Patients with extramedullary manifestation of multiple myeloma: Prognostic factors and survival.

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e18552 Background: Multiple myeloma is a plasma cell dyscrasia that primarily involves bone marrow but also occurs in the soft tissues. While observing striking differences in clinical courses of patients with extramedullary plasmacytoma (EMP), solitary bone plasmacytoma (SBP), multifocal form of multiple myeloma (MFM) and multiple myeloma (MM), we wanted to assess prognostic factors and outcomes in those groups. This retrospective analysis was performed to evaluate response rate and overall survival (OS) of patients with extramedullary manifestations. Methods: We evaluated the data from 54 patients with MM (n=17), MFM (n=19), EMP (n=12) and SBP (n=6) treated at our institution from 1994-2012 and initially selected based on provided tissue samples. The MM control cohort was matched with regard to age, gender and prior treatment regimens. In 3 of 19 cases of MFM extramedullary locations were found at initial diagnosis. Two patients with EMP converted into MFM during the treatment. All EMP lesions arised in the upper aerodigestive tract. However extramedullary involvement in MFM was found in the head and neck (37%), chest (53%), abdomen (21%) and extremities (31%). Results: The 5-year OS rate was 92% in the patients with EMP. Whereas, 5-year OS rates of MM patients achieved 70.6%. MFM patients reached only 58% 5-year OS. The 5-year probability of progression was significantly higher in the group with MFM than EMP (89.5% vs 33%, p=0.0076, log rank test). Median progression free survival was 34 months for MM and 20 months for MFM (p=0.18). Conclusions: The 5-year progression free survival could be reached in 10 out of 12 patients with EMP. Two of the patients with primary EMP developed MFM. Moreover, the secondary development of extramedullary manifestation was associated with worse prognosis. Since the differences in the disease development cannot be easily predicted, there is an need of additional predictors that take into account different genetically determined risk status. Our retrospective analysis of genetic variations in this cohort of patients indicates the need of additional predictors in future randomized studies in these rare subtypes of MM.