New Reference: Perioperative Pembrolizumab for MSI-H/dMMR Colorectal Cancer

In this phase II trial of patients with localized dMMR/MSI colorectal cancer, perioperative pembrolizumab achieved a pathologic complete response rate of 53%. Treatment was feasible and safe with manageable immune-related adverse events, though one treatment-related death (myasthenia) occurred. Longer follow-up is needed to confirm survival benefits.

Study

Prospective multicenter, nonrandomized phase II trial [IMHOTEP]

Localized resectable dMMR/MSI colorectal cancer

Pembrolizumab 400 mg IV once every 6 weeks, 1 or 2 cycles neoadjuvant then up to 1 year total (n=89 enrolled, n=72 evaluable for pCR)

Efficacy

pCR: 52.7% (38/72)

24-month OS: 98%

Safety

Grade >=3 immune-related AEs: 15.7%

Grade 5 treatment-related AE: myasthenia (1.1%)

Postoperative surgical complications: 15.4% (12/78 patients)

Treatment discontinuation due to AE: 26.4%

J Clin Oncol 2026;44:1520-1528

de la Fouchardiere C, Zaanan A, de Montfort A Efficacy of Perioperative Pembrolizumab in Mismatch Repair Deficient/Microsatellite Unstable Localized Colorectal Cancers: Results of the Phase II Trial IMHOTEP

http://doi.org/10.1200/JCO-25-02169

Reviewed by Ulas D. Bayraktar, MD on Jun 17, 2026

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