Superior Complete Response Rate (CR) and Progression-Free Survival (PFS) with Bortezomib-Thalidomide-Dexamethasone (VTD) Versus Thalidomide-Dexamethasone (TD) As Consolidation Therapy After Autologous Stem-Cell Transplantation (ASCT) in Multiple Myeloma (MM)

In a randomized phase 3 study, the use of VTD as induction therapy prior to and consolidation therapy following double ASCT increased the rate of complete or near complete response (CR/nCR) and extended PFS in comparison with TD given as induction and post-ASCT consolidation therapy in 474 newly diagnosed MM patients (Cavo et al, Lancet 2010). However, the specific impact of VTD consolidation on improved clinical outcomes was not defined.

To address this issue, we performed a per-protocol analysis of 321 patients who received the entire treatment program, including the two pre-planned cycles of consolidation therapy with either VTD (160 of 236 patients, 68%) or TD (161 of 238 patients, 68%). By study design, two 35-d cycles of VTD (V 1.3 mg/m² on days 1, 8, 15, and 22; T 100 mg/d on days 1–35; D 40 mg on the days of and after each V administration) or TD (at the same doses as in VTD) were given as consolidation therapy to patients randomly assigned to each of the two respective induction regimens. Patient and disease characteristics at baseline were comparable in the two groups of patients.

The rates of CR and CR/nCR were significantly higher after consolidation therapy with VTD compared with TD (CR: 61% vs 47%; p=0.012; CR/nCR: 73% vs 61%; p=0.020). The impact of VTD consolidation on post-ASCT enhanced rates of CR and CR/nCR was confirmed by the McNemar test (CR: p=0.0009; CR/nCR: p=0.004) which conversely failed to demonstrate a significant increase in the frequencies of CR (p=0.052) and CR/nCR (p=0.110) with TD consolidation therapy. The absolute probability of upgrading from less than CR before consolidation to CR after consolidation was 31% with VTD and 17% with TD (Pearson chi-square test: p=0.03). Ninety six percent of patients who upgraded from less than CR to CR after VTD consolidation were in nCR (44%) or VGPR (52%) before starting consolidation therapy. A landmark analysis (with the landmark set as the start of consolidation therapy) was performed to compare time to progression (TTP), PFS, and overall survival (OS) between treatment groups. With a median follow-up of 30 months, the estimated 3-year probability of relapse or progression was 38% with VTD and 52% with TD (p=0.039 by Kaplan-Meier analysis) (HR: 0.68, 95% CI: 0.47–0.98, p=0.041). PFS was significantly longer for patients receiving VTD consolidation than for those treated with TD (3-year estimates: 62% vs 46%; p=0.025) (HR: 0.66, 95% CI: 0.46–0.95, p=0.027), a gain particularly evident for patients who failed to achieve CR after ASCT (3-year PFS estimates: 66% vs 43%; HR: 0.54, 95% CI: 0.32–0.91, p=0.022). Superior PFS with VTD vs TD consolidation was retained across poor prognosis subgroups, including patients with t(4;14) and/or del(17q) (HR: 0.44, p=0.004), del(13q) (HR: 0.44, p=0.002), β₂-microglobulin >3.5 mg/L (HR: 0.57, p=0.025), lactate dehydrogenase >190 U/L (HR: 0.57, p=0.005), or ISS stage 2 and 3 (HR: 0.57, p=0.021). In a multivariate regression analysis, the most important and independent variables positively correlated with PFS were VTD consolidation therapy (p=0.002), double ASCT (p=0.001), low β₂-microglobulin (p<0.0001), and absence of t(4;14) and/or del(17q) (p<0.0001). No OS difference was seen between the two groups. Both VTD and TD consolidation therapy were very well tolerated. The frequency of treatment-emergent grade 3–4 adverse events was comparable in the two groups (9.3% in VTD, 8.6% in TD). Of particular note, peripheral neuropathy was 0.6% with VTD, while the rates of skin rash and deep vein thrombosis were 0.6% in each of the two groups. Patients treated with VTD received 93% of planned doses of bortezomib and thalidomide.

In comparison with TD, post-ASCT consolidation therapy with the triplet VTD regimen significantly increased the rates of CR and CR/nCR, and extended landmarked TTP and PFS. Superior PFS with VTD consolidation was maintained across poor prognosis subgroups, including those with advanced ISS stage and/or high-risk cytogenetic profiles. In a multivariate regression analysis VTD consolidation was confirmed to be an independent variable favorably affecting PFS. The superior activity seen with VTD versus TD as induction therapy before ASCT was retained despite the same triplet regimen being used as post-ASCT consolidation.

Cavo:Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria; Genzyme: Honoraria. Off Label Use: Bortezomib and Thalidomide as post autotransplantation consolidation therapy in myeloma. Patriarca:Schering-Plough: Honoraria; Celgene: Honoraria; Janssen: Honoraria; Roche: Honoraria. Petrucci:Celgene: Honoraria; Janssen: Honoraria. Di Raimondo:Janssen: Honoraria, Speakers Bureau; Celgene: Honoraria, Speakers Bureau. Palumbo:Merck: Honoraria; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria. Offidani:Celgene: Honoraria; Janssen: Honoraria. Baccarani:Bristol-Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.