Pyrotinib or lapatinib plus capecitabine for HER2+ metastatic breast cancer (PHOEBE): A randomized phase III trial.
Binghe Xu, Min Yan, Fei Ma, Xichun Hu, J. Feng, Quchang Ouyang, Zhongsheng Tong, Huiping Li, Qingyuan Zhang, Tao Sun, Xian Wang, Yongmei Yin, Ying Cheng, Wěi Li, Xiaoyu Zhu, Chunxia Chen, Jianjun Zou, The PHOEBE Group
Abstract
1003 Background: Pyrotinib (an irreversible pan-ErbB inhibitor) plus capecitabine showed clinically meaningful benefits and acceptable tolerability in patients (pts) with HER2+ metastatic breast cancer (MBC) in phase 1 and 2 studies. Methods: This open-label, multicenter, randomized phase 3 study enrolled HER2+ MBC pts after trastuzumab and taxanes, and/or anthracyclines. Up to two prior lines of chemotherapy (chemo) for metastatic disease were allowed. Pts were randomly assigned (1:1) to receive pyrotinib 400 mg or lapatinib 1250 mg qd continuously plus capecitabine 1000 mg/m 2 bid on days 1–14 of 21-day cycles. The primary endpoint was progression-free survival (PFS) per blinded independent central review. Results: From Jul 2017 to Oct 2018, 267 pts were randomized to the pyrotinib (n=134) or lapatinib (n=133) arm. One pt in the lapatinib arm did not receive study treatment and was excluded from analyses. 42.5% and 34.8% of pts in the pyrotinib and lapatinib arm had no prior chemo for metastatic disease, 41.8% and 49.2% had one prior line, and 15.7% and 15.9% had two lines. At the planned interim analysis, the median PFS was 12.5 months (95% CI 9.7–not reached) with pyrotinib plus capecitabine vs 6.8 months (95% CI 5.4–8.1) with lapatinib plus capecitabine (HR 0.39 [95% CI 0.27–0.56]; P<0.0001), which met the criterion for statistical significance (≤0.0066). Among trastuzumab-resistant pts, prolonged PFS with pyrotinib plus capecitabine was also observed (12.5 months [95% CI 6.9 to not reached] vs 6.9 months [95% CI 5.4 to not reached]; HR 0.60 [95% CI 0.29 to 1.21]). Benefits in objective response rate, clinical benefit rate, and duration of response with pyrotinib plus capecitabine were also indicated (Table). The most common grade ≥3 adverse events were diarrhea (30.6% vs 8.3% in the pyrotinib vs lapatinib arm) and hand-foot syndrome (16.4% vs 15.2%). Conclusions: In pts with HER2+ MBC after trastuzumab and chemo, pyrotinib plus capecitabine achieved a significant better PFS than lapatinib plus capecitabine, with manageable toxicity, verifying the phase 2 findings. Clinical trial information: NCT03080805 . [Table: see text]