Coronary Artery Calcium Score Assessment in Breast Cancer Patients After Three-Dimensional Conformal Radiotherapy: Is Calcium Score an Appropriate Screening Study?

Background: Adjuvant radiation therapy (RT) improves the prognosis of breast cancer (BC); nevertheless, causes post-RT complications. One of the most life-threatening complications of RT in BC patients is atherosclerotic coronary artery disease (CAD). Compared with old two-dimensional RT (2D-RT), newer three-dimensional conformal radiotherapy (3D-CRT) protects normal tissues including the heart from irradiation. Early detection of plaques using coronary artery calcium score (CACS) could improve the post-RT BC survivors’ outcomes. Objectives: This study assessed CACS in BC patients who underwent 3D-CRT to find whether there is any significant difference between their CACS and those of non-BC patients. Patients and Methods: CACS of fifty BC patients with different intervals from RT - case - and fifty women with no history of BC or RT - control - using 64-slice ECG-gated CT scan were assessed as Agatston score (AS). The risk factors of CAD, the Framingham’s 10-year risk score, and the age-matched CACS percentiles were evaluated. Results: No AS difference between the case and control was found. No correlation between AS and RT-to-follow-up time interval, laterality of BC, Framingham’s 10-year risk score or traditional CAD risk factors were detected. Increase in CACS related to the senile atherosclerotic process was shown (P < 0.001). Conclusion: No significant difference in CACS was found in BC patients treated by 3D-CRT in comparison with those of non-BC individuals or BC patients who treated by 2D-RT. This finding may be the result of either the non-calcified nature of radiation-induced CAD plaques or reduced cardiac radiation in 3D-CRT, leading to myocardial microvascular disease rather than senile calcified atherosclerotic plaques. CACS may not be an appropriate screening test to detect early CAD in these patients.