P26: EXTRAMEDULLARY MULTIPLE MYELOMA: A MONOCENTRIC RETROSPECTIVE OBSERVATIONAL STUDY
Authors: M Brescini, F Fazio, MT Petrucci
Journal: HemaSphere (2022)

Extramedullary Multiple Myeloma (EMM) is a distinctive sub-entity of Multiple Myeloma, characterized by clonal plasma-cells proliferation outside the bone marrow; it can be diagnosed either as a tissue growing in contiguity with bone marrow (paraskeletal) or in distant organs (extramedullary). This subset of patients, especially the latter ones, have a poor prognosis, and there are not EMM-specific therapy schedules. The aim of our observational study was to describe patients that presented both type of EMM in order to report which common therapeutic approaches were used and to identify which disease characteristics mostly affected overall survival. We retrospectively analyzed 111 patients (pts) with EMM disease referred to the Hematology Department of Sapienza University of Rome between 2004 and 2021: 64 presented EMM at the onset of disease and 37 at relapse. Sixty-one pts were male and 50 were female (55% vs 45%); 60 pts (54.1%) were ISS-1 and the most common isotype was IgG (62.2%), followed by IgA (22.5%) and light chain myeloma (11.7%). Cytogenetics data were available for 37 patients: among them, 8 patients showed a high-risk cytogenetics profile: the most frequent findings were del13q (40.5%), amp/gain1q (24.3%) and t(4;14) (13.5%). Out of these 37 pts, 11 (30%) presented 2 or more cytogenetics alterations, while 4 pts (11%) presented a complex karyotype. Ninety-eight pts (88%) presented a paraskeletal localization, while 13 pts (12%) showed extramedullary localizations; the most frequent organs involved were soft tissues (5/13), followed by nervous central system, lymph nodes and orbit (2/13). Regarding the therapeutic approaches, 47% of pts with EMM at diagnosis received regimens containing a proteasome inhibitor (PI) and immunomodulatory drugs (IMiDs); 38% of pts underwent autologous stem cell transplantation (ASCT). At relapse, the most used regimens (30% of pts) were combinations containing monoclonal antibodies or IMiDs monotherapy. In both groups, one-third of patients underwent radiotherapy to reduce the local symptoms. After a median follow-up of 52 months for pts with EMM at diagnosis and 20 months for pts at relapse, the median OS was 147 months (mo) in first group and 32 mo in the second group (p<0.001). Among pts with EMM at diagnosis, pts who underwent ASCT showed a better median OS compared to other pts (NR vs 87.6 mo, p=0.004). Analyzing the type of EMM, we showed that pts with an extramedullary localization had a worse outcome compared to pts with paraskeletal disease (median OS 43.4 vs 147 months, p=0.011). Despite the limit of our cohort, pts with EMM at diagnosis and high-risk cytogenetics had a worse outcome compared to those with standard-risk cytogenetics (median OS: 33.2 months vs NR, p=0.041). Multivariate analysis showed that the ASCT and obtaining at least a very good partial response after therapy were independent factors associated with better progression free survival (PFS). Regarding OS, obtaining at least a partial response and a previous therapy with a PI were independent factors associated with better OS. Despite the limits of the retrospective study, our data demonstrated that specific therapy based on PIs and ASCT could overcome the poor prognostic factor of EMM, according to the previous published data. Further studies are warranted to assess the optimal strategies for pts with extramedullary EMM, whose prognosis is still poor.