Prognostic Implications and Clinical Characteristics Associated with Bone Marrow Fibrosis in Patients with Myelofibrosis

Abstract

Abstract▪2824▪This icon denotes a clinically relevant abstract Background:Myelofibrosis (MF) is a heterogeneous, hematopoietic stem cell malignancy characterized by abnormal proliferation of myeloid cells with varying maturity and function. Bone marrow fibrosis (BMF), which results from abnormal deposition of stromal reticulin and collagen fibers, plays a major role in the pathophysiology of MF. Objectives:To investigate the characteristics associated with the extent of BMF and its implications on the clinical manifestation, overall survival (OS), event-free survival (EFS), and transformation to acute leukemia in patients with primary or secondary myelofibrosis. Methods:We conducted a retrospective chart review analysis of 514 patients who were diagnosed with myelofibrosis according to World Health Organization criteria (353 patients with primary myelofibrosis, 82 with post polycythemia vera [Post-PV] MF, and 79 with post essential thrombocythemia [Post-ET] MF) and were referred to MD Anderson Cancer Center between February 2005 and December 2009. Results of the first bone marrow biopsy done at MD Anderson were reviewed. BMF was documented according to the European consensus grading system (MF 0–3), in which MF-3 is the most severe grade of fibrosis. Result:Of 514 patients, 7 (1%) had MF-0, 44 (9%) had MF-1, 171 (33%) had MF-2, and 292 (57%) had MF-3. Table 1 summarizes patient characteristics and outcomes by grade. Conclusion:Severe bone marrow fibrosis was associated with lower Hgb, lower WBC count, larger spleen and abnormal cytogenetics. There was no association between JAK2 mutation and the severity of BMF. The OS, EFS and transformation to leukemia were similar among patients with various degrees of fibrosis. Similar results were achieved in patients with primary, post-PV MF, and post-ET MF. This might explain the heterogeneity of the disease course and its prognosis. Longer follow-up is needed to further investigate the impact of BMF on OS, EFS and PFS.Table 1:Patients characteristics and outcomes by gradeNumber of patients (%) or median value (range)MF-0MF-1MF-2MF-3p valuePatients7 (1%)44 (9%)171 (33%)292 (57%)Age, years65 (53–81)65 (31–82)63 (20–86)64 (21–89)0.644Male2/7 (28%)30/44 (68%)104/171 (61%)176/292 (60%)0.253Female5/7 (72%)14/44 (32%)67/171 (39%)116/292 (40%)Hgb10.6 (8.1–12.7)11.05 (7.9–16.4)11 (6–16.80)10 (5.4–18.7)<0.001WBC11.4 (4.4–30.8)14.4 (1.3–188)9.5 (1.4–182)10.1 (1–361)0.036Liver size (cm)0 (0–5)0 (0–12)0 (0–14)0 (0–30)0.046Spleen size (cm)3 (0–20)9 (0–99)6 (0–99)12 (0–99)0.005Constitutional symptoms3/7 (43%)23/44 (52%)76/171 (44%)148/292 (51%)0.569Transfusion dependency2/7 (28%)6/44 (14%)31/171 (18%)80/292 (27%)0.052Abnormal cytogenetics0 (0%)14/44 (32%)48/171 (28%)117/292 (40%)0.012(+) JAK2 mutation2/7 (28%)25/44 (57%)108/171 (63%)179/292 (61%)0.288Leukemia transformation0 (0%)0 (0%)10/171 (6%)19/292 (7%)0.350OSNot reachedNot reached47.2 (0–63.7)39.9 (0–77.5)0.825EFSNot reachedNot reachedNot reachedNot reached0.302Post-PV MF pts %1/7 (14%)4/44 (9%)24/171 (14%)53/292 (18%)0.380Post-ET MF pts %1/7 (14%)10/44 (23%)30/171 (17%)38/292 (13%)0.296 Disclosures:No relevant conflicts of interest to declare.