Impact Of Proteasome Inhibitor Vs. Imid Maintenance Therapy On Outcomes Of Patients With High-Risk Multiple Myeloma (Hrmm).

e20557 Background: The ideal choice of maintenance therapy in patients with HRMM high-risk multiple myeloma remains unknown. We analyzed the outcomes of patients with HRMM undergoing transplant receiving different maintenance approaches. Methods: Patients with MM undergoing their first ASCT from 2012-19 within 1 year of diagnosis were identified from the prospectively maintained database of patients undergoing ASCT. HRMM was defined as having t(4;14), t(14;16), t(14;20), del17p13, or gain 1q detected on fluorescent in situ hybridization (FISH). Results: Of the 412 patients undergoing ASCT within 1 year of diagnosis, 333 had FISH data available and of these, 37% (124/333) patients had high-risk cytogenetics. Distribution of HR cytogenetics was as follows: deletion 17p: 37% (n = 46), t(4;14): 27% (n = 34), t(14;16) or t(14;20): 12% (n = 26), gain1q: 31% (n = 41). 9% (n = 12) had more than one HR abnormality. In patients with HRMM, median age at transplant was 59 years (range: 39 to 73), and 61% (n = 103) were males. 64% (n = 107) of high-risk patients received post-transplant maintenance therapy. Maintenance therapy in this group included a proteasome inhibitor (PI) in 34% (n = 29), immunomodulatory drug (IMiD) in 59% (n = 51), or both in 7% (n = 6). There was no difference in baseline characteristics of HRMM patients receiving PI vs. IMiD maintenance, except that patients with del17p were more likely to receive PI maintenance therapy (55% vs 28%, p = 0.01). (Table) After a median follow-up of 3.1 years from diagnosis, patients with HRMM had inferior PFS compared to patients with standard risk disease, with median PFS of 3 vs. 4.8 years, p < 0.001. Amongst the 86 HRMM patients receiving maintenance therapy, median PFS in patients receiving PI vs. IMiD vs. both PI + IMiD maintenance was 3 vs. 3.2 vs. 2.2 years, respectively, log-rank p = 0.7. In the sub-group of patients with 17p deletion, median PFS in the three groups was 3 vs. 2.9 vs. 2.2 years, respectively, log-rank p = 0.7. Conclusions: Patients with HRMM have inferior PFS compared to patients with standard risk disease. We observed similar outcomes in HRMM patients post-transplant regardless of the choice of maintenance therapy. [Table: see text]