[A real world study on the relationship between drug resistance of targeted therapy and prognosis of HER-2-positive advanced breast cancer].

Objective: To explore the effect of primary and acquired resistance to anti-human epidermal growth factor receptor 2 (HER-2) on the overall survival of patients with HER-2 positive advanced breast cancer. Methods: The clinical characteristics of HER-2 positive patients with advanced breast cancer admitted to Cancer Hospital of Chinese Academy of Medical Sciences from January 1998 to December 2018 were collected, and their neoadjuvant/adjuvant and advanced three-line chemotherapy were summarized. Among them, targeted drugs for HER-2 included trastuzumab, pertuzumab, T-DM1, RC48-ADC, lapatinib, pyrotinib, allitinib, sipatinib, seratinib. Based on the duration of benefit from anti HER-2 treatment, the patients were divided into two groups: primary anti HER-2 resistance group and acquired anti HER-2 resistance group. In this study, the overall survival (OS) was used as the main end point. Kaplan-Meier analysis and Cox proportional risk regression model were used to analyze the effects of different drug resistance mechanisms on the overall survival. Results: The whole group of 284 patients were included. The median age of recurrence and metastasis was 48 years old, 155 (54.6%) were hormone receptor (HR) positive and 129 (45.4%) were HR negative, 128 cases (45.1%) were premenopausal and 156 cases (54.9%) were postmenopausal, 277 cases (97.5%) had a score of 0-1 in ECoG PS and 7 cases (2.5%) had a score of more than 2 in the first diagnosis of relapse and metastasis. There were 103 cases (36.3%) in the primary drug resistance group and 181 cases (63.7%) in the secondary drug resistance group. The median overall survival time of the two groups was 24.9 months and 40.4 months, respectively, with statistical significance (P<0.001). Conclusion: Primary resistance to HER-2 is one of the factors of poor prognosis in HER-2 positive breast cancer, and its mechanism needs to be further explored.