Real-World Outcomes of Upfront Autologous Hematopoietic Stem Cell Transplantation in Patients With Newly Diagnosed Multiple Myeloma With Deletion 17p

Despite tremendous advancements in multiple myeloma (MM) therapeutics, outcomes remain heterogeneous, heavily influenced by clinical and cytogenetic factors. Among these, deletion of the short arm of chromosome 17 (del(17p)) is a strong predictor of poor prognosis. The aim of this study was to evaluate real-world outcomes in patients with newly diagnosed MM (NDMM) with del(17p) undergoing upfront autologous hematopoietic stem cell transplantation (auto-HCT). We conducted a single-center retrospective analysis of patients with NDMM who underwent upfront auto-HCT at MD Anderson Cancer Center between 2008 and 2018. Primary endpoints were progression-free survival (PFS) and overall survival (OS), with secondary endpoints being hematological response and measurable residual disease (MRD) status postauto-HCT. MRD status in the bone marrow biopsy was evaluated using 8-color next-generation flow cytometry with a sensitivity of 1/10^-5 cells. One hundred and fifteen patients were included (55% male). Median age at auto-HCT was 62 years (range 34 to 83). The median del(17p) clone size was 20%, with 51 (53%) patients having clone sizes >20% and 15 (15%) patients having clone sizes >55%. Additional high-risk cytogenetic abnormalities included t(4;14) in 15 (13%) patients, t(14;16) in 8 (7%) patients, and 1q21+ in 25 (22%) patients. After induction, 10% of patients achieved ≥ CR, and 50% achieved ≥ VGPR, with 25% having MRD-negative ≥ VGPR. Post-transplant, 42% achieved ≥ CR, and 83% achieved ≥ VGPR as best response, with 55% (48/87) having MRD-negative ≥ VGPR. With a median follow-up of 31.4 months (range 3.1 to 199.1), median PFS and OS for the entire cohort were 19.9 and 71.5 months, respectively, and 5-year OS was 53%. Concurrent del(17p) and t(4;14) were associated with significantly worse outcomes, with median PFS and OS of 11.5 and 22.4 months, respectively. In multivariable analysis (MVA), female sex was associated with worse PFS (HR [95% CI] 2.87 [1.75 to 4.72], P < .001), while MRD negative CR post-transplant (0.35 [0.18 to 0.68], P = .002) and maintenance therapy (0.46 [0.27 to 0.77], P = 0.003) were associated with better PFS. In MVA for OS, female sex (2.22 [1.18 to 4.17], P = 0.013) and the presence of t(4;14) (2.55 [1.09 to 5.95], P = 0.030) were associated with worse OS, whereas Karnofsky Performance Status of ≥90 (0.47 [0.23 to 0.94], P = 0.034) was associated with better OS. This study affirms del(17p) as a high-risk abnormality with unfavorable outcomes despite modern therapies. The co-occurrence of del(17p) and t(4;14) was associated with particularly poor outcomes. Novel approaches are needed for this high-risk subgroup.