Beyond CTS5 score: A novel nomogram predicting long-term prognosis in patients with hormone receptor-positive and human epidermal growth factor receptor 2-positive breast cancer

Background: HR+/HER2+ breast cancer are exposed to high late-recurrence risk. CTS5 is widely used in predicting late recurrence of HR+/HER2- patients. This study aims to explore the application of CTS5 in HR+/HER2+ patients and develop a novel model with greater predictive efficacy. Methods: We collect 26605 HR+/HER2+ breast cancer patients diagnosed between 2010 and 2019 from SEER database. The main survival outcome was breast cancer-specific survival (BCSS) after 5 years of diagnosis. CTS5 score was calculated. Survival analysis was performed. Cox regression identified significant clinicopathological parameters, which were used to construct a nomogram. Results: Patients were stratified into CTS5 low- (n = 10,217, 38.4%), intermediate- (n = 9,257, 34.8%) and high-risk (n = 7,131, 26.8%) groups. Patients in CTS5 high-risk subgroup were more likely to be older at diagnosis, postmenopausal and have tumors with higher TN stage and grades (all p < 0.001). High-risk patients showed worse BCSS compared with intermediate- and low-risk patients (cumulative hazard: BCSS, 7.4%, 3.2% and 1.7%, p < 0.001). Cox regression suggested age, TN stage, chemotherapy and radiotherapy were BCSS associated (all p < 0.001) while grade wasn't. A nomogram based on age, tumor size and lymph nodes was constructed. The AUC values of the ROC curves for 6, 8, and 10-year BCSS were 0.687, 0.698, and 0.700. The nomogram demonstrated a significantly higher likelihood ratio statistic compared to CTS5 (518.9 vs. 483.8, p < 0.001). Conclusions: We confirmed the prognostic value of CTS5 in HR+/HER2+ breast cancer and developed a new nomogram with superior predictive performance for long-term prognosis compared to CTS5.