Autologous followed by allogeneic versus tandem-autologous transplantation in high-risk, newly diagnosed multiple myeloma: a systematic review and meta-analysis

Objectives: High-risk multiple myeloma (HRMM) is associated with poor survival, despite many advances in antimyeloma strategies. Autologous followed by allogeneic stem cell transplantation (auto-allo-SCT) has yielded controversial results compared to tandem autologous stem cell transplantation (auto-SCT) in patients with HRMM. We conducted this meta-analysis to compare the efficacy and safety of auto-allo-SCT and tandem-auto-SCT in patients with HRMM.

Methods: Embase, Cochrane Library, and PubMed databases were searched until March 2023. Prospective or retrospective studies comparing the effects of auto-allo-SCT and tandem-auto-SCT were included. Hazard ratios (HRs) and 95% confidence intervals (CIs) for time-to-event outcomes, and odds ratios (ORs) and 95%CIs for dichotomous outcomes were pooled using random-effects models.

Results: Three studies involving 491 patients were included. Despite auto-allo-SCT seemed to be associated with improvements in progression-free survival (PFS) (HR [95%CI], 0.71 [0.51-1.00]) and complete response (CR) (OR [95%CI], 3.16 [1.67-5.99]), and reduced relapse/progression rates (47% vs. 55%) in comparison with tandem-auto-SCT, no marked improvement in overall survival (OS). In comparison to tandem-auto-SCT, patients assigned to auto-allo-SCT exhibited a higher risk of transplant-related mortality (TRM) (11.9% vs. 4.1%) and non-relapse mortality (NRM) (12.3% vs. 3.1%).

Conclusion: Auto-allo-SCT seemed to be associated with improvements in PFS and CR when compared to tandem-auto-SCT in patients with HRMM, but it did not lead to a significant improvement in OS. Furthermore, patients in the auto-allo-SCT group were at a higher risk of developing TRM and NRM. Auto-allo-SCT transplantation should not be routinely incorporated into HRMM therapy but rather should be considered investigational.