PD-1 inhibitor sintilimab treated patients with metastatic triple-negative breast cancer.

Purpose: Triple-negative breast cancer (TNBC) is a highly challenging subtype due to a unique tumor microenvironment. Several evidence (IMpassion130 trial and KEYNOTE-355 trial) supported the therapeutic effect of the immune checkpoint inhibitor in TNBC. However, the efficacy and safety of the PD-1 inhibitor sintilimab in breast cancer (BC) has not been well-investigated. So the real-world data on sintilimab-treated patients with metastatic BC were collected and analyzed in this study. Methods: The patients were eligible according to the requirements included: ages between 18 years and 75 years; recurrent or metastatic TNBC; measurable disease based on RECIST v1.1; no limitation on the prior systemic treatments; and ECOG performance status of 0-1. Patients received sintilimab 200 mg intravenously every 3 weeks until unacceptable toxicity or disease progression. Results: From 1 June 2019 to 1 October 2022, 40 female patients (median age, 55.5 years) with metastatic TNBC (mTNBC) were enrolled into the study. The median prior lines of systemic therapy for mTNBC was three (range, 1-8), with 60% of cases receiving at least three lines of therapy for metastatic disease. The visceral or brain metastasis was detected in 40.4% or 9.6% of patients, respectively. The median duration of response was 2.8 months (range, 0.7-21.0), and the median number of sintilimab doses administered was 4 (range, 1-30). The ORR and DCR were 22.5% and 72.5%, separately. The median PFS was 3.5 months (range, 1.4-21.0), with a 6-month PFS rate of 15.0% (6/40). The median OS was 52.5 months (range, 9.0-247.0) as of data cut-off. Common adverse effects were acceptable, and fatigue, skin rash, and pruritus were the frequent toxicity observed. Two cases of grade 3 curable adverse events were considered to be treatment-related. PD-L1-positive tumor was found in 40% cases (4/10) of mTNBC. Although statistical difference was not reached, the trend was obvious. Patients with PD-L1-positive tumor gained better treatment response, while the TMB-high carrier received more benefits of PFS and OS. Conclusion: In our study, preliminary evidence provided the anticancer activity and acceptable adverse effects of sintilimab administered every 3 weeks to pretreated patients with mTNBC. Sintilimab showed its efficacy and safety of immunotherapy for patients with advanced TNBC.