Treatment patterns and clinical outcomes of chidamide combined with endocrine therapy in hormone receptor-positive, HER2-negative metastatic breast cancer: A real-world multicenter study

BACKGROUND

Chidamide is a selective histone deacetylase inhibitor approved for patients with hormone receptor (HoR)-positive and HER2-negative metastatic breast cancer (MBC). We aimed to investigate the efficacy, safety, and treatment patterns of chidamide and identify clinicopathological factors that predict the efficacy of chidamide in real-world scenarios.

METHODS

Consecutive MBC patients treated with chidamide from January 2020 to August 2021 across 11 institutions were enrolled in this multicenter, retrospective study. Eligible patients were pre- and postmenopausal women who had clinically or histologically confirmed ER-positive, HER2-negative MBC, and Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Patients with multiple primary malignancies or missing baseline characteristics were excluded. Patients received 30 mg chidamide orally twice a week, combined with aromatase inhibitors (AIs) or non-AIs. Efficacy analyses included progression-free survival (PFS), objective response rate (ORR), and clinical benefit rate (CBR). Univariate and multivariate Cox regression analyses were performed to identify the potential efficacy predictors.

RESULTS

A total of 157 patients were finally included for analysis. The median number of lines prior to chidamide was four. In the whole cohort, the median PFS was 4.2 months (95% confidence interval [CI] 3.8-4.5). The ORR was 7.5% and the CBR was 31.3%. The efficacy of chidamide was consistent in patients pretreated with CDK4/6 inhibitors and patients treated with different endocrine combinations. Multivariate analysis indicated that patients who had liver metastases (adjusted HR = 1.66, 95% CI 1.14-2.43, adjusted p = 0.008) or ≥3 prior lines of treatment (adjusted HR = 1.80, 95% CI 1.17-2.77, adjusted p = 0.008) had significantly worse PFS. The most common AEs with chidamide were thrombocytopenia, leucopenia, neutropenia, and anemia.

CONCLUSION

This study provided real-world data for the use of chidamide in patients with HoR-positive and HER2-negative MBC. Our data endorsed the use of chidamide in patients pretreated with CDK4/6 inhibitors and patients treated with different endocrine combinations.