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MSI-H CRC Adjuvant Chemo — SCE Medical Oncology MCQ

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HardGI CancersMSI-H CRC Adjuvant ChemoSCE Medical Oncology

A 50-year-old man with Lynch syndrome (MLH1 mutation) develops colorectal cancer and is treated with curative resection and adjuvant chemotherapy. What specific chemotherapy consideration applies to Lynch syndrome-associated MSI-H colorectal cancer?

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Correct answer: E — 5-FU monotherapy may have reduced benefit in MSI-H CRC (controversial)

The benefit of adjuvant 5-FU monotherapy in MSI-H stage II colon cancer is debated — some data suggest no benefit or even potential harm, possibly because MSI-H tumours have inherent chemoresistance to 5-FU through MMR-dependent drug-induced apoptosis pathways. However, oxaliplatin-containing regimens (FOLFOX/CAPOX) retain benefit regardless of MSI status. For stage II MSI-H CRC, the excellent prognosis (low recurrence risk) further questions the need for adjuvant chemotherapy. This is distinct from metastatic MSI-H CRC where immunotherapy is first-line.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/cancer