Even the presence of minimal changes in regional wall motion abnormalities with exercise stress echocardiography predicts MACE and all-cause mortality in patients with previous chest radiotherapy

Abstract Background Exercise stress echocardiography (ESE) is a non-invasive, radiation-free, and widely available technique that has demonstrated a reliable accuracy for the detection of coronary artery disease (CAD). Chest radiotherapy (RT) is associated with accelerated age-related atherosclerosis and fibrosis in a dose-dependent manner. ESE plays a role as a screening tool of RT induced heart disease, however, the prognostic value of changes in regional wall motion abnormalities in this population during ESE has not been evaluated. Methods This is a retrospective cohort study of breast cancer survivors treated with adjuvant RT that underwent ESE from 2000-2020 after treatment completion. Outcomes evaluated were: major adverse cardiovascular events (MACE: cardiovascular death, myocardial infarction, revascularization and stroke); and all-cause mortality. A univariate analysis was performed to characterize the population. Continuous variables were presented as means ± standard deviation (SD) or median with quartile 1 and 3 (Q1, Q3), and categorical variables as numbers and percentages. A Cox regression model adjusted by age and cardiovascular risk factors was used to evaluate variables associated with outcomes, and a time to first event approach was used. A p-value of <0.05 was considered statistically significant. Results From 2000-2020, 507 patients, with a mean age 66 ± 10 years, underwent ESE at a median of 5.8 years after RT completion. The most prevalent comorbidities were dyslipidemia (59%), HTN (55%) and obesity (37%). 55% underwent RT for left-sided breast cancer and 45% for right-sided, and median RT dose was 6000 cGy. Baseline characteristics are presented in Table 1. Most patients underwent Bruce Protocol (92%). Patients exercised a mean time of 6.6 minutes achieving 7.3 METS and 109% of functional aerobic capacity (Table 2). At a median follow up of 7.8 years, 61 MACE events occurred. Predictors of MACE were double product, baseline and stress EF, baseline and peak regional wall motion abnormalities (RWMA), development of new ischemic RWMA, inability to reach 85% of maximum HR, and an abnormal EF response with stress after adjusting for age, HTN, DM, smoking history, dyslipidemia, obesity, prior MI and cancer staging (Fig 1). Predictors of all-cause mortality were METS, LV mass index, baseline and peak RWMA, development of new ischemic RWMA and an abnormal EF change with stress even after adjusting for variables described previously (Fig 2). Conclusions The development of new or worsening RWMA of just 2 segments with stress, was a significant predictor of MACE and all-cause mortality in a large cohort of breast cancer survivors undergoing multidisciplinary management including adjuvant RT. Special emphasis on management of cardiovascular comorbidities and closer surveillance are recommended for these patients.