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Liquid Biopsy — SCE Medical Oncology MCQ

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ModerateLung CancerLiquid BiopsySCE Medical Oncology

A 55-year-old woman with EGFR-mutant NSCLC is on osimertinib. Her oncologist orders regular ctDNA (circulating tumour DNA) monitoring. What is the primary clinical utility of ctDNA monitoring during targeted therapy?

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Correct answer: B — Early detection of molecular resistance (e.g. C797S, MET amplification) before radiographic progression, guiding early treatment adaptation

Liquid biopsy (ctDNA) enables non-invasive molecular monitoring during targeted therapy. Rising ctDNA or detection of resistance mutations (C797S, MET amplification, EGFR C797S) can precede RECIST-defined radiographic progression by weeks-months, potentially allowing earlier intervention. It also detects molecular heterogeneity that tissue biopsy may miss. While not yet standard of care for treatment modification decisions, ctDNA monitoring is increasingly used in clinical practice and trials.

Reference: ESMO 2024 NSCLC Guidelines; ESMO Liquid Biopsy Recommendations 2024