As part of the overall STAMiNA trial, they were randomized to single autologous hematopoietic cell transplantation (HCT); autologous HCT followed by a second autologous HCT (tandem autologous HCT); or single autologous HCT followed by four cycles of consolidation with lenalidomide, bortezomib, and dexamethasone (RVD). All three arms continued on lenalidomide maintenance after those interventions.
Overall results of the STAMiNA trial, previously reported, showed no significant differences in progression-free survival or overall survival among the three transplant strategies (J Clin Oncol. 2019 Jan 17. doi: 10.1200/JCO.18.00685).
In this PRIMeR substudy, by contrast, progression-free survival was significantly increased for patients who were MRD negative at all three time points measured, Dr. Hahn reported, while overall survival was significantly improved based on MRD status measured at the 1-year time point.
The rate of MRD negativity did not differ significantly between arms at baseline or premaintenance time points, Dr. Hahn said. Those rates were 42%, 47%, and 40%, respectively, for the single transplant, tandem transplant, and single transplant plus consolidation arms, while the premaintenance MRD negativity rates were 77%, 83%, and 76%.
At 1 year, MRD negativity rates were significantly different between arms, but only in the intent-to-treat analysis.
Most of the difference was due to an increased rate of MRD negativity in the tandem-transplant arm, compared to a single auto-transplant. However, about 30% of patients in the tandem transplant arm did not receive the therapy, so in the analysis by actual treatment received, the rates of MRD negativity were 81% for single transplant, 90% for tandem transplant, and 85% for single transplant plus consolidation (P = 0.2).