The Role of Salvage Autologous Stem Cell Transplantation in Relapsed Multiple Myeloma-a Single Center Experience at Umc Ljubljana

Background

In the era of novel agents, the role of salvage autologous stem cell transplantation (ASCT) for treating relapsed multiple myeloma (MM) remains uncertain due to insufficient efficacy data. The decision to proceed with ASCT depends on several factors, with the most decisive criterion being the time to relapse following the previous ASCT. It is considered for patients on maintenance therapy who have been in remission for more than 36 months, and for those not receiving maintenance therapy who have been in remission for more than 24 months. Despite numerous studies in relapsed MM, only one prospective randomized trial directly compared salvage ASCT with continuous treatment using novel agents.

Patients and methods

We retrospectively analyzed all patients from our institutional registry treated with salvage ASCT for relapsed MM between April 2008 and October 2023. The primary endpoint was progression-free survival (PFS) from salvage ASCT, with secondary endpoints being overall survival (OS) from ASCT and overall response rates (ORR) on day +100 from salvage ASCT.

Results

A total of 78 patients underwent salvage ASCT, with a median follow up (FU) from diagnosis and from salvage ASCT to relapse being 87.5 months and 29 months respectively. Median age was 62 years (range, 48-78), with male to female ratio 2:1. The median time from first ASCT to salvage ASCT was 46 months (range, 21-163). The median number of previous lines of therapies was 2 with 26 % of patients receiving ≥3 lines of therapy before salvage ASCT. The majority of patients (81%) received reinduction therapy before salvage ASCT. The median PFS and OS from salvage ASCT was 24 months and 76 months. The ORR following ASCT was 82% with 63% achieving at least a very good partial response (VGPR). There were no statistically significant differences observed in PFS or OS between groups based on standard vs. high-risk cytogenetics (PFS at 36 months FU 36% vs. 24%), age below or above 60 years (PFS at 36 months FU 28.6 vs 31%), or the number of prior lines of treatment (<3 vs. ≥3) (PFS at 36 months FU 29.8 vs 28.6%). Duration of remission following first ASCT did not influence PFS or OS following salvage ASCT (remission <36 vs ≥ 36 months; PFS 23 vs 24 months).

Conclusions

Despite the emergence of new treatment options such as immune cell therapies, our retrospective data analysis supports the use of salvage ASCT in selected patients. Our patient population considered for salvage ASCT included mainly younger patients with a long remission following the first ASCT. This might be the main reason no statistically significant differences were found based on age, cytogenetics and number of prior treatments. In settings of limited availability of CAR-T cell therapy and financial burden of both CAR-T cell and bispecific antibodies in low income countries, ASCT remains a viable option for treatment of relapse MM for selected patients. Further randomized studies are needed to compare the efficacy of salvage ASCT to CAR-T therapy or the sequencing of these treatment options.

No relevant conflicts of interest to declare.