Autologous-allogeneic versus autologous tandem stem cell transplantation and maintenance therapy with thalidomide for multiple myeloma patients under 60 years of age: a prospective, phase II study.

The role of autologous-allogeneic tandem stem cell transplantation (alloTSCT) followed by maintenance as upfront treatment for multiple myeloma is controversial. Between 2008 and 2014 a total of 217 multiple myeloma patients with a median age of 51 years were included by 20 German centers within an open-label, parallel-group, multicenter clinical trial to compare alloTSCT to autologous tandem transplantation (autoTSCT) followed by 2 years of maintenance therapy with thalidomide (100 mg/day) in both arms with respect to relapse/progression-free survival (PFS) and other relevant outcomes. A total of 178 patients underwent a second transplant (132 allogeneic, 46 autologous). PFS at 4 years after the second transplant was 47% (95% CI: 38-55%) for alloTSCT and 35% (95% CI: 21-49%) for autoTSCT (P=0.26). This difference increased to 22% at 8 years (P=0.10). The cumulative incidences of non-relapse mortality and of relapse at 4 years were 13% (95% CI: 8-20%) and 2% (95% CI: 0.3-2%) (P=0.044) and 40% (95% CI: 33-50%) and 63% (95% CI: 50-79%) (P=0.04) for alloTSCT and autoTSCT, respectively. The difference for relapse/progression increased to 33% (alloTSCT: 44%, autoTSCT: 77%) at a median follow-up of 82 months (P=0.002). Four-year overall survival was 66% (95% CI: 57-73%) for alloTSCT and 66% (95% CI: 50-78%) for autoTSCT (P=0.91) and 8-year overall survival was 52% and 50% (P=0.87), respectively. In conclusion, alloTSCT followed by thalidomide maintenance reduced the rate of recurrence or progression during a follow-up period of up to 10 years but failed to improve PFS significantly. This study was registered with ClinicalTrials.gov (NCT00777998).