Bortezomib-Based Therapy, without Stem Cell Transplantation, for Newly Diagnosed Multiple Myeloma Patients with t(4;14).

Abstract 3861

Poster Board III-797

Previous studies have reported that multiple myeloma (MM) patients (pts) with t(4;14) identified by FISH who are treated with a single ASCT as part of first-line therapy have worse outcomes than those lacking this adverse cytogenetic marker; two trials have described a median progression-free survival (PFS) of only 8-9 months and median overall survival (OS) of 18 mos in this setting (Chang H, et al. Bone Marrow Transplant 2005; 36: 793; Gertz M, et al. Blood 2005; 106: 2837). Since the novel agent bortezomib appears to have efficacy in patients with t(4;14), we designed a phase II protocol in which pts receive induction with pegylated liposomal doxorubicin, bortezomib and dexamethasone (DBD) x 4 cycles, followed by post-induction therapy with oral cyclophosphamide 300 mg/m² days 1,8 15, 22 with bortezomib 1.5 mg/m² days 1,8,15 and prednisone 100 mg q 2 days of a 28-day cycle (CyBor-P) x 8 additional cycles. Maintenance therapy with dexamethasone (dex) 40 mg/month was then administered until progression. Although elective stem cell collection was recommended after induction, routine ASCT was not performed in the absence of disease progression. Between February 2008-August 2009, 153 newly diagnosed MM pts were screened for t(4;14) in 7 Canadian centers, and 14 (9%) were found to be positive by FISH. Four did not meet the critieria for symptomatic MM, 2 had received ≥ 2 mos of prior therapy while 8 were entered onto study. One of these was later determined to have a variant abnormality of chromosome 4 but not t(4;14) and underwent ASCT after induction; this pt is included in the safety analysis only. The median age was 56 (49-69) and 43% were male. The median percent nuclei positive for t(4;14) was 30% (10-41%), serum β2-microglobulin 394 nmol/L (190-1695) and albumin 34 g/L (28-39); one pt had ISS stage 1,3 had stage 2 and 3 had stage 3 MM. Immunoglobulin subtype included IgGκ in 2 and IgAκ in 2 and IgAλ in 3. All pts have completed DBD induction, with the best response in the 7 evaluable pts consisting of PR in 2 and VGPR in 5; one in PR progressed quickly after induction and has achieved nCR after D-PACE followed by ASCT and lenalidomide maintenance. Four are receiving post-induction therapy with CyBor-P currently, with VGPR in 3 and PR in 1. No SAEs or grade3/4 neutropenia or thrombocytopenia has occurred; other toxicities were mild, with grade 2 skin toxicity noted in 37.5% and grade 2 neurotoxicity observed in 7.4%. All pts are alive at a median follow-up (F/U) of 8 mos (2-11), and 6 (86%) are free of progression. We conclude: 1) the incidence of t(4;14) in newly diagnosed MM pts appears to be lower than the 15% anticipated; 2) 28% of newly diagnosed pts with this entity have asymptomatic MM; 3) preliminarily, DBD induction has resulted in ≥ PR in all pts although 1 progressed quickly; 4) this bortezomib-based regimen is very well-tolerated; 5) longer F/U is required to determine the PFS and OS with this approach.