Tandem Autologous Stem Cell Transplantation Does Not Benefit High-Risk Myeloma Patients In The Maintenance Era: Real-world Results From The Canadian Myeloma Research Group Database

Abstract

Background: In patients with multiple myeloma, the presence of high-risk cytogenetic abnormalities is associated with worse disease control and survival. Autologous stem cell transplant does benefit these patients. Tandem transplantation has been explored as a means to deepen responses and further improve survival however, its role remains controversial. This is particularly true in the era of novel agent induction and post-transplant maintenance therapy. Objectives: The aim of this study was to use the Canadian Myeloma Research Group database (CMRG-DB) and examine a large cohort of real-world patients comparing the outcomes of tandem versus single ASCT specifically in high-risk patients receiving novel agent-based induction and post-transplant maintenance. Study Design: The data for this study was derived retrospectively from a comprehensive national-level database of Canadian patients with multiple myeloma. High-risk cytogenetics were defined as presence of del17p, t(4;14) or t(14;16). Those receiving allogeneic transplant were excluded. Tandem transplantation was defined as a second ASCT performed consecutively without interim relapse or progression after first ASCT. Those with relapse or progressive disease within three months of completing a first transplant were excluded. We compared response depth, progression free and overall survival based on single or tandem transplantation procedures. The impact of covariates of interest was also assessed. Results: 381 patients with high-risk cytogenetics were identified. 242 received single and 139 patients received tandem transplants. All received post-transplant maintenance. The most common induction regimen for these patients was cyclophosphamide, bortezomib, and steroids (CyBorD, 87%). Forty-one patients (10.8%) required reinduction prior to first ASCT. The best overall responses at any time were 98.3% (90.5% ≥ VGPR) and 98.6% (89.9% ≥ VGPR) in the single and tandem ASCT groups respectively. Survival outcomes were similar with the median PFS for single or tandem ASCT of 35.2 and 35.3 months (p=0.88) and the median OS were 92.6 and 88.9 months respectively (p=0.72). No statistically significant differences were seen based on type of cytogenetic abnormality or type of maintenance. This was confirmed on multivariate analysis. Conclusion: In the real-world setting, tandem ASCT does not improve outcomes for MM patients with high-risk cytogenetics. This may be driven by the use of effective pre- and post-ASCT therapies. The development of more potent induction and consolidation along with current nearly ubiquitous continuous maintenance therapies until disease progression does not support the use of a second high dose procedure.