Anti-HER2 therapy with pyrotinib and trastuzumab in refractory HER2-positive metastatic colorectal cancer: A preliminary report from HER2-FUSCC-G study.

Abstract

97 Background: Dual-targeted HER2 therapy has led to a promising antitumor effect in HER2 positive metastatic colorectal cancer. The current study was aimed to evaluate the therapeutic efficacy of pyrotinib and trastuzumab in patients with HER2 positive colorectal cancer. Methods: HER2-FUSCC-G is an ongoing, open-label, non-randomised, phase 2a study. Patients in this subset were diagnosed as HER2 positive metastatic colorectal cancer refractory to standard chemotherapies. All the enrolled patients were treated with a loading dose of trastuzumab at 8 mg/kg followed by 6mg/kg once every three weeks, and oral pyrotinib at 400 mg per day until progression. ORR was set as the primary endpoint. Estimates of PFS (progression free survival) and OS (overall survival) were obtained with the Kaplan-Meier method and compared with log-rank test. Results: Between January 2020 to June 2021, 11 patients were enrolled in this study. The ORR was 45.5% in whole population, and 55.6% in RAS wild-type patients. At a median follow-up of 17.73 months, median PFS and OS were 7.80 and 14.97 months, respectively. The KRAS wild-type group of patients had prolonged survival (PFS: 9.97 vs. 7.73 months, P = 0.19; OS: 20.67 vs. 12.43 months, P = 0.021) compared with KRAS mutant group. Nine of 11 (81.8%) patients reported≥1 grade treatment-emergent adverse events (TATEs), while 4 (36.4%) patients reported grade 3/4 TATEs. Conclusions: The combination of trastuzumab and pyrotinib showed a promising anti-tumor response and prolonged long-term survival benefit in RAS wild-type and HER2 positive mCRC with acceptable tolerance. Clinical trial information: NCT04960943.