Multiple Myeloma with Advanced Bone Disease and Low Tumor Burden - Different Clinical Presentation but Similar Outcome after Bortezomib-Based Therapy and Radiotherapy.

There is a small but well recognized group of patients with multiple myeloma (MM), characterized by multiple bone lesions and low tumor burden, the so-called macrofocal form of MM (MF-MM). The aim of the study was to analyze the incidence, clinical manifestation, therapeutic outcome and prognosis of patients with MF-MM treated with bortezomib-based therapy and radiotherapy, in comparison to classic MM. There were 148 MM patients treated with bortezomibbased regimens, with 15 (10.1%) of them meeting the criteria for MF-MM. Comparative analysis involved disease- and therapy-related variables and markers of bone metabolism in MF-MM and classic MM groups. Event-free survival (EFS) and median survival (MS) were analyzed. Patients in MF-MM and classic MM groups had similar mean age and sex distribution. Patients with MF-MM had advanced myeloma bone disease (MBD), significantly lower clonal plasma cell infiltration in bone marrow, and lower paraprotein level. These patients were predominantly in an early International Staging System stage, showed non-secretory and light-chain variants, and significant association with extramedullary plasmacytomas. EFS was 20 months in MF-MM group versus 13 months in classic MM group (nonsignificant difference). MS was 42 months in both MF-MM and classic MM groups. MF-MM presents with imbalance of the minimal tumor burden and massive bone involvement. Along with advanced skeletal manifestations, these patients showed features of preserved bone marrow and no end-organ damages. Following bortezomib-based therapy and radiotherapy, the EFS and MS did not differ between MF-MM and classic MM groups.