Neoadjuvant immunotherapy in dMMR/MSI colorectal cancer

In this video, Dr Annalice Gandini and Dr Gertjan Rasschaert discuss the AGEO-NEO-MSI study, presented at ESMO GI 2026 in Munich.¹ This international real-world cohort evaluated neoadjuvant immune checkpoint inhibition in patients with non-metastatic dMMR/MSI colorectal cancer. The study included 316 patients from more than 30 centres, mainly in Europe but also in the United States, and aimed to assess whether the strong results seen in phase II trials could be reproduced in routine clinical practice. Most patients received single-agent immunotherapy (77%), while around one quarter received doublet immunotherapy.

The primary endpoint was complete response, defined as either pathological complete response in patients undergoing surgery or clinical complete response in those managed non-operatively. Overall, neoadjuvant immunotherapy showed substantial activity, with a complete response rate of 67% and a pathological complete response rate of 66%. 

Event-free survival data remain immature, with a median follow-up of 16 months. The 1-year event-free survival rate was 92%, and the 2-year rate was 86%. Doublet treatment was associated with numerically higher event-free survival rates compared with monotherapy, but also with more grade ≥3 immune-related adverse events (12.5% versus 4.5%), highlighting the need to balance efficacy and toxicity on an individual basis.