Bortezomib, Thalidomide, and Dexamethasone (VTD) Versus VTD Plus Cyclophosphamide as Induction Therapy in Previously Untreated Multiple Myeloma Patients Eligible for HDT-ASCT: A Randomized Phase 2 Trial.

Abstract 2312

Poster Board II-289

Bortezomib (Velcade^®) has shown substantial activity and manageable toxicity in newly diagnosed multiple myeloma (MM) in combination with thalidomide (Thalomid^®) and dexamethasone (VTD) in a phase 3 study (Cavo et al, ASH 2008), and with cyclophosphamide and dexamethasone (VCD) in a phase 2 study (Knop et al, ASCO 2009). Four-drug combinations may be more effective than 3-drug regimens, but may also be associated with increased toxicity. This randomized, non-comparative, open-label, multicenter, phase 2 study was designed to evaluate the efficacy and safety of VTD and VTD plus cyclophosphamide (VTDC) as induction therapy prior to high-dose therapy plus autologous stem cell transplant (HDT-ASCT). A total of 98 previously untreated MM patients with measurable disease who were candidates for HDT-ASCT were enrolled. Additional eligibility criteria included: age 18–70 years, Karnofsky Performance Status (KPS) ≥60%, adequate hematologic, hepatic, and renal function, and no grade ≥2 peripheral neuropathy (PN)/neuropathic pain. Patients were randomized (1:1), stratified by International Staging System (ISS) disease stage (I / II / III), to receive four 21-day cycles of bortezomib 1.3 mg/m² on days 1, 4, 8, and 11, thalidomide 100 mg daily, and dexamethasone 40 mg on days 1–4 and 9–12 (VTD), or VTD plus cyclophosphamide 400 mg/m² IV on days 1 and 8, as induction therapy prior to HDT-ASCT. All patients received antithrombotic prophylaxis. Patients who became ineligible for HDT-ASCT or had a complete response (CR) after induction therapy could receive an additional 4 cycles of treatment. Responses were categorized using modified IMWG Uniform Response Criteria (stringent CR [sCR] were unconfirmed by immunohistochemistry) through blinded review by the principal investigator and medical monitor, using central laboratory M-protein data and local bone marrow data. The primary efficacy endpoint was combined CR rate (sCR + CR + near-CR) following induction therapy. Secondary objectives included combined CR rate post-HDT-ASCT, overall response rate (ORR: ≥partial response) post-induction and post-HDT-ASCT, time to progression (TTP), overall survival (OS), and safety. Adverse events (AEs) were graded using NCI CTCAE v3.0. Forty nine patients were randomized to each arm; median age was 57 and 58 years in the VTD and VTDC arms, respectively, 53% and 51% of patients were male, 49% and 43% had KPS ≤80%, and 24 / 45 / 31% and 18 / 47 / 35% had ISS stage I / II / III MM. All but 7 patients completed induction; these patients discontinued due to AEs (3 [6%] each arm) and disease progression (1 [2%] VTDC). Four VTDC patients received additional cycles of treatment. One patient (VTDC arm) was not evaluable for response. Response rates following induction are shown in the table. Median CD34+ stem cell yields were 8.16 (VTD; n=48) and 8.13 (VTDC; n=40) x 10⁶/kg. At data cut-off (April 10, 2009), 47 VTD and 35 VTDC patients had undergone HDT-ASCT; response rates post-HDT-ASCT in 38 and 27 evaluable patients are shown in the table. Time-to-event data are not mature (median follow-up: 9.8 months). The 1-year survival rate was estimated to be 94% in each arm. At least one AE was reported in 98% and 96% of patients on the VTD and VTDC arms, with at least one grade ≥3 AE reported in 47% and 59%, respectively. The most common non-hematologic grade 3/4 AEs included fatigue (2% and 8%) and constipation (6% and 2%); analyses of hematology laboratory values indicated grade 3/4 AEs of lymphopenia (39% and 77%), anemia (8% and 18%), neutropenia (14% and 18%), and thrombocytopenia (6% each). PN was reported in 35% (VTD) and 29% (VTDC) of patients, including 8% grade 3 in each arm and 2% grade 4 in the VTD arm. Two patients (1 [2%] each arm) had deep vein thrombosis; one (VTDC arm) was a grade 3 SAE. At least one serious AE (SAE) was reported in 22% (VTD) and 41% (VTDC) of patients, including 6% and 14% with SAEs of infections (MedDRA SOC), and 2% and 14% with musculoskeletal-related pain. In conclusion, both VTD and VTDC are highly active induction regimens, with CR rates and ORRs among the highest reported; the efficacy profiles were similar between the arms, but there were higher rates of toxicity in the VTDC arm compared with the VTD arm.