Bortezomib with HIG-Dose Dexamethasone as First Line Therapy in Patients with Multiple Myeloma Candidates to High-Dose Therapy.

Introduction: A phase II multi-center study was performed to investigate the efficacy of Bortezomib with high-dose dexamethasone (Vel-Dex) as induction therapy in multiple myeloma (MM) patients (pts) candidates to high-dose therapy.

Methods: Patients were planned to receive 4 courses of Vel-Dex (Bortezomib 1.3 mg/m² i.v. on days 1, 4, 8, 11; oral Dexamethasone 40 mg on days 1–4 and 8–11 every 3 weeks), followed by 2 courses of DCEP 4 weeks apart with stem cell collection, and a single autologous transplant with melphalan 200 mg/m². Patients were untreated, aged ≤65 years, with Durie-Salmon stage III, II, or I in progression. Criteria of response were: CR: negative serum/urine immunofixation with <5% bone marrow plasmacytosis (BMPC); nCR: positive serum/urine immunofixation with <5% BMPC; VGPR/PR: reduction of at least 90%/50% of serum/urine monoclonal component (MC), and of BMPC. Adverse events (AE) were graded by the NCI-CTC version 3.0. Mann-Whitney U test was used to correlate response and main prognostic parameters.

Results: From March 2006 to June 2007, 52 out of the 54 planned pts entered the protocol. Patient characteristics at enrolment were: male/female 33/19; median age 57 years (37–65); IgG/IgA/light-chain 33/9/10 pts; stage III/II/I in progression 44/5/3 pts; ISS I/II/III 21/14/17 pts; cytogenetic analysis showed del 13 in 54%, t (4;14) in 15%. Thirty-nine of 52 enrolled pts are evaluable for efficacy and toxicity after 4 Vel-Dex courses. Six pts were withdrawn (3 for progression, 2 for toxicity, 1 patient withdrew informed consent). Overall response rate (ORR) was 85%, with 67% major responses (CR 33%, nCR 26%, VGPR 8%), PR 18%, stable disease 7%, progression 8%. No statistically significant correlation was found between response and either age, stage, ISS, or unfavorable cytogenetics. Friedman ANOVA (p=0.00001) and Wilcoxon Matched Pairs (p<.05) tests showed a statistically significant progressive decrease of serum MC after each Vel-Dex cycle. Urine MC and serum free light chain ratio showed a strikingly rapid reduction after the first course with no further statistically significant decrease during the following courses. Regarding toxicity, NCI grade 1 or 2 AE were: infection (19), constipation (16), peripheral neuropathy (13), diarrhea (9), gastritis (6), nausea (5). NCI grade 3 AE were: infection (9) with 5 varicella-zoster, peripheral neuropathy (4), cardiac arrhythmia (2). A single grade 4 AE (fatal sepsis) occurred. At the time of this analysis, 25 pts completed the stem cell mobilization phase. All pts collected adequate number of stem cells (median CD34+ cells 6.2x10⁶/kg, range 3.5–18.0x10⁶/kg, median number of collection procedures 1).

Discussion: This study shows that Vel-Dex as first line therapy produces high response rates in MM pts (ORR 85%, major response 67%). Toxicity was generally predictable and manageable. Stem cells were successful harvested in all patients. Vel-Dex appears an effective and safe pre-transplant treatment for younger MM patients.