Bone Marrow Fibrosis as a Predictor of Extramedullary Disease in Multiple Myeloma

The correlation between bone marrow fibrosis (BMF) and extramedullary disease has yet to be fully elucidated in patients with newly diagnosed multiple myeloma. Therefore, we aimed to analyze the incidence of BMF in newly diagnosed multiple myeloma patients and evaluate the relationship between BMF and synchronous soft tissue extramedullary involvement at diagnosis. A retrospective chart review was conducted on a total of 356 patients with multiple myeloma. Patients' clinical characteristics, treatment outcomes, and histological features were systematically collected. The degree of BMF was graded according to the World Health Organization criteria. Patients with Grade 2 and 3 BMF were classified into the fibrosis group, whereas those with Grade 0 or 1 were categorized into the non-fibrosis group. Extramedullary disease was defined as soft tissue tumors arising from hematogenous spread without any contiguous contact with bony structures. Finally, clinical and laboratory parameters were compared between the fibrosis and non-fibrosis groups. Of the 356 patients, 146 (41%) presented with Grade 2 or higher levels of BMF. Extramedullary disease was detected in 52 patients (14.6%), while 54 patients (15.2%) had paraskeletal plasmacytoma. Grade 2 or 3 BMF was observed in 40 of the 52 patients with extramedullary disease (p < 0.01). Consistently, in the 210 patients without BMF, EMD was absent in 198 cases (p < 0.01). In multivariable logistic regression analysis, BMF status (OR = 3.200, 95% CI: 1.010-10.141, p = 0.048) and elevated serum lactate dehydrogenase (LDH) levels (OR = 1.003, 95% CI: 1.000-1.005, p = 0.037) were identified as independent predictors of synchronous extramedullary disease. In conclusion, our study indicates that increased BMF in patients with multiple myeloma is closely associated with synchronous extramedullary dissemination. Consequently, evaluating BMF at initial diagnosis may serve as a useful surrogate marker to identify patients presenting with concurrent extramedullary involvement.