The study was done to evaluate the antitumor activity of pembrolizumab, pembrolizumab plus chemotherapy, or chemotherapy alone in patients with untreated, advanced G/GEJ cancer with PD-L1 CPS of 1 or greater.

The study enrolled 763 patients with untreated, locally advanced/unresectable or metastatic G/GEJ cancer with PD-L1 CPS of 1 or greater.

Primary endpoints were OS and PFS in patients with PD-L1 CPS of 1 or greater or 10 or greater.

A total of 763 patients were randomized. At final analysis, after a median follow-up of 29.4 months, pembrolizumab was non-inferior to chemotherapy for OS in patients with CPS of 1 or greater. Pembrolizumab monotherapy was not superior to chemotherapy in patients with CPS of 1 or greater. Pembrolizumab prolonged OS vs chemotherapy in patients with CPS of 10 or greater, but this difference was not statistically tested. Pembrolizumab plus chemotherapy was not superior to chemotherapy for OS in patients with CPS of 1 or greater or CPS of 10 or greater or for PFS in patients with CPS of 1 or greater. Grade 3 to 5 treatment-related adverse event rates for pembrolizumab, pembrolizumab plus chemotherapy, and chemotherapy were 17%, 73%, and 69%, respectively.

This study concluded that among patients with untreated, advanced G/GEJ cancer, pembrolizumab was non-inferior to chemotherapy, with fewer adverse events observed. Pembrolizumab or pembrolizumab plus chemotherapy was not superior.

Reference: https://jamanetwork.com/journals/jamaoncology/article-abstract/2769922