P934: the effects of extramedullary disease on outcomes of patients with newly diagnosed multiple myeloma

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: Extramedullary involvement (or extramedullary disease, EMD) represents an aggressive form of multiple myeloma (MM). Two types of EMDs are known to exist: extramedullary‐extraosseous (EM-E) and extramedullary‐bone related (EM-B). Although several new EMD treatments are available, the prognosis of MM patients with EMD remains poor. About 20% of newly diagnosed MM (NDMM) patients who had at least 1 site of extramedullary involvement and the impact on outcome of EMD in NDMM is influenced by different types of involvements. Whether EMD is an independent diagnosis factor at diagnosis needs to be further investigated. Aims: This study is aimed to summarize the newly diagnosed multiple myeloma (NDMM) patients in Ruijin Hospital affiliated to Shanghai Jiaotong University School of Medicine. We compared the clinical characteristics and prognosis among patients with non-EMD, bone-related extramedullary (EM-B) disease and extraosseous extramedullary (EM-E) disease, and further explored the effects of autologous hematopoietic stem cell transplantation (ASCT) on EMD. Methods: From January 2015 to January 2022, 114 patients with EMD out of 515 NDMM patients were retrospectively analyzed, accounting for 22%, with 91 (18%) patients in the EM-B group and 23 (4%) in the EM-E. Clinical characteristics of patients in three groups were compared by chi-square test. PFS and OS of those patients were analyzed by the Kaplan-Meier method. Independent prognostic factors were determined using multivariate analysis of Cox proportional hazard model. Results: There were no significant differences in age, gender, ISS stage, light chain, creatinine clearance, cytogenetic risk, 17p deletion, ASCT and induction regimens among the three groups. 13% of EM-E patients had IgD-type M protein, which was significantly higher (p=0.021). Median PFS of non-EMD, EM-B and EM-E was 27.4 months, 23.1 months and 14.0 months respectively, and median OS was not reached, 76.8 months and 25.6 months. PFS (vs. non-EMD, p=0.004; vs. EM-B, p=0.036) and OS (vs. non-EMD, p=0.000; vs. EM-B, p=0.002) were significantly worst for EM-E, while no significant difference in PFS and OS was observed between EM-B and non-EMD. In multivariate analysis, EM-E was an independent prognostic risk factor for OS in NDMM patients (HR=8.779, p=0.000), and had a negative impact on PFS (HR=1.874, p=0.05). EM-B patients had significantly worse OS than non-EMD (median 76.8 months vs. not reached, p=0.029) in non-ASCT patient populations. However, no significant difference was observed in PFS and OS between EM-B and non-EMD patients receiving ASCT. Summary/Conclusion: Compared to non-EMD and EM-B patients at diagnosis, EM-E showed the worst prognosis. EM-E was an independent risk factor for OS in NDMM patients. ASCT can overcome the poor prognosis of EM-B. Keywords: Diagnosis, Multiple myeloma, Autologous hematopoietic stem cell transplantation