Adjuvant chemotherapy guidance for pT1–3N0–1 breast cancer patients with HR(+), HER2(−) subtype: a cohort study based on the SEER database

BACKGROUND: Although the results of gene testing can guide early breast cancer patients with hormone receptor (HR)(+), human epidermal growth factor receptor 2 (HER2)(−) to decide whether they need chemotherapy (CHT), there are still many patients worldwide whose problems cannot be resolved by genetic testing. METHODS: A total of 144,735 patients with HR(+), HER2(−), pT1–3N0–1 breast cancer from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015 were included. They were divided into CHT and no CHT groups, and after propensity score matching (PSM), overall survival (OS) and breast cancer-specific survival (BCSS) were tested using the Kaplan-Meier plot. The Cox proportional hazards regression model was used to identify independent prognostic factors. A nomogram was constructed to score each patient. Patients were divided into high- or low-risk groups according to their nomogram score using X-tile. RESULTS: Patients receiving CHT had better OS before and after matching (P<0.05), but BCSS was not significantly different between patients with and without CHT after matching. Independent prognostic factors were included to construct the nomogram, which could calculate the risk score for each patient, and then all patients were divided into two groups using X-tile: a risk score ≤238 was classified as the low-risk group and >238 was classified as the high-risk group. Patients in the high-risk group (score >238) could achieve better OS and from CHT; however, the low-risk group (score ≤238) could not. CONCLUSIONS: In this study, a well-validated nomogram and a risk stratification model was built. Patients in the high-risk group should receive CHT, while patients in low-risk group may be exempt from CHT.