Efficacy of immunotherapy in gastrointestinal (GI) tumors with mismatch repair deficient (MMRd) unusual phenotype: an AGEO real-world study.

ABSTRACT:

Background

Tumors with mismatch repair deficiency (MMRd) classically display concomitant loss of MLH1/PMS2 or MSH2/MSH6 on immunohistochemistry (IHC) with microsatellite instability-high (MSI-High) status on molecular testing. Nevertheless, a different phenotype can occur in up to 15% of MMRd tumors (unusual phenotype). Data on the efficacy of immunotherapy in this population remain scarce.

Methods

We conducted a retrospective study within the IMMUNODIG MSI cohort including patients with advanced gastrointestinal MMRd tumors treated with immune checkpoint blockade in the real-world setting. We selected patients with both IHC and MSI assays data available. Unusual MMRd tumors were classified into four distinct groups: (1) isolated loss of PMS2 or MSH6 with MSI-H (isolated/MSI

SUBMITTER: Alouani E 

PROVIDER: S-EPMC12574357 | biostudies-literature | 2025 Oct

REPOSITORIES: biostudies-literature