[Effects of adjuvant trastuzumab on long-term survival of T1N0M0 stage human epidermal growth factor receptor 2 positive breast cancer: a real-world study].

Objective: To investigate the prognosis impact of adjuvant trastuzumab treatment on human epidermal growth factor receptor 2 (HER-2) positive early breast cancer patients. Methods: A retrospective study was conducted, HER-2-positive T1N0M0 stage breast cancer patients who underwent surgery in the Affiliated Tumor Hospital of Xinjiang Medical University from January 2010 to December 2019 were divided into treatment group and control group according to whether they were treated with trastuzumab or not. Propensity score matching (PSM) was used to balance the confounding bias caused by differences in baseline characteristics between the two groups. Cox proportional hazards model was used to analyze the risk factors affecting disease-free survival (DFS). The Kaplan-Meier method was used to estimate the 3- and 5-year DFS and overall survival (OS) rates of the two groups before and after PSM. Results: There were 291 patients with HER-2 positive T1N0M0 stage breast cancer, including 21 cases in T1a (7.2%), 61 cases in T1b (21.0%), and 209 cases in T1c (71.8%). Before PSM, there were 132 cases in the treatment group and 159 cases in the control group, the 5-year DFS rate was 88.5%, and the 5-year OS rate was 91.5%. After PSM, there were 103 cases in the treatment group and 103 cases in the control group, the 5-year DFS rate was 86.0%, and the 5-year OS rate was 88.5%. Before PSM, there were significant differences in tumor size, histological grade, vascular invasion, Ki-67 index, postoperative chemotherapy or not and radiotherapy between the treatment group and the control group (P<0.05). After PSM, there were no significant difference in clinicopathological features between the treatment group and the control group (P>0.05). Multivariate analysis showed that histological grade (HR=2.927, 95 CI: 1.476, 5.805; P=0.002), vascular invasion (HR=3.410, 95 CI: 1.170, 9.940; P=0.025), menstrual status (HR=3.692, 95 CI: 1.021, 13.344, P=0.046), and chemotherapy (HR=0.238, 95 CI: 0.079, 0.720; P=0.011) were independent factors affecting DFS. After PSM, the 5-year DFS rate of the treatment group was 89.2%, while that of the control group was 83.5%(P=0.237). The 5-year OS rate of the treatment group was 96.1%, while that of the control group was 84.7%(P=0.036). Conclusion: Postoperative targeted therapy with trastuzumab can reduce the risk of recurrence and metastasis in patients with HER-2-positive T1N0M0 stage breast cancer.