The Prevalence and Clinical Impact of Bone Marrow Fibrosis in Chronic Myeloid Leukemia

INTRODUCTION: Bone marrow fibrosis may be present at chronic myeloid leukemia (CML) diagnosis and has been historically associated with poorer treatment responses. Its prognostic value is unclear for clinical outcomes in the current tyrosine kinase inhibitor (TKI) era. METHODS: We conducted a single-center retrospective study including patients with a bone marrow biopsy at diagnosis. Fibrosis was graded according to the WHO classification. We assessed the prevalence of bone marrow fibrosis at diagnosis and its association with later clinical outcomes: the achievement of MR4.0 (BCR::ABL1 ≤0.01% IS) and sustained treatment-free remission (TFR) at 12 months after TKI stop. RESULTS: Among 50 CML patients, 56% had bone marrow fibrosis, mostly grade 1 (n = 23) and less often grade 2 (n = 5). Forty-one of the 50 patients (82%) achieved MR4.0. MR4.0 achievement was not associated with fibrosis status (p = 0.40). Twenty-seven of the 50 patients (54%) discontinued their TKI with available outcome data. Among the 27 patients who stopped, 21 (78%) had a molecular relapse, the occurrence of which was not associated with fibrosis status (p = 0.65). CONCLUSIONS: Low-grade bone marrow fibrosis is prevalent at CML diagnosis but is not associated with the achievement of MR4.0 or sustained TFR.