Is Tandem ASCT Needed in MM Patients with High Risk Cytogenetics in the Era of Maintenance Therapy? Results from the Canadian Myeloma Research Group (CMRG) Database

Background: Recent studies evaluating tandem autologous transplantation for multiple myeloma (MM) show conflicting results in terms of efficacy. However subgroup analysis suggests that those with high-risk disease may benefit the most from tandem transplant. We used the CMRG database to compare single versus tandem ASCT for patients with MM with high-risk cytogenetics. Methods: The primary objective was to compare PFS in MM patients with high-risk cytogenetics (p53 deletion, t(4;14), t(14;16)) identified from the CMRG database undergoing front-line single or tandem ASCT from 01/2010 to 06/2019. Secondary objectives compared OS, ORR, and outcomes based on whether post-transplant maintenance was given. OS and PFS rates were calculated from the date of first ASCT using the Kaplan-Meier method. ORR was assessed by Chi-square using best response post ASCT. Results: There were 302 single and 125 tandem transplants, followed by maintenance therapy in 190 (63%) and 96 (77%) respectively. Translocation (4;14) was seen in 209 (49%), t(14:16) in 61 (15.6%) and delP53 in 222 (52%) with more than one abnormality in 65 patients. The most common induction regimen consisted of cyclophosphamide, bortezomib, and steroids, (83%) followed by bortezomib and dexamethasone (8%) and dexamethasone alone (4.7%). Forty-seven patients (11%) required reinduction prior to first ASCT with regimens including RVD (49%), Rd (23%) and others (D/DT/VD-PACE, CyBor-D, KRD, VD, IxaRD, 28%). Maintenance was prescribed to 286 patients with regimens including lenalidomide ± dexamethasone (65%), lenalidomide + proteasome inhibitor ± dexamethasone (22%), proteasome inhibitor ± dexamethasone (11%) and others (2%). Patient characteristics are summarised in table 1. The overall response rate was 93.9% (94.5% for single ASCT and 92% for tandem ASCT). The PFS at 3 years was 41.1% (single) and 45.7% (tandem) with median PFS 26 vs 35 months respectively (p=0.0621). Three year OS was 71.5% (single) and 83.8% (tandem), median OS 83 vs 89 months (p=0.0060). Both PFS and OS were improved with the use of maintenance therapy, regardless of single vs tandem transplant. PFS at 3 years was 52.1% for those receiving maintenance therapy compared to 21.7% for no maintenance (median 42 vs 16 months, p