Outcomes of young adults (aged ≤ 40 years) with newly diagnosed multiple myeloma after up-front autologous stem cell transplant.

Multiple myeloma (MM) primarily affects older patients. There are scarce data on the outcomes of young adults undergoing autologous transplantation (auto-HCT). In this single-centre analysis, we included 117 younger patients, with a median age of 37 years (range 22-40) at transplant. Seventeen (15%) patients had high-risk cytogenetics. Before transplant, 10% of patients achieved ≥CR and 44% achieved ≥VGPR. At best post-transplant response, 56% and 77% of patients achieved ≥CR and ≥VGPR respectively. With a median follow-up for survivors of 72.6 months (range 0.9-238.0), median PFS and OS were 43.1 months (95% CI 31.2-65.0) and 146.6 months (95% CI 100.0-208.1) respectively. Patients who underwent auto-HCT after 2010 had better median PFS (84.9 months vs. 28.2 months, p < 0.001) and OS (NR vs. 91.8 months, p < 0.001) compared with those transplanted earlier. In multi-variate analysis, achieving ≥CR as best post-transplant response was associated with improved PFS (HR [95% CI] 0.55 [0.32-0.95], p = 0.032), while achieving ≥VGPR was predictive of superior OS (0.32 [0.16-0.62], p < 0.001). Three patients (3%) developed a second primary malignancy. Younger MM patients had durable survival after auto-HCT, which further improved after the availability of novel anti-myeloma drugs in recent years. Depth of response following transplant remains a key predictor of survival.