A Prospective, Multicenter, Randomized, Trial of Bortezomib/Melphalan/Prednisone (VMP) Versus Bortezomib/Thalidomide/Prednisone (VTP) as Induction Therapy Followed by Maintenance Treatment with Bortezomib/Thalidomide (VT) Versus Bortezomib/Prednisone (VP) in Elderly Untreated Patients with Multiple Myeloma Older Than 65 Years.

Abstract 3

In elderly pts with newly diagnosed MM, the VISTA trial has demonstrated that the combination of bortezomib plus melphalan – prednisone (VMP) is significantly superior to MP alone. However, it remains to be elucidated which agent is the optimal partner for bortezomib: an alkylating agent or an immunomodulatory drug. In order to answer this question, Spanish Myeloma Group activated a phase III trial comparing VMP versus VTP (T for thalidomide) as induction therapy. To evaluate if the treatment regimen could be further optimized by decreasing the toxicity while maintaining efficacy, the intensity of both schedules of induction was reduced as compared with the VISTA regimen but supplemented with maintenance therapy. Between April 2005 and October 2008, 260 pts were randomized to receive 6 cycles of VMP vs VTP as induction therapy followed by maintenance with VT vs VP for up to three yrs. In the VMP arm pts received bortezomib 1.3 mg/m² twice weekly (days 1, 4, 8, 11; 22, 25, 29 and 32) for one 6-week cycle, followed by once weekly (days 1, 8, 15 and 22) for five 5-week cycles in combination with oral melphalan 9 mg/m² and prednisone 60 mg/m² once daily on days 1–4 of each cycle. In the VTP arm pts received the same bortezomib and prednisone, but instead of melphalan they received thalidomide at a dose of 100 mg daily. Following the 6 cycles of induction, pts moved into maintenance that consisted in a conventional cycle of bortezomib, 1.3 mg/m² twice weekly (days 1, 4, 8, 11) administered every three months in combination with either continuous thalidomide, 50 mg daily (VT) or prednisone, 50 mg on alternate days (VP).

253 pts are evaluable for response to induction; 125 were assigned to receive VMP and 128 to VTP. Regarding baseline characteristics, both arms were well balanced. Response rate to induction therapy was similar in both arms: ≥ PR in 81 and 79% of pts treated with VMP and VTP respectively, with a CR rate of 22% vs 27% (p=NS) and CR+nCR of 36% in both arms. Only two pts progressed under induction treatment in each arm. After a median follow-up of 22m (8-40), there weren't significant differences in terms of 2-y TTP (VMP 75% vs VTP 70%), PFS (VMP 71% vs VTP 61%) and OS (VMP 81% vs VTP 84%). 178 pts were randomized to maintenance and 143 are evaluable for efficacy. Overall, maintenance therapy was able to increase the CR rate from 25% (mean obtained after induction therapy) up to 42%, with no significant differences between VT and VP arms (46 and 38%). After a median duration of maintenance of 13 m there is a trend in favour of VT in terms of 1-y TTP (84% vs 71%; p=0.05), without differences in 1-y OS (92% for VT vs 89% for VP).

27 pts presented high-risk cytogenetic abnormalities (CA) ((4;14)t, (14;16)t, del[17p]); the CR rate was similar in this high-risk group as compared with standard risk group (26% vs 25% after induction and 42% after maintenance in both groups). There aren't differences between high-risk and standard-risk pts in the 2-y TTP (74% vs 73%) and 2-y OS (77% vs 81%) from inclusion; however, there is a trend to lower 1 y-TTP from the time to randomization to maintenance for the high-risk group compared to the standard-risk (68% vs 79%) without differences in 1 y-OS (90% vs 93%).

Regarding toxicity, during the induction therapy, VMP resulted in higher incidence of ≥G3 neutropenia than VTP (37 vs 21%) and this translated into more ≥G3 infections (7 vs <1%); 8,5% of pts receiving VTP developed ≥G3 cardiac events (cardiac failure (5), atrial fibrillation (2), hypotension (2), heart attack (1) and AV blockage (1)). The incidence of ≥G3 PN was 5% in VMP and 9% in VTP (p=NS). During maintenance therapy, the most relevant ≥G3 toxicities included: cardiac events in 2 pts in VT (supraventricular arritmia (1) and heart attack (1)) vs 1 in VP (cardiac failure); G-I events in 4 pts in VT vs 1 in VP; finally, only one patient in VT arm died during the maintenance therapy due to sepsis. In summary the current results indicate that: 1. both modified induction schedules (VMP and VTP) are highly effective with similar ORR and CR rates, but a clear different toxicity profile (more neutropenia, but less cardiac toxiciety and PN with VMP); 2. maintenance therapy with either VT and VP markedly improve the quality of responses with a good safety profile; and finally 3. the combination of these induction and maintenance schedules seems to overcome the poor prognosis of high-risk CA in elderly MM patients.