Real-world analysis of inetetamab combined with pyrotinib plus chemotherapy for the treatment of HER2-positive advanced breast cancer: A multi-center retrospective study.

e13012 Background: Inetetamab combined with tyrosine kinase inhibitors exhibited stronger antitumor effects than inetetamab alone. At present, there was few studies on the efficacy and safety of inetetamab combined with pyrotinib in the treatment of advanced breast cancer (ABC) patients. The study aims to investigate the efficacy and safety of inetetamab combined with pyrotinib plus chemotherapy for HER2-positive ABC patients. Methods: We retrospectively investigated the medical records of eligible women who aged 18 years or older with pathologically confirmed HER2-positive recurrent or metastatic invasive breast cancer, and received at least two cycles of inetetamab combined with pyrotinib plus chemotherapy treatment regimens in multicenters in China between July 2020 and December 2022. The primary endpoint was progression-free survival (PFS) estimated by the Kaplan-Meier method. The secondary endpoints were the objective response rate (ORR), disease control rate (DCR), and safety. Cox regression model was used to identify predictive factors for PFS. Results: A total of 99 patients were included. Overall patient's median PFS was 12.3 (95% CI: 10.9-13.6) months. Of 99 evaluable patients, 53 (53.5%) patients achieved objective response, including 9 (9.1%) complete response and 44 (44.4%) partial response. The remaining 45 patients achieved stable disease as the best response, thus, the DCR was 99.0%. Patients who received Inetetamab combined with pyrotinib plus chemotherapy as first-line treatment (15.0 months 95% CI: 13.6-15.8) provided longer median PFS than that as second-line treatment (10.3 months 95% CI:9.6-10.9, p<0.001). Furtherly, the Cox multivariate regression analysis indicated that patients who received inetetamab combined with pyrotinib plus albumin-bound paclitaxel for first-line treatment achieved longer median PFS. Grade 1-2 diarrhea (59.6%), vomiting (29.3%) and nausea (28.3%), hand-foot syndrome (23.2%) were the top four most common adverse events (AEs). The most common grade ≥3 AEs were leukopenia (19.2%), diarrhea (18.2%), myelosuppression (7.1%) and neutromenia (4.0%). Conclusions: The first-line treatment of inetetamab combined with pyrotinib plus chemotherapy was an effective and safe treatment for HER2-positive ABC patients. Inetetamab combined with pyrotinib plus albumin-bound paclitaxel might be the most effective combination therapies. All AEs were controllable and tolerable.