A Higher Neutrophil Count Is Associated with Favorable Achievement of Treatment-Free Remission in Patients with Chronic Myeloid Leukemia Who Received Second Generation Tyrosine Kinase Inhibitor as Frontline Treatment

Background: ABL1 tyrosine kinase inhibitor discontinuation securely became among the therapeutic goal for chronic myeloid leukemia chronic phase patients (CML-CP). To establish successful prognostic factors for treatment-free remission (TFR), it is necessary to diagnose the patients with high-risk molecular relapse, however, a biomarker for the achievement of TFR has not been completely elucidated. Recent investigations have determined that neutrophils function crucially in cancer immunology. Patients and Methods: The research was a multicenter retrospective observational study to examine the correlation between TFR and neutrophil counts before TKI discontinuation. The investigation included patients having Philadelphia chromosome-positive CML-CP who attempted the discontinuation of TKIs after a durable deep molecular response between January 2012 and July 2021 at four institutions in Japan. Results: 118 CML-CP patients in total discontinued TKIs and an estimated 36-month TFR rate was 65.1%. 52 patients received second-generation TKIs as frontline. Higher neutrophil count (>3210/mu L) at TKIs discontinuation was determined as an independent prognostic variable for TFR in patients who received second-generation TKIs as frontline [(HR, 0.235 (95%, confidence interval (CI) 0.078-0.711); p = 0.010]. Conclusions: The neutrophil-mediated immunomodulation can be a significant component for the effective achievement of TFR in CML supported by our clinical observation.