A 55-year-old presents with fatigue, splenomegaly, and leukocytosis (WBC 180 × 10⁹/L) with basophilia. BCR-ABL1 fusion gene (Philadelphia chromosome) is detected. He is started on imatinib 400 mg daily. At 3 months, BCR-ABL1 transcript on quantitative PCR is 12% IS (international scale). According to ELN 2020 response criteria, this represents:
- A Optimal response
- B Treatment failure; switch to a 2nd-generation TKI (nilotinib or dasatinib)
- C Warning; continue imatinib but increase monitoring frequency ✓
- D Major molecular response (MMR) achieved
Correct answer: C. Warning; continue imatinib but increase monitoring frequency
Explanation
ELN 2020 criteria define optimal response at 3 months as BCR-ABL1 ≤10% IS. A result between 10–35% IS at 3 months is classified as 'Warning' — it does not mandate immediate TKI switch but requires closer monitoring and reassessment at 6 months. Treatment failure is BCR-ABL1 >35% IS (no cytogenetic response) at 3 months, which requires TKI switch. MMR is BCR-ABL1 ≤0.1% IS.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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