Watch-and-Wait Approach With Dostarlimab in Localized dMMR/MSI-H Gastric Cancer: GERCOR Phase II Study

"After inclusion: dostarlimab 500mg IV 30min q3w (± 2-3 days) for 4 cycles (C1-C4)~Then:~At wk12 • If cCR: dostarlimab 1000mg q6w for 2 cycles (C5-C6)~• If downstaging at UGI endoscopy, and no disease progression (PD)/or mets on TAP-CT, \<3 biopsies with tumor cells: dostarlimab 500mg q3w for 4 cycles (C5-C8)~• If loco/loco-regional PD on TAP-CT, macroscopic tumor on UGI endoscopy, no distant mets, and \>2 positive biopsies at wk12 followed by surgery and if Becker-TRG 1a, 1b, or 2 after surgery: dostarlimab 1000mg q6w for 6 cycles (C5-C10)~At 24wk~• If cCR at 12 and 24 wks: dostarlimab 1000mg q6w for 4 cycles (C7-C10)~• If downstaging at UGI endoscopy without PD on CT at wk 12 with \<3 biopsies with tumor cells at wk12 and cCR: dostarlimab 1000mg q6w for 4 cycles (C9-C12)~• If downstaging at UGI endoscopy without PD on CT at wk 12 with and no cCR, surgery will be proposed and if Becker-TRG 1a, 1b, or 2 after surgery: dostarlimab 1000mg q6w for 4 cycles (C9-C12)"