Background Basophilia is common in chronic myeloid leukaemia (CML) and is associated with a poor prognosis. Previously it was quantified by percentage and a binary < or ≥ 20%. However, blood basophil concentration at diagnosis may be a better prognostic co-variate.

Methods The hypothesis generating cohort was a 135 newly-diagnosed subjects with BCR::ABL1-positive CML receiving a tyrosine kinase-inhibitor (TKI). Median follow-up was 6.3 years (range, 4-16 years). Data were analyzed by Kaplan-Meier curves and multi-variable patient similarity network (PSN). A cohort of 1919 subjects was used to validate the test hypothesis. Subject gave informed consent for non-interventional data collection and the study was approved by Ethics Committees.

Results Multi-variable PSNs of the hypothesis generating cohort indicated 5 subject clusters. Incidence of TKI switch was highest in clusters 1 (45%), 5 (40%) and 4 (30%) which were characterized by the increased basophil concentrations at diagnosis compared with clusters 2 (13%) and 3 (14%) with the low basophil concentrations at diagnosis. PSNs identified the combination of basophil concentration ≥ 8x10E+9/L, basophil percentage ≥ 5 % and WBC ≥ 164x10E+9/L to be associated with significantly worse FFS (p < 0.001) and PFS ( p = 0.02) but not survival ( p = 0.18). Basophil concentration ≥ 8x10E+9/L and WBC concentration ≥ 164x10E+9/L were associated with worse EFS (p < 0.001), (FFS (p < 0.001; Figure 1) but not PFS or survival. Basophil percentage at diagnosis had no impact on outcomes using ≥ 5% or ≥ 20% cutoffs. In the validation cohort the combination of basophil concentration ≥ 8x10E+9/L, basophil percentage ≥ 5% and WBC ≥ 164x10E+9/L at diagnosis was associated with worse FFS ( p < 0.001) but not PFS or survival. Basophils ≥ 5% was associated with worse survival ( p = 0.04) and ≥ 20% with worse FFS ( p = 0.04) and survival ( p = 0.009). Basophil concentration ≥ 8×10E+9/L was associated with worse PFS ( p < 0.001; Figure 1) and survival ( p = 0.03). There was no effect of WBC concentration on any outcome.

Conclusion We show blood basophil concentration at diagnosis correlates with diverse outcomes in newly-diagnosed persons with CML receiving TKI-therapy.

Support IGA_LF_2023_05, MH_CZ-DRO (FNOL, 00098892)

Faber:Angelini Pharma: Honoraria, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Zentiva: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

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2023
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