Bortezomib-Thalidomide-Dexamethasone Compared with Thalidomide-Dexamethasone as Induction and Consolidation Therapy Before and After Double Autologous Transplantation In Newly Diagnosed Multiple Myeloma: Results From a Randomized Phase 3 Study

Abstract 42

We prospectively compared thalidomide-dexamethasone (TD) with bortezomib-thalidomide-dexamethasone (VTD) as induction therapy before, and consolidation after, double autologous stem-cell transplantation (ASCT) in patients with newly diagnosed multiple myeloma (MM). Three 21-d cycles of either VTD (V, 1.3 mg/m² twice-weekly; T, 200 mg/d through d 1 to 63; D, 320 mg/cycle) or TD were given as induction therapy. Consolidation therapy comprised two 35-d cycles of VTD (V, 1.3 mg/m² once-weekly; T, 100 mg/d through d 1 to 70; D, 320 mg/cycle) or TD. 474 patients randomized to the VTD (n=236) or TD (n=238) arm were analyzed on an intention-to-treat basis for response rate, PFS and OS. Centrally reassessed CR/nCR rate was significantly higher in the VTD compared with the TD arm after all treatment phases, including induction therapy (30% vs 10%, p<0.0001), double autotransplantation (54% vs 42%, p=0.008) and consolidation therapy (60% vs 44%, p=0.001). Best confirmed overall CR/nCR rate was 71% in the VTD arm compared with 52% in the TD arm (p<0.0001); the corresponding values for VGPR or better were 89% vs 72%, respectively (p<0.0001). To evaluate the role of consolidation therapy we performed a per-protocol analysis of 323 patients, 161 treated with VTD and 162 with TD. Overall, upgraded responses with VTD and TD as consolidation therapy were observed in 55% vs 37% of patients, respectively (p=0.01; OR:1.15-3.77). Furthermore, the probability to improve responses from less than CR before consolidation to CR after consolidation was 28% with VTD vs 15% with TD (p=0.02; OR:1.07-4.57) (p=0.003 using the Mc Nemar's test). Post-consolidation molecular detection of minimal residual disease was the objective of a substudy; detailed results are reported in a separate abstract. Briefly, both qualitative and quantitative analyses confirmed the statistically significant superiority of VTD over TD in effecting higher rates of molecular remissions and reducing the burden of residual myeloma cells after ASCT. Any grade 3–4 non-hematologic adverse events were 10% with VTD (peripheral neuropathy: 1.3%, skin rash: 0.6%) vs 12% with TD. With a median follow-up of 31 months, median PFS was 42 months in the TD arm and was not yet reached in the VTD arm (44-month projected rate: 61%) (HR: 0.62 [CI: 0.45–0.87], p=0.006). Superior PFS in the VTD vs TD arm was retained across patient subgroups with poor prognosis, including those with t(4;14) and/or del(17p). Randomization to VTD overcome the adverse influence of t(4;14) on PFS (40-month projected rates: 69% vs 67% according to the presence or absence of this abnormality, respectively; p=0.6). By the opposite, in the TD arm corresponding median PFS values were 24.5 vs 41.5 months, respectively (p=0.01). The small numbers of patients with del(17p) in both arms of the study precluded a statistical comparison with del(17p)-negative group. In a multivariate analysis, variables favorably influencing PFS were beta2-m lower than 3.5 mg/L (HR:0.47; p=0.000), absence of t(4;14) and/or del(17p) (HR:0.52; p=0.000), randomization to VTD arm (HR:0.57; p=0.002), attainment of at least VGPR (HR:0.50; p=0.009) and CR (HR:0.8; p=0.01). No statistically significant difference between the overall treatment protocols was seen in terms of OS, although curves seemed to initially diverge after 40 months (44-month projected rates: 84% vs 74% for VTD and TD arms, respectively). A multivariate analysis showed the independent role of absence of t(4;14) and/or del(17p) (HR:0.42; p=0.003), ISS stage1-2 (HR:0.49; p=0.02) and randomization to VTD (HR:0.53; p=0.04) in prolonging OS. When time-dependent CR entered the model, absence of t(4;14) and/or del(17p) and less advanced ISS stage retained their positive prognostic value; attainment of CR (strictly related to VTD randomization) was an additional favorable variable. In conclusion, in comparison with the TD arm of the study, 1) VTD induction emerges as a new standard of care for maximizing the degree and speedy of tumor reduction in preparation for ASCT; 2) VTD consolidation effected significantly higher rates of upgraded responses, including CR, and of molecular remissions; 3) double ASCT incorporating VTD as induction and consolidation therapy resulted in significantly longer PFS, a benefit confirmed in a multivariate regression analysis and maintained in the subgroup of patients with adverse cytogenetic abnormalities.