CORONARY ARTERY CALCIFICATION AS A PERSONALIZED MARKER FOR CARDIAC EVENTS IN BREAST CANCER PATIENTS

Abstract

Breast cancer patients are at high risk for cardiac events. This is attributed to three factors: cardiotoxic chemo and radiotherapy, increased prevalence of cardiovascular risk factors and less stringent physician prescribing of primary prevention. As such, this population could benefit from more rigorous cardiovascular risk assessment. In the general population, coronary artery calcification (CAC) is a strong and independent marker of CAD. When present it can be readily identified on routine CT chest studies. Since breast cancer patients frequently undergo thoracic CT studies as part of cancer staging, or complication assessment, it affords the opportunity to detect CAC. In this study, we evaluate the impact of CAC in risk stratification of the breast cancer population. In this retrospective analysis, we recruited 408 breast cancer patients referred to the Ottawa Hospital Cardiac Oncology Clinic between January 2008 and June 2017. Patients with prior non-gated thoracic CT studies were reviewed and patients with a prior cardiac event were excluded. The major adverse cardiac events (MACE) end points of this study included total mortality, new heart failure, coronary revascularization, new onset atrial fibrillation. Statistical analysis of the data was performed using SPSS. The association between cardiac events was assessed using univariable, multivariable and survival analysis. On univariable analysis CAC (p<0.001) and Framingham Risk Score (p<0.001) were significant associated with MACE and were adjusted for in subsequent models. In multivariable analysis CAC predicted MACE with an adjusted odds ratio of 1.45 (p=0.003). Similarly in survival free analysis CAC produced a HR of 3.85 (p=0.005, 95%CI = 1.51-9.82). Subgroup analysis demonstrated that the presence of CAC was independently associated with revascularization (p=0.0098) and heart failure (p=0.0078). The Net Reclassification Index (NRI) was used to compare the incremental effectiveness of Framingham and CAC compared to the Framingham risk score alone. The NRI was 0.1658. By reclassifying patients incrementally with CAC, we found that 16.4% of our population could benefit from alterations in their statin therapy. Specifically, therapy could be optimized in 40.0% of high-risk patients and 13.8% of low-risk patients. In a breast cancer population attending a cardiac oncology clinic the presence of CAC was strongly associated with cardiac events. These findings suggest that it may be possible to improve risk stratification using CAC as a personalized marker of risk.