Shen K, Yao L, Wei J, et al. - Using a large population-based cohort, researchers sought to find out prognostic factors in bilateral primary breast cancer (BPBC) by competing risk analysis. From the Surveillance, Epidemiology, and End Results Database, female patients diagnosed with BPBC between 2004 and 2014 were randomly divided into training (n = 7,740) and validation (n = 2,579) cohorts. Independent prognostic factors in both multivariate Cox hazard regression analysis and competing risk analysis were age, interval time, lymph nodes invasion, tumor size, tumor grade and estrogen receptor status. The calibration curves demonstrated a high concordance between the nomogram prediction and actual observation. According to findings, BPBC's prognosis was based on bilateral tumors. The worse characteristics model's competing risk nomogram can help clinicians predict survival in a simple and effective manner. Metachronous bilateral breast cancer had lower survival than bilateral synchronous breast cancer.