Outcomes of patients with multiple myeloma undergoing autologous transplant with suboptimal pretransplant response.

There are scarce data in the literature focusing on newly diagnosed multiple myeloma (NDMM) patients who undergo autologous haematopoietic cell transplantation (autoHCT) after achieving suboptimal response to induction. To address this, we performed a retrospective, single-centre analysis of patients with NDMM who underwent upfront autoHCT between 2005 and 2021 with a pretransplant response of less than very good partial response (<VGPR). Primary outcomes were progression-free survival (PFS) and overall survival (OS). 1109 patients were included in our analysis. Median PFS and OS for the entire cohort were 38.6 (95% confidence interval [CI], 35.9-41.9) months and 103.8 (95% CI, 96.4-113.2) months, respectively. Patients with high-risk cytogenetic abnormalities (HRCA) had a median PFS and OS of 24.8 months and 69.9 months respectively. In multivariable analysis, the use of post-transplant maintenance (hazard ratio [HR] 0.75, p = 0.001 and HR 0.75, p = 0.008) and achieving complete response (CR) at best post-transplant response (HR 0.60, p < 0.001 and HR 0.51, p < 0.001) were associated with superior PFS and OS respectively. In conclusion, NDMM patients who received upfront autoHCT with a pretransplant response of <VGPR had a median PFS of >3 years and median OS of >8 years. Post-transplant maintenance further improved survival outcomes.