CRC Sidedness — SCE Medical Oncology MCQ
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Correct answer: C — Prefer an anti-EGFR strategy for fit left-sided all-RAS-wild-type disease
Primary sidedness and complete RAS status support an anti-EGFR plus chemotherapy strategy in fit left-sided all-RAS-wild-type metastatic colorectal cancer. Prefer an anti-EGFR strategy for fit right-sided all-RAS-wild-type disease: right-sided primary location predicts less first-line benefit from anti-EGFR treatment. Prefer bevacizumab for fit left-sided all-RAS-wild-type disease: bevacizumab is active, but left-sided all-RAS wild type is the setting favouring anti-EGFR selection. Prefer an anti-EGFR strategy for fit left-sided KRAS-exon-two-wild-type disease: extended KRAS and NRAS wild-type status is required, not exon two alone. Prefer anti-EGFR monotherapy for fit left-sided all-RAS-wild-type disease: fit first-line patients generally receive the antibody with a chemotherapy doublet.
Reference: Primary-tumour side as a driver of first-line treatment in RAS-wild-type metastatic colorectal cancer (Published April 2023): https://pubmed.ncbi.nlm.nih.gov/36913832/; Erbitux UK summary of product characteristics (Updated September 2025): https://www.medicines.org.uk/emc/product/317/smpc