Outcomes after delayed and second autologous stem cell transplant in patients with relapsed multiple myeloma.

We evaluated the outcomes of 168 patients undergoing delayed or second autologous stem cell transplant (ASCT) for relapsed multiple myeloma (MM) from 2010 to 2019. Overall, 21% (n = 35) patients had received a prior transplant and 69% (n = 116) underwent transplant at first relapse. Overall, 27% patients had high-risk cytogenetics and 15% had ISS stage III disease. Stem cell collection was performed after relapse in 72% and 35% of patients received maintenance therapy. Median PFS from salvage treatment and transplant were 28 and 19 months, respectively. Median OS from salvage treatment and transplant was 69 and 55 months. Multivariate analysis revealed that ASCT in first relapse was associated with superior PFS (HR 0.63, p = 0.03) and OS (HR 0.59, p = 0.04) compared to later lines of therapy. In addition, PFS of ≥36 months with prior therapy was associated with improved PFS (HR 0.62, p = 0.04) and OS (HR 0.41, p = 0.01). Ninety-five patients underwent delayed transplant at first relapse, median PFS and OS from start of therapy was 30 and 69 months, and median OS from diagnosis was 106 months. These data may serve as a guide when counseling patients undergoing ASCT for relapsed MM and provide a benchmark in designing clinical trials of transplantation/comparative treatments for relapsed MM.