Abstract

Background

Bortezomib-based combinations, including alkylating agents (VMP or CyBorD) or immunomodulatory drugs (VTD or RVD) have been established as regimens widely used in newly diagnosed MM patients. Bendamustine is a bifunctional alkylating agent effective in relapsed and/or refractory MM patients, and approved in Europe in combination with prednisone for elderly newly diagnosed MM. Since bendamustine may be more efficient than other alkylators, an attractive possibility would be to explore it in combination with bortezomib and prednisone (BVP) in newly diagnosed MM patients both transplant and non transplant candidates.

Patients and Methods

60 newly diagnosed MM patients were included in the trial. The first cycle consisted on bendamustine at 90 mg/m2 given IV on days 1 and 4, in combination with bortezomib at 1,3 mg/m2 given IV on days 1, 4, 8, 11, 22, 25, 29 and 32 and prednisone at 60 mg/m2 given PO on days 1 to 4. In the following cycles, bendamustine was given on days 1 and 8, and bortezomib on days 1, 8, 15 and 22 (weekly schedule), and prednisone as it was previously described. Patients younger than 65 years proceeded to peripheral blood stem cell collection (PBSC) using growth factors alone after 4 cycles; HDT-ASCT was performed after 6 cycles. Patients older than 65 years received up to nine 28-day cycles.

Results

Between May 2011 and July 2012 enrollment was completed (60 pts). Median age was 61 years (range 38-82; 18 pts ≥65), 67% had ISS stage II/III, and 67% had unfavorable cytogenetics: t(4;14), t(14;16), del 17p or 1q gains by FISH.

After a median of 6 cycles (2-9), 75% of patients achieved at least PR, including 16% of sCR, 9% CR and 28% of VGPR. Although the differences were not statistically significant, there was a trend to higher CR rate in the group of patients <65 years (31%) compared with elderly patients (11%). No differences were observed in overall response rates and CR rates in patients with standard and high risk cytogenetic abnormalities.

Forty patients proceeded to stem cell collection after a median of 4 cycles of BVP. Upon using G-CSF alone, 14 pts (35%) failed to collect a minimun of 2 x 106 CD34+ cells/Kg. An ammendment was done and plerixafor was recomended for poor mobilizers (peripheral CD34 cell count inferior to 10/μL on day 4); all patients but 2 achieved, with G-CSF plus plerixafor, the minimum of CD34+ cells required to proceed to ASCT. These 2 patients successfully collected CD34+ cells using chemotherapy plus G-CSF and plerixafor. Of the 31 patients who received HDT-ASCT, sCR and CR rate before transplant was 18% and 13%, respectively, upgrading up to 39% of sCR and 13% CR after transplant. 7 pts (22%) achieved immunophenotypic CR.

After a median f/u of 12 months (5-25), 8 pts have progressed, resulting in a 15-m TTP of 85%. Concerning OS, 89% of patients remained alive at 15 months. None of patients achieving sCR and CR have progressed and all of them are alive at 15 months. Regarding cytogenetic abnormalities, although there were not significant differences, one patient progressed in standard risk group and five in the high risk subgroup resulting in a 15 m-TTP of 93% vs 85%. No significant differences have been observed in terms of 15 m-OS between standard and high risk cytogenetic subgroup (100% vs 92%, respectively).

As far as toxicity is concerned, hematologic toxicities included: G3/4 anemia (11%), neutropenia (23%), and thrombocytopenia (14%). The most common G3/4 non-hematologic toxicities were: asthenia (10%), infections (9%), and peripheral neuropathy (4%).

Conclusions

In patients candidates to HDT-ASCT, response rates obtained before and after transplant are comparable to other three drug bortezomib-based combinations, such as VTD or CyBorD. However, growth factors alone for stem cell collection after four BVP cycles as induction resulted in a 35% of poor mobilizers who were rescued with plerixafor. In the elderly population, although the number of patients included was small, BVP seems not superior to VMP in response rates.

Disclosures:

Mateos:Janssen, Mundipharma: Honoraria. Off Label Use: bendamustine plus bortezomib and prednisone is not an approved combination for first line of therapy. Oriol:Celgene: Consultancy. Ocio:Onyx: Consultancy, Research Funding; Novartis: Consultancy; Array Biopharma: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy; Celgene: Consultancy, Research Funding. Alegre:Celgene: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity’s Board of Directors or advisory committees, Research Funding. Bladé:Janssen, Mundipharma: Honoraria. San Miguel:Janssen, Mundipharma: Membership on an entity’s Board of Directors or advisory committees.

Author notes

*

Asterisk with author names denotes non-ASH members.