A 58-year-old man is diagnosed with CML in chronic phase. BCR-ABL p210 fusion is confirmed. He is started on imatinib 400 mg/day. At 3 months, BCR-ABL transcript level by RT-PCR is 12% IS. What does this indicate and what is the next step?
- A Optimal response; continue imatinib and reassess at 6 months
- B Treatment failure; switch to dasatinib immediately
- C Warning response; check ABL kinase domain mutation and consider switch ✓
- D Complete cytogenetic response achieved; reduce imatinib dose
Correct answer: C. Warning response; check ABL kinase domain mutation and consider switch
Explanation
According to ELN 2020 CML guidelines, BCR-ABL >10% IS at 3 months defines a 'warning' response (not failure or optimal). An optimal response at 3 months is BCR-ABL ≤10% IS. In the warning zone, kinase domain mutation testing is recommended and closer monitoring or switch to a 2nd-generation TKI (dasatinib, nilotinib, bosutinib) should be considered. Immediate switch without mutation analysis is not the standard. A 12% IS does not represent complete cytogenetic response.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.