease (CAD). However, it remains unclear whether this risk also applies to isolated contemporary radiotherapy without chemotherapy.

Methods: Seventy-five BC patients (35 left-sided and 40 right-sided) treated with RT and available dosimetry, prospectively underwent Agatston calcium score (CAC) and coronary CT angiography (CTCA) a median of 11 ± 1 years later and were compared to 75 age- and cardiovascular (CV) risk factor-matched female controls without a history of cancer.

Results: BC patients and controls had similar ages (62 ± 7 vs. 61 ± 7 years, p = 0.63), CV risk factors and estimated Score2/OP risk (3.8 % IQR 2.6-6 vs. 3.3 % IQR 2.3-5.4, p = 0.52). CAC scores (0 IQR 0-79 vs. 0 IQR 0-34, p = 0.62) and age-predicted percentile CAC scores (p = 0.61) were similar between BC patients and controls, with no significant difference between left- and right-sided RT. Multivariable analysis revealed that CAC scores in BC patients were predicted only by a family history of CAD and by Score-2/OP risk, but not by cardiac radiation exposure. By CTCA 68 % of BC patients had no or very mild coronary disease, and only 14 % had more than moderate stenosis (>50 %), which was predicted by CAC scores > 79 (AUC = 0.97).

Conclusion: Eleven years post-treatment with isolated contemporary RT for BC, patients exhibited similar CAC severity as age- and risk factor-matched controls. CAC was associated only with CV risk factors, but not radiation dose, suggesting contemporary RT for BC is not linked to higher subclinical CAD prevalence.