Bone marrow microenvironment is an area of interest. Reticulin fibers are a natural component of the microenvironment. Bone marrow fibrosis (BMF) is defined as an increase in reticulin fibers in the bone marrow. In this study, we aimed to explore the frequency of BMF at diagnosis, to investigate differences between BMF and non-BMF patients and the impact of BMF on disease course.

This single-center retrospective study included patients who had been diagnosed with multiple myeloma (MM) and had been evaluated for BMF between January 2010 and June 2022 with a follow-up period of at least 1 year.

A total of 217 patients were subdivided into two groups, namely those with (n=137) and without BMF (n=80). The median follow-up time was 44 months (range 12-155). We did not detect any survival difference between patients with and without BMF at diagnosis. However MM with BMF patients had lower hemoglobin values, higher International Staging System (ISS) stages and a tendency towards diffuse plasma cell infiltration and autologous stem cell transplantation (ASCT) was performed less frequently in this patient group. Post-treatment bone marrow biopsies revealed that fibrosis had regressed or completely disappeared in 72% of the patients.

BMF was observed in 63% of the patients. While fibrosis was not found to be independently associated with survival, diffuse plasma cell infiltration pattern, deeper anemia and higher ISS were found to be related to the fibrosis. Older age and red blood cell (RBC) transfusion need correlated with worsening progression free survival (PFS) and overall survival (OS) in patients with BMF.