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Cardiomyopathy is a known complication of anthracycline-based adjuvant chemotherapy and is more commonly reported in population-based studies of breast cancer survivors than in clinical trials. This study prospectively evaluated the prevalence of elevated cardiac biomarkers in unselected patients who had been treated with doxorubicin for early-stage breast cancer and the prevalence of reduced LVEF in patients with an elevated biomarker. All participants underwent an examination, symptom inventory, medical record review, and biomarker analysis for BNP, troponin, and plasma and urine NT-proBNP. Patients who had one or more elevated biomarkers were referred for echocardiogram; systolic dysfunction was defined as LVEF less than 55 %. Multivariable logistic regression was used to determine the associations between age, BMI, cumulative dose of doxorubicin, diabetes, hypertension, and left-sided radiation therapy and the risk of reduced LVEF. Among the 269 patients who underwent lab testing (mean age 56 years, mean time since completion of doxorubicin-based chemotherapy 6 years), 192 (72 %) had one or more elevated biomarker. Among the 166 patients who completed an echocardiogram, 11.5 % had a LVEF < 55 %. After adjusting for covariates known to affect cardiac function, multivariable logistic regression revealed plasma NT-proBNP to be the only measured cardiac biomarker associated with systolic dysfunction. There is a relationship between NT-proBNP and the frequency of reduced LVEF in women treated with doxorubicin for curative intent; further study of NT-proBNP as a potential biomarker for subclinical cardiac dysfunction after exposure to anthracyclines is warranted.