High-dose busulfan-melphalan vs melphalan and reinforced VRD for newly diagnosed multiple myeloma: a phase 3 GEM trial

In retrospective studies, autologous stem cell transplantation (ASCT) conditioning with intravenous busulfan and melphalan (BUMEL) led to longer progression-free survival (PFS) than melphalan alone (MEL200). We compared long-term outcomes of BUMEL vs MEL200 in the context of intensified bortezomib, lenalidomide, and dexamethasone (VRD) induction and consolidation therapies. GEM12 was a phase 3 trial for patients with newly diagnosed multiple myeloma (NDMM) eligible for ASCT including 6 reinforced VRD cycles followed by ASCT conditioned with BUMEL or MEL200 and 2 VRD consolidation cycles. The primary end point was PFS. Subgroup analyses were based on International Staging System (ISS) stages and high-risk genetic abnormalities. Patients were randomized with an open-label 2 × 2 factorial design and 1:1:1:1 allocation ratio to ensure the balance between the GEM12 and the subsequent phase 3 GEM14 trial. Between 2013 and 2015, 458 patients were randomized (BUMEL, n = 230; MEL200, n = 228). The 10⁻⁶ MRD-negative rate was 63%, 68% for BUMEL vs 58% for MEL200 (odds ratio, 1.51; P = .035). The median PFS was 89 months for BUMEL and 73.1 for MEL200 (hazard ratio, 0.89 [95% confidence interval, 0.70-1.14]; P = .3). BUMEL showed benefit for patients with ISS stages II or III, t(14;16), and del(1p). For subcohorts ISS stages II or III treated with BUMEL and ISS I treated with MEL200 the median PFS was 96.5 months (95% confidence interval, 76 to not estimable). No safety concerns were observed. After a median follow-up of 8.4 years, GEM2012 demonstrated one of the longest PFS values reported in patients with NDMM, with significant differences favoring BUMEL in advanced ISS stages. The trial was registered at www.ClinicalTrials.gov as #NCT01916252 and at European Union Drug Regulating Authorities Clinical Trials as EudraCT 2012-005683-10.