Evaluation of factors affecting extramedullary involvement in patients with multiple myeloma at the time of diagnosis

Introduction and Aim: Multiple Myeloma (MM) is a neoplasm of clonal plasma cells based on B cells and, although known as a rare disease, it is the second most common malignancy among hematological cancers when assessed. Its frequency is higher in the elderly population, with a median age at diagnosis between 66 and 70 years old.1 Extramedullary myeloma can be defined as the presence of plasma cells outside the bone marrow in MM patients.76 This retrospective study aims to evaluate the factors affecting extramedullary involvement at the time of diagnosis in patients with Multiple Myeloma. Materials and Methods: The study was conducted retrospectively with the participation of two centers in Turkey (Çukurova University Faculty of Medicine and Adana City Hospital). A total of 144 patients aged 18 and older who were followed for Multiple Myeloma (MM) between 2010-2022 were included in the study. At the time of diagnosis, patients' complete blood counts, biochemical tests, and laboratory measurements that have been proven important in the diagnosis, follow-up, and prognosis of the disease were performed. Imaging methods were used at the time of diagnosis to examine the location and number of extramedullary involvement, if present, and the location and number of accompanying lytic lesions, if any. Patients were subjected to proven prognostic staging systems. Results: The mean age of the patients was 60.5±10.3 years, while 54,9% of them were male. The presence of lytic lesions in patients was 51,4%, and the presence of plasmacytoma was 30,6%. The frequency of being R-ISS stage III was higher in patients with lytic lesions. The lytic lesion rate was found to be higher in the presence of plasmacytomas. The rate of being R-ISS stage III and ISS stage III was higher in patients with plasmacytomas. In the presence of plasmacytoma, LDH, beta-2 microglobulin, and erythrocyte sedimentation rate values were measured to be statistically significantly higher than those without plasmacytoma. Conclusion: The presence of extramedullary involvement or lytic lesions at the time of diagnosis in patients with multiple myeloma is a marker of poor prognosis. This situation is as important as staging, in choosing the appropriate treatment. In our study, poor prognostic factors such as higher beta-2 microglobulin, increased LDH, increased erythrocyte sedimentation rate, and more frequent lytic lesions were found more frequently in patients with extramedullary involvement. Keywords: Multiple Myeloma, extramedullary involvement, lytic lesion, prognosis