Pembrolizumab (PD-1) neoadjuvant delivers 80% 3-yr EFS in dMMR/MSI-H tumors; ctDNA pinpoints relapse risk

Phase II NCT04082572 enrolled 35 patients with locally advanced dMMR/MSI-H solid tumors who received neoadjuvant pembrolizumab; at 3 years, event-free and overall survival reached 80% (95% CI 66-93) and 94% (86-100). Post-treatment ctDNA status was highly prognostic: ctDNA-negative vs -positive patients showed 3-yr EFS 92% vs 20% and OS 100% vs 80% (p<0.001); in the colorectal subset, ctDNA-negative cases achieved 91% pathologic CR versus 0%, with watch-and-wait management yielding 2-yr EFS 100% vs 33%. No late safety concerns emerged.