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Tumour Marker Flare — SCE Medical Oncology MCQ

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ModerateBreast CancerTumour Marker FlareSCE Medical Oncology

A 62-year-old woman with metastatic ER+/HER2- breast cancer has bone flare on starting endocrine therapy. Her CA15-3 rises from 45 to 120 U/mL at 4 weeks. CT shows no new lesions. What tumour marker pattern supports tumour flare rather than progression?

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Correct answer: B — A transient rise in CA15-3 within the first 8-12 weeks of endocrine therapy followed by subsequent decline is consistent with flare — serial monitoring rather than single readings guides decisions

Tumour marker flare (transient rise in CA15-3 or CEA) occurs in ~15-25% of patients starting endocrine therapy for metastatic breast cancer. It typically peaks at 4-8 weeks then declines. A single elevated reading should not trigger treatment change — serial monitoring over 8-12 weeks is recommended. ESMO guidelines caution against changing treatment based on marker rise alone without confirmatory imaging evidence of progression.

Reference: ESMO 2024 MBC Guidelines; Robertson et al Br J Cancer 1999