Baseline Cytogenetic Response Level Impact on Survival of Chronic Phase Chronic Myeloid Leukemia Patients Treated with Tyrosine Kinase Inhibitors as Third-Line Therapy: Real-World Data in Five Russian Centers

Context Tyrosine kinase inhibitors in third-line therapy (TKI-3L) in chronic-phase chronic myelogenous leukemia (CP CML) is effective in a portion of patients. Meanwhile, it is unclear which patients may benefit from TKI-3L. Objective To identify the factors affecting the outcome of TKI-3L therapy in CP CML. Design A retrospective study was conducted in five centers of St. Petersburg and Leningrad Region in 2019. All CP CML patients who ever obtained TKI-3L in these centers were included, except patients (pts) with complete cytogenetic response (CCyR). Results Seventy-three pts (male=26) with baseline median age 51 (25–88) were included in the study. There were 51 (70%) pts without any CyR, including 27 (37%) cases without complete hematologic response in baseline. For other patients, the best baseline cytogenetic response was minimal or minor (mmCyR) in 12 (16%) and partial (PCyR) in 10 (14%). BCR-ABL mutations were detected in 30/73 (42%) cases at any time before TKI-3L. Reasons for switching to TKI-3L were resistance in 56 (77%) or intolerance in 17 (23%). Dasatinib, Nilotinib, Bosutinib, or Ponatinib were used as TKI-3L in 43 (59%), 18 (25%), 9 (12%), and 3 (4%) pts, respectively. The median time of TKI-3L treatment duration was 15 (1–120) months. CCyR was achieved in 8/51 (16%) and 14/22 (64%) pts without CyR and with mmCyR/PCyR, respectively(p=0.001). CCyR subsequently had been lost 5/8 (62.5%) and 5/14 (29%) pts initially without or with any CyR (p=0.01). MMR was achieved in 3/51 (6%) and 6/22 (27%) pts without or with any CyR (p>0.05). Estimated overall 1-year, 3-year, and 5-year OS were 95%, 81%, and 65%, respectively. The median follow-up was 26 (3–136) months. There were 14 (19%) death: 11 due to CML progression and 3 after allo-SCT. All deaths occurred in pts without any CyR at baseline. Transformation to accelerated phase and blast crisis was occurred in 13 (18%) pts only in pts group without any CyR initially. The median time to progression was 15 (6–102) months. The only relevant baseline factor for CCyR, OS, and PFS probability in multivariant analysis was the presence of any CyR at baseline (p Conclusion Initial presence of any CyR was a favorable factor for long-term results of TKI third-line treatment in CP CML. TKI-3L should be considered as an appropriate tool in CML treatment for this group.