Overall, 18 pts with MSI/dMMR resectable cT2-4 any N GAC/GEJAC were recruited in Cohort 1….Among 15 evaluable patients, 1 had disease progression and 14 underwent resection. pCR rate was 60% (9/15) and major-complete pathological response (<10% viable cells) was 80%....Pre-operative T300/D for 3 months was safe and provided promising proof of efficacy in MSI, dMMR GAC/GEJAC pts.