Deep molecular responses achieved in chronic myeloid leukemia in chronic phase patients with BCR-ABL1 >10% at 3 months who are early switched to nilotinib

Objectives: There are still controversies about whether or when to change therapy for those chronic myeloid leukemia in chronic phase (CML-CP) patients with BCR-ABL1 transcript level at 3 months higher than 10%. Here we studied the clinical significance of early switching to nilotinib in CML-CP patients with BCR-ABL1 >10% at 3 months. Methods: We investigated 495 first-line imatinib-treated patients with CML-CP and identified 117 (23.6%) patients with BCR-ABL1 >10% at 3 months, including 46 patients with warning response defined according to ELN-2013 recommendations. In 46 patients with warning response, 26 of them continued imatinib therapy and 20 patients early switched to nilotinib therapy. Results: Compared to continued imatinib group, nilotinib group showed significantly higher percentage achieving BCR-ABL1 <1% at 6 months (85.0% vs. 19.2%, P = 0.0004), better cumulative rates of MR3.0 and MR4.0 of 4 years (82.1% vs. 41.2%, P = 0.0091; 61.5% vs. 18.6%, P = 0.035). Conclusion: In summary, early switching to nilotinib enabled more CML-CP patients with warning molecular response at 3 months to achieve early and deeper molecular response vs. remaining on imatinib.