Abstract PO2-06-11: A phase II randomized trial of gemcitabine plus cisplatin(GP) vs gemcitabine plus carboplatin (GC) as the first-line treatment for patients with metastatic triple-negative breast cancer

Abstract Background: Triple-negative breast cancer (TNBC) is an aggressive disease with limited treatment options and poor prognosis. Gemcitabine plus carboplatin (GC) is one of the classic chemotherapeutic regimens for patients with metastatic triple-negative breast cancer(mTNBC) and also a backbone regimen for chemoimmunotherapy, with a median progression-free survival (PFS) of 4.6 months in the first-line (O'Shaughnessy J, et al. J Clin Oncol 2014). Gemcitabine plus cisplatin (GP) has also demonstrated promising efficacy and safety in the first-line phase III trial of mTNBC, with a median PFS of 7.7 months (Hu XC, et al. Lancet Oncol 2015). To further investigate the superiority between carboplatin and cisplatin when combined with gemcitabine, a prospective phase II study was conducted to directly compare the efficacy and safety of GP with GC in the first-line treatment for patients with mTNBC (NCT02341911). Methods: Patients with untreated mTNBC were randomized 1:1 to receive gemcitabine (1250 mg/m2, D1,8) plus cisplatin (75 mg/m2, D1) or gemcitabine (1000mg/m2, D1,8) plus carboplatin (area under the curve 2 mg × min/mL, D1,8) every 21 days until disease progression or intolerable toxicity. The stratification factors included visceral metastasis (yes or no) and the number of metastatic sites (1, 2, or ≥3). The primary endpoint was PFS and secondary endpoints included overall response rate (ORR), overall survival (OS), and safety. Results A total of 150 mTNBC patients were enrolled. After a median follow-up of 49.1 months (IQR 31.3-70.7), PFS events had been recorded in 55 (73.3%) of 75 patients in the GP group and 59 (78.7%) of 75 patients in the GC group. PFS was numerically longer in the GP group than in the GC group, though not significantly (median, 7.8 months [95% CI 7.2–8.4] vs. 6.9 months [95% CI 6.4–7.4]; HR, 0.93; 95% CI 0.64–1.34; P = 0.689; stratified HR, 0.84; 95% CI 0.58–1.23; P = 0.375). Median OS was 20.7 months (95%CI 17.9-23.5) in GP group and 20.9 months (95%CI 15.3-26.5) in GC group, HR, 1.13; 95% CI 0.77–1.67; P = 0.537; stratified HR, 1.03; 95% CI 0.70–1.52; P = 0.886). The ORR of GP and GC was 49.3% and 41.3% in the intent-to-treat population. Dose reduction occurred in 30(40.0%) patients in the GP group and 38 (50.7%) patients in the GC group. Grade 3 and 4 hematological AEs, including leucopenia, neutropenia, anemia, and thrombocytopenia were slightly higher in the GC group. Grade 3 and 4 non-hematological AEs, including nausea, vomiting, and hearing toxicity, were more common in the GP group. No treatment-related deaths were reported. Conclusions Cisplatin was not associated with a survival advantage over carboplatin when combined with gemcitabine as a first-line treatment for patients with mTNBC, though numerically longer PFS and higher ORR was observed. The safety profiles of the two combinations were different but the adverse events were manageable. Citation Format: Chengcheng Gong, Yannan Zhao, Leiping Wang, Jun Cao, Zhonghua Tao, Ting Li, Mingchuan Zhao, Haitao Miao, Juan Jin, Xichun Hu, Biyun Wang. A phase II randomized trial of gemcitabine plus cisplatin(GP) vs gemcitabine plus carboplatin (GC) as the first-line treatment for patients with metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-06-11.