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Endocrine Resistance — SCE Medical Oncology MCQ

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ModerateBreast CancerEndocrine ResistanceSCE Medical Oncology

A 60-year-old woman with metastatic breast cancer asks about the difference between endocrine resistance categories. She progressed 6 months into first-line AI therapy. How is this classified?

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Correct answer: B — Primary endocrine resistance — defined as relapse within the first 2 years of adjuvant ET or progression within 6 months of first-line ET for metastatic disease; secondary resistance is progression after ≥6 months of ET benefit

ESMO defines endocrine resistance categories: PRIMARY resistance — relapse ≤2 years on adjuvant ET or progression ≤6 months on first-line ET for advanced disease. SECONDARY (acquired) resistance — relapse >2 years on adjuvant ET (or ≤12 months of completing adjuvant ET) or progression after ≥6 months of benefit on ET for advanced disease. This distinction guides treatment: primary resistance suggests consideration of chemotherapy; secondary resistance supports further endocrine-based approaches (alternative ET ± CDK4/6i, PI3Ki, mTORi).

Reference: ESMO 2024 MBC Guidelines; Cardoso et al Ann Oncol 2018