A patient with Stage III colon cancer (pT3N2aM0) completes curative resection. Microsatellite instability (MSI) testing shows MSI-High status. Regarding adjuvant chemotherapy, which statement is most accurate based on current evidence?

• A MSI-H status predicts superior benefit from 5-FU monotherapy adjuvant chemotherapy
• B MSI-H Stage III patients have improved prognosis and do not benefit from adjuvant chemotherapy
• C MSI-H status is a contraindication to adjuvant chemotherapy; immunotherapy should be used instead
• D MSI-H Stage III patients should receive FOLFOX adjuvant chemotherapy as the predictive benefit of oxaliplatin-based regimens is not negated by MSI-H status ✓

Explanation

MSI-H (microsatellite instability-high) colorectal cancer confers better prognosis and, crucially, predicts lack of benefit from 5-FU monotherapy adjuvant chemotherapy (Stage II MSI-H patients do not benefit from adjuvant 5-FU). However, for Stage III MSI-H patients, oxaliplatin-containing regimens (FOLFOX, CAPOX) remain the standard of care because the negative predictive effect of MSI-H applies primarily to fluoropyrimidine monotherapy, not oxaliplatin combinations. Adjuvant immunotherapy for Stage III MSI-H CRC is not yet standard outside trials.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.