Multiple Myeloma Complicated by Bone Plasmacytomas: Pathogenesis, Clinical Features, Treatment Approaches (A Literature Review)

Bone plasmacytoma is a malignant neoplasm consisting of plasma cells. It develops in the medullary cavities of the skeletal bones. The tumor can destroy bone cortex and proliferate into the surrounding tissues. In contrast to bone plasmacytomas, extramedullary plasmacytomas occur as a result of hematogenous dissemination in various tissues and organs. Based on literature data, the incidence of bone plasmacytomas at multiple myeloma (MM) onset is 7.0 % to 32.5 %, and at relapsed/progression ММ stages it is 9.0 % to 27.4 %. During bone plasmacytoma development, tumor cells acquire a number of new features: expression of adhesion molecules is decreased, new cytogenetic aberrations occur, autocrine secretion and neoangiogenesis are increased. The clinical course of MM complicated by bone plasmacytomas is characterized by minimal bone marrow damage, hemoglobin concentration within reference range, and decreased values of β2-microglobulin, paraprotein, calcium, and lactate dehydrogenase. Acute renal failure and immunoparesis are rare, early MM stages predominate. In literature, the MM form with multiple bone plasmacytomas is referred to as ‘macrofocal MM’. Survival rates of MM patients with bone plasmacytomas are at the intermediate level in terms of prognosis. The MM patients without plasmacytomas have the most favorable prognosis, whereas the MM patients with extramedullary plasmacytomas have the poorest prognosis. There is no unified approach to the treatment of MM complicated by bone plasmacytomas. There are no randomized prospective clinical studies on the efficacy of treating it. A successful use of proteasome inhibitors and immunomodulatory drugs was reported based on a small number of MM cases with plasmacytomas. Some studies proved the efficacy of auto-HSCT in this MM form. Bone plasmacytomas are treated with radiotherapy mainly after systemic chemotherapy.