Comparative efficacy of tandem autologous versus autologous followed by allogeneic hematopoietic cell transplantation in patients with newly diagnosed multiple myeloma: a systematic review and meta-analysis of randomized controlled trials

Background: Despite advances in understanding of clinical, genetic, and molecular aspects of multiple myeloma (MM) and availability of more effective therapies, MM remains incurable. The autologous-allogeneic (auto-allo) hematopoietic cell transplantation (HCT) strategy is based on combining cytoreduction from high dose (chemo or chemoradio)-therapy with adoptive immunotherapy. However, conflicting results have been reported when an auto-allo HCT approach is compared to tandem autologous (auto-auto) HCT. A previously published meta-analysis has been reported; however, it suffers from serious methodological flaws. Methods: A systematic search identified 152 publications, of which five studies (enrolling 1538 patients) met inclusion criteria. All studies eligible for inclusion utilized biologic randomization. Results: Assessing response rates by achievement of at least a very good partial response did not differ among the treatment arms [risk ratio (RR) (95% CI) = 0.97 (0.87-1.09), p = 0.66]; but complete remission was higher in the auto-allo HCT arm [RR = 1.65 (1.25-2.19), p = 0.0005]. Event-free survival did not differ between auto-allo HCT group versus auto-auto HCT group using per-protocol analysis [hazard ratio (HR) = 0.78 (0.58-1.05)), p = 0.11] or using intention-to-treat analysis [HR = 0.83 (0.60-1.15), p = 0.26]. Overall survival (OS) did not differ among these treatment arms whether analyzed on per-protocol [HR = 0.88 (0.33-2.35), p = 0.79], or by intention-to-treat [HR = 0.80 (0.48-1.32), p = 0.39] analysis. Non-relapse mortality (NRM) was significantly worse with auto-allo HCT [RR (95% CI) = 3.55 (2.17-5.80), p < 0.00001]. Conclusion: Despite higher complete remission rates, there is no improvement in OS with auto-allo HCT; but this approach results in higher NRM in patients with newly diagnosed MM. At present, totality of evidence suggests that an auto-allo HCT approach for patients with newly diagnosed myeloma should not be offered outside the setting of a clinical trial.