Combination of avelumab, trastuzumab and mFOLFOX6 demonstrates clinical activity in metastatic gastroesophageal adenocarcinoma with HER2 amplification

Trastuzumab is a monoclonal antibody directed to HER2, indicated in combination with chemotherapy in 20 to 30% metastatic esophageal or gastric adenocarcinomas that overexpress HER2. However, the addition of the triple combination involving chemotherapy, anti-HER2 therapy, and immunotherapy still lacks evidence  

Among the subjects presented during the American Association for Cancer Research (AACR) Annual Meeting 2021 is the HCRN GI17-319 (NCT03783936), a prospective, open-label, single-arm, multicenter, phase II clinical trial that evaluated the efficacy of mFOLFOX6 + trastuzumab + avelumab in the first line of treatment in patients with metastatic gastroesophageal adenocarcinoma with HER2 amplification.  

The main objective of this trial is to estimate the best objective response rate in these patients within 24 weeks by RECIST 1.1 criteria. Secondary objectives include estimating progression-free survival (PFS) by both RECIST1.1 and iRECIST criteria, overall survival (OS), 24-week disease control rate (DCR) by RECIST1.1, and iRECIST, and characterizing the safety data associated with the regime.  

Participants received nine cycles of induction avelumab, trastuzumab and mFOLFOX6 every 14 days, followed by maintenance avelumab + trastuzumab every 14 days. 

 Findings 

 A total of 18 individuals, including the safety test of six participants, were enrolled. The response rate at 24 weeks was 61% (95% CI: 39-84%), including a complete response. The confirmed overall response rate was 39%, but three unconfirmed participants are still under treatment.   

Along 11 progression events, the median PFS was 8.0 months (95% CI: 4.2-11.9). The regimen was well tolerated, with the most common treatment-related grade 3-4 adverse events: neutropenia (28%), thrombocytopenia (11%), anemia (11%), and hypokalemia (11%). 

 Researchers concluded that the combination of avelumab, trastuzumab, and mFOLFOX6 demonstrated favorable clinical activity, response rate, and median PFS, especially when compared to the expected results with trastuzumab + chemotherapy from historical basis. These results corroborate the findings of previous minor studies involving chemotherapy, trastuzumab, and immune coreceptor inhibitors in patients with metastatic gastroesophageal adenocarcinoma with HER2 amplification. 

 References:  

1. Lee MS, et al. Phase II study of avelumab and trastuzumab with FOLFOX chemotherapy in previously untreated HER2-amplified metastatic gastroesophageal adenocarcinoma. Abstract CT174.  AACR Annual Meeting. 2021. 

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