Thalidomide / Dexamethasone (TD) Vs. Bortezomib (Velcade)^â/Thalidomide / Dexamethasone (VTD) Vs. VBMCP/VBAD/Velcadeâ as Induction Regimens Prior Autologous Stem Cell Transplantation (ASCT) in Multiple Myeloma (MM): Results of a Phase III PETHEMA/GEM Trial.

Abstract 130

In April 2006, the Spanish Myeloma Group (PETHEMA/GEM) activated a randomized phase III trial comparing TD vs. VTD vs. VBMCP/VBAD/Velcade^â in patients 65 years-old or younger with newly diagnosed symptomatic MM, followed by ASCT with MEL-200. The primary end points were response rate after induction and after ASCT and time to progression. TD consisted of thalidomide 200 mg daily (escalating doses in the first cycle) and dexamethasone 40 mg on days 1–4 and 9–12 at 4-week intervals for 6 cycles. The VTD regimen was identical to TD plus Velcade 1.3 mg/m² on days 1,4,8,11 of each cycle. Combination chemotherapy plus Velcade^â consisted of 4 cycles of VBMCP/VBAD on an alternating basis followed by 2 cycles of Velcade^â (1.3 mg/m² on days 1,4,8, and 11 every 3 weeks). The duration of the induction therapy was 24 weeks in all arms. From April 6, 2006 to August 5, 2009 the 390 planned patients entered the study. As of December 31, 2008, 305 patients (median age: 57 yrs, M: 156, F:149; IgG. 181, IgA: 71, light chain: 43, others: 10) entered the study and are the basis of the current analysis. Fifty-six (18%) patients had soft-tissue extramedullary plasmacytomas (EMP) and the stage according to the ISS was I in 39%, II in 41 %, III in 19 % and unknown in 1%. The prognostic factors, including cytogenetics, was similar in the 3 arms. Fifty-five (18%) patients had high-risk cytogenetics (t(4;14), t(14;16) and/or 17p deletion). Two-hundred and ninety-nine patients (TD:103, VTD: 99 and VBMCP/VBAD/Velcade^®: 97) were evaluable for response and toxicity to induction therapy. The ≥ PR rate was 64%, 82% and 75% with TD, VTD and VBMCP/VBAD/Velcade^®, respectively (p=NS). The IF negative CR rate was significantly higher with VTD (29%) and with VBMCP/VBAD/Velcade^® (25%) than with TD (14%) (p=0.009 and p=0.04, respectively). Progressive disease (PD) was significantly higher with TD than with VTD (21% vs. 8%, p=0.009). In the overall series, PD was significanty higher in patients with EMP (34% vs. 12%, p=0.0002) with a significanty higher PD rate for TD as compared with VTD (40% vs. 14%, p=0.05). In patients with poor cytogenetics the CR rate was significantly higher with VTD than with TD (42% vs. 5%, p=0.009). In this high-risk group the PD rate was higher with TD (37%) and with VBMCP/VBAD/Velcade^® (23%) than with VTD (0%) (p=0.009 and p=0.04, respectively). The incidence of thrombotic events ≥ grade 3 was higher in the TD arm (9% vs. 1% vs. 3%, p=0.07 and p=0.01) while ≥3 peripheral neuropathy was higher with VTD (14% vs. 0% and 1%, p<0.0001 and p=0.0003). Treatment was discontinued due to toxicity in 11 patients (TD: 3, VTD: 6, VBMCP/VBAD/Velcade^®:2). Eight patients died during induction period (TD:5, VTD: 2, VBMCP/VBAD/Velcade^®: 1) One-hundred seventy-seven patients were evaluable for response after ASCT. The post-ASCT CR rate with TD, VTD and VBMCP/VBAD/Velcade^® was 40%, 59% and 48%, respectively, being significantly higher with VTD than with TD (p=0.05). The estimated overall survival at 2 years is 82% with no significant differences among the 3 arms. TTP and PFS were significantly shorter with TD (p=0.05 and p=0.012, respectively). In summary, VTD results in a higher pre- and post-ASCT CR rate as well as in a lower PD rate than TD, particularly in patients with high-risk cytogenetics or with EMP. The TTP and PFS are shorter with TD. Intermediate results are observed with VBMCP/VBAD/Velcade^®. Longer follow-up is needed to establish whether or not these results will translate into a significantly different long-term outcome. Updated data will be presented at the meeting.