Immune-Checkpoint Inhibitors (ICIs) in Metastatic Colorectal Cancer (mCRC) Patients beyond Microsatellite Instability

Area of Science:

• Oncology
• Immunotherapy
• Genetics

Background:

• Immune-checkpoint inhibitors (ICIs) demonstrate significant efficacy in metastatic colorectal cancer (mCRC) with deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H) tumors.
• However, a subset of these dMMR/MSI-H mCRC patients exhibit primary resistance to immunotherapy, necessitating further investigation into underlying mechanisms.
• Current challenges include determining optimal treatment duration and managing secondary resection of metastases in patients receiving ICIs.

Purpose of the Study:

• To review recent literature on ICIs in mCRC, focusing on dMMR/MSI-H and specific patient subgroups.
• To identify potential new predictive biomarkers for ICI efficacy beyond microsatellite status.
• To explore future therapeutic targets and strategies for optimizing immunotherapy in mCRC.

Main Methods:

• Literature review of recent studies on immune-checkpoint inhibitors in metastatic colorectal cancer.
• Analysis of predictive biomarkers, including microsatellite instability, Tumor Mutational Burden, and PD-L1 expression.
• Focus on dMMR/MSI-H tumors and special subgroups, such as those with POLE mutations.

Main Results:

• Microsatellite status (dMMR/MSI-H) is a key predictor of ICI response in mCRC.
• Primary resistance to ICIs occurs in a proportion of dMMR/MSI-H mCRC patients.
• POLE-mutated pMMR/MSS CRC tumors may also benefit from ICIs due to a hypermutated phenotype.

Conclusions:

• Understanding the biological mechanisms of dMMR/MSI-H CRC and immune response is crucial for improving ICI efficacy.
• Tumor Mutational Burden and PD-L1 expression are being investigated as complementary predictive biomarkers.
• Further research is needed to personalize immunotherapy strategies and overcome resistance in mCRC.