Abstract Background: Anthracycline (AC) and/or trastuzumab (T) are the most commonly used for neo-/adjuvant therapy for early breast cancer. However, use of those regimens are limited owing to congestive heart failure (CHF). Although reported incidence from pivotal trials is very low and acceptable, no big data-based population study has not been conducted in Koreans yet. The aim of this study was to analyze the incidence, time to occurrence, and risk factors for CHF in patients with early breast cancer, who were treated with AC and/or T therapy, in Korea. Methods: We used the Health Insurance Review and Assessment Service database and included women with no prior history of CHF who were aged >19 years and diagnosed as having early breast cancer between 2007 and 2016. Only patients who had received breast cancer surgery and AC and/or T therapy were included. Patients with metastatic cancer codes were excluded. Result: In total, 86,086 patients were included for this analysis. The incidence and median time to occurrence of CHF according to chemotherapy type were, 3.27% and 683.5 days in the AC only group, 6.39% and 374 days in the AC followed by T group, and 4.43% and 286 days in the T with or without non-AC group, respectively. The multivariate Cox regression analysis revealed that the adjusted hazard ratio (HR) for CHF was increased with older age; in those aged ≥65 years versus <50 years (HR, 2.79; 95% confidence interval [CI], 2.50–3.12). The HR in the AC followed by T group was significantly higher than that in the AC only group (HR, 2.21; 95% CI, 2.05-2.37). The T with or without non-AC group also showed a significantly higher HR than the AC only group (HR, 1.67; 95% CI, 1.37-2.04). CCI scores of ≥2 were significant predictors of CHF; score 2 versus 0 (HR, 1.30; 95% CI, 1.18-1.45), and score ≥3 versus 0 (HR, 1.87; 95% CI, 1.69-2.06). In addition, preexisting medical conditions were significant predictors for CHF: hypertension (HR, 1.58; 95% CI, 1.45-1.72), diabetes (HR, 1.17; 95% CI, 1.07-1.28), and ischemic heart disease (HR, 1.60; 95% CI, 1.45-1.76). Conclusion: This is the first big data-based population study in Korea on the development of CHF after treatment with AC and/or T. The overall incidence of CHF was 3% to 6%, with a median time to occurrence of 1 to 2 years. Adjusted HR increased with older age, AC followed by T therapy, CCI scores ≥2, and preexisting conditions. Table 1. Incidence and median time to occurrence of congestive heart failure according to chemotherapy typeChemotherapy typeTotalCHF event (%)Median time to occurenceAC only66,6992,182 (3.27%)683.5AC followed by T17,0621,090 (6.39%)374T ± non-AC2,325103 (4.43%)286 Table 2. Cox proportional hazards model for congestive heart failure, adjusted for age, chemotherapy type, and Charlson comorbidity index scoreVariableP-valueHR95% CIAge (ref <50 years) 50-64 years<0.00011.541.43-1.66≥65 years<0.00012.792.50-3.12Chemotherapy type (ref AC only) AC folloewed by T<0.00012.212.05-2.37T ± non-AC<0.00011.671.37-2.04Charlson comorbidity index score (ref 0) 10.12061.080.98-1.192<0.00011.301.18-1.45≥3<0.00011.871.69-2.06 Citation Format: Choi JY, Cho EY, Lee JW, Kim JW, Choi YJ, You JY, Bae SY, Jung SP, Cho KR, Park KH. Incidence and risk factors for congestive heart failure in early breast cancer received anthracycline and/or trastuzumab; big-data analysis of Korean health insurance review and assessment service database [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-08-09.