Triple combination treatment of trastuzumab, chemotherapy and immune checkpoint inhibitor in HER2 positive unresectable, locally advanced, metastatic gastric and esophageal adenocarcinoma: A systematic review and meta-analysis.

Abstract

e16071 Background: The current standard of care for unresectable, locally advanced or metastatic HER2 positive gastric, esophageal and gastroesophageal junction adenocarcinomas is the combination of the anti HER 2 antibody trastuzumab and cytotoxic chemotherapy. In recent years, the addition of immune checkpoint inhibitors to this combination has been studied to determine if it can improve clinical outcomes for this disease. This systematic review and meta-analysis evaluated high-quality data from clinical trials to determine the role and efficacy of this triple combination treatment. Methods: A systematic search of English-language articles on PubMed, Cochrane and Google scholar was done to identify randomized trials (RCTs) investigating the use of triple combination treatment of anti-Her 2 antibody, chemotherapy and immune checkpoint inhibitor in the treatment of unresectable, locally advanced, or metastatic HER2 overexpression positive gastric, esophageal and gastroesophageal junction adenocarcinoma. Quality of the studies was assessed using the Revised Cochrane risk-of-bias tool for randomized trials (RoB 2). Inverse variance was the statistical method used with random effects as the analysis model in the production of the Forest plot and calculation of risk ratio (RR) at 95% confidence intervals (CI). Results: Four (4) RCTs (N = 866) were included for quality assessment and data extraction. Two (2) of these RCTs (N = 80) were single arm studies which both showed favorable outcomes in terms of objective response rate and progression free survival. The two (2) other RCTS (N = 786), each had two arms (triple regimen versus comparator) and were used in the meta-analysis. Risk of bias was low and heterogeneity was low (I2 below 50%). Pooled results showed that in patients given triple combination regimen, there is statistically significant improvement in progression free survival (RR 1.55 95% CI 1.20-2.00, p 0.0007). There is also an increase in overall response rate in favor of the triple combination regimen, albeit not statistically significant (RR 1.31 95% CI 0.99-1.74, p = 0.06). Conclusions: The addition of an immune checkpoint inhibitor to the current standard of care of anti Her 2 antibody and chemotherapy provides meaningful results in terms of tumor response and progression free survival in Her 2 positive locally advanced or metastatic gastric and esophageal adenocarcinomas. More robust trials, and data on overall survival supporting the use of this triple regimen may help re-shape the current standard of care for this disease.