Intensification Therapy with Bortezomib-Melphalan-Prednisone Versus Autologous Stem Cell Transplantation for Newly Diagnosed Multiple Myeloma: An Intergroup, Multicenter, Phase III Study of the European Myeloma Network (EMN02/HO95 MM Trial)

Background

The role of upfront autologous stem cell transplantation (ASCT) for younger patients with newly diagnosed (ND) multiple myeloma (MM) has been questioned in the novel agent era.

Methods

A prospective, multicenter, phase III study was designed to compare (first randomization, R1) (1:1 ratio; stratification according to ISS stage) four 42-day cycles of bortezomib-melphalan-prednisone (VMP) given at the same dosing schedule reported in the VISTA study (NEJM 2008; 359:906-17) vs either a single course or two sequential courses of melphalan at 200 mg/m² (HDM) followed by single or double ASCT, respectively, as intensification therapy after three to four 21-day cycles of induction therapy with bortezomib-cyclophosphamide-dexamethasone and subsequent collection of peripheral blood stem cells. A second randomization (R2) to consolidation therapy with bortezomib-lenalidomide-dexamethasone vs no consolidation was performed after intensification, to be followed by lenalidomide maintenance until progression or toxicity in both arms. A primary study end point was progression-free survival (PFS) from R1.

Results

From February 2011 to April 2014, 1510 patients aged ≤65 years with symptomatic NDMM were registered. Of these, 1192 were eligible for R1 and were randomly assigned to receive either VMP (n=497 patients) or HDM (1±2 courses) (n=695 patients). Median age was 58 years in both groups, ISS stage III was 21% in VMP and 20% in HDM, while revised ISS stage III was 9% in both groups. Data on cytogenetic abnormalities, as detected by FISH analysis of CD138+ plasma cells, were available in 71% of patients (n=354) randomized to VMP and in 76% of those (n=529) assigned to HDM. The frequency of conventionally defined high-risk cytogenetic changes, including t(4;14) and/or del(17p) and/or t(14;16), was 25% in both arms. Median follow-up from R1 was 26 (IQR: 19-37) months. On an intention-to-treat basis, median PFS was 44 months in the VMP arm and was not yet reached in the HDM arm; 3-year estimates of PFS were 57.5% and 66%, respectively (HR=0.73; 95% CI=0.59-0.90; P=0.003). PFS benefit with HDM was retained across predefined subgroups, including patients with ISS stage I (HR=0.69; CI=0.48-0.98; P=0.037), revised ISS stage II (HR=0.70; CI=0.54-0.91; P=0.008), revised ISS stage III (HR=0.54; CI=0.30-0.97; P=0.040), standard-risk cytogenetics (HR=0.75, CI=0.56-1.01; P=0.055) and a high-risk cytogenetic profile (HR=0.54; CI=0.37-0.80; P=0.002). The probability of achieving a very good partial response or higher quality response was 85.5% in the HDM group vs 74% in the VMP group (odds ratio=1.90; CI=1.42-2.54; P<0.001). In a multivariate Cox regression analysis stratified by ISS, randomization to HDM (HR=0.67; CI=0.53-0.85; P=0.001) and absence of high-risk cytogenetic abnormalities (0.71; CI=0.53-0.95; P=0.021) were the leading independent predictors of prolonged PFS. Overall survival was not yet mature and no difference between the two treatment groups was evident. Detection of minimal residual disease (MRD) after intensification therapy was performed by multiparameter flow cytometry and PET/CT in a subgroup of patients, and details are provided in a separate abstract (E. Zamagni et al). Overall, MRD negativity favorably affected PFS and OS.

Conclusions

In comparison with VMP as standard-dose intensification therapy, upfront HDM and ASCT significantly improved PFS and increased the rate of high quality responses. An updated analysis with a longer follow-up will be reported at the meeting. Results of this phase III study, the largest so far reported, support the conclusion that upfront ASCT still continues to be the reference treatment for fit patients with NDMM, even in the novel agent era.