Analysis of VDT-PACE Utilization in Multiple Myeloma Patients Treated at MSKCC for Relapsed Disease or Cytoreduction and Stem Cell Mobilization after Initial Induction Therapy

Background: The total therapy 3 protocol for multiple myeloma (MM) introduced the use of intensive induction with VDT-PACE, a combination of bortezomib, dexamethasone, thalidomide, cisplatin, adriamycin, cyclophosphamide, and etoposide for newly diagnosed MM patients. This regimen, which demonstrated rapid responses in the first-line setting, has also been used in relapsed disease, to rescue induction failures or for stem cell mobilization. We evaluated the efficacy and toxicity of using VDT-PACE in these clinical settings.

Patients and Methods: We identified 84 patients through pharmacy profile review who received at least one cycle of VDT-PACE for the treatment of MM between 1/2007 and 8/2013 at our institution. Patients were grouped into a stem cell collection cohort (C) if stem cell pheresis was performed following VDT-PACE. Remaining patients were analyzed in the relapsed cohort (RR). The primary objective of this study was to determine the overall response rate with combination VDT-PACE. Secondary Objectives include progression-free survival (PFS), overall survival (OS), stem cell collection in patients that underwent chemomobilization, and the extent of toxicity.

Results: In the RR group, 45 patients received VDT-PACE after a median of 4 prior therapies (range 1-8) including autologous stem cell transplantation (ASCT) in 79%. The median time between diagnosis and first cycle of VDT-PACE treatment was 35.4 months (range 1.3-163.4). 47% of patients had adverse cytogenetics defined as presence of complex karyotype or FISH with del 17p, t4;14, or t14;16. Patients received a median of 2 cycles of VDT-PACE (range 1-4) with a response rate after all cycles of 51% (2% CR, 22% VGPR, 27% PR). Additional therapy was administered in 82% within 6 months (18% allogeneic SCT, 35% ASCT, 29% chemotherapy regimens). 18% of patients died without additional therapy (13% from disease progression, 5% from toxicity), all within 5 months of their last VDT-PACE cycle. PFS and OS for the RR group was 8.8 months (95% CI 4.6, 13.1) and 10.3 months (95% CI 8.8, 17.4), respectively. Patients that received subsequent lines of therapy following VDT-PACE achieved a median PFS and OS of 9.5 months (95% CI 5.6, 13.3) and 9.5 months (95% CI 7.5, 32.1), respectively, measured from the time of next therapy.

In the C group, 39 patients received a median of 2 prior regimens (range 1-4) before starting VDT-PACE and 31% of patients had adverse cytogenetics. Reasons for using VDT-PACE for mobilization included residual or progressive disease (64%), provider discretion (33%), and failure of a prior attempt at collection (3%). The median time between diagnosis and first cycle of VDT-PACE treatment was 7 months (range 2.3-122.7). Patients received a median of 2 cycles (range 1-4) of VDT-PACE. The median number of cells collected was 12.3x10⁶CD34 cells/kg (range 0.21-43.74) and the median number of collection session required was 2 (range 1-6), with 21% of patients requiring plexirafor. Two patients (5%) from this group failed collection. The response rate after all cycles of VDT-PACE was 59% (3% CR, 13% VGPR, 44% PR). 35 out of the 39 patients went to transplant following VDT-PACE (34 ASCT, 1 allogeneic SCT). Of the 4 patients who did not receive transplant, 2 were for toxicity attributed to VDT-PACE, 1 for failure to mobilize, and 1 for personal reasons. The post-transplant response rate was 91% (17% CR, 34% VGPR, 40% PR) with 1 patient (3%) experiencing disease progression immediately after transplant. Median PFS and OS for the C group patients was 34.5 months (95% CI 20.2, n.r.) and 64.8 months (95% CI 26.0, n.r.), respectively.

Reported toxicities following treatment included infection (20%), fatigue (19%), nausea (17%), renal complications (6%), thrombosis (4%), and edema (4%), which were seen in 67% and 62% of the RR and C groups, respectively. Hospital readmission for management of side effects occurred in 30% of patients.

Conclusions: VDT-PACE is an effective therapy for RR patients and for stem cell mobilization in patients with residual or progressive disease following initial therapy. Importantly, it is also associated with significant morbidity and requires careful monitoring. VDT-PACE does not appear to adversely affect stem cell collection or SCT outcomes. At our institution, this regimen is commonly used for stem cell collection in patients with unfavorable outcomes following initial therapy.