The VcR-CVAD Regimen Produces a High Complete Response Rate in Untreated Mantle Cell Lymphoma (MCL): First Analysis of E1405 – A Phase II Study of VcR-CVAD with Maintenance Rituximab for MCL.

One approach to improving outcomes in Mantle Cell Lymphoma (MCL) is to incorporate newer targeted agents into standard chemotherapy regimens. As the proteasome inhibitor bortezomib (Velcade‘) achieved a 33% response rate in relapsed MCL, we hypothesized that the incorporation of Velcade (Vc) into a modified R-hyperCVAD chemotherapy backbone would result in a high complete response rate (CR). The new regimen, VcR-CVAD, was tested for safety and efficacy in a phase II study within the Wisconsin Oncology Network (UW) and demonstrated a CR rate of 77% (Kahl, ASH 2008). To determine the safety and efficacy of this regimen in a cooperative group setting, we initiated E1405: a phase II study of VcR-CVAD with maintenance rituximab (MR) for untreated MCL.

Eligible patients had histologically confirmed, previously untreated MCL, PS 0-2, and adequate end organ function. The treatment plan included: Velcade 1.3 mg/m² days 1 and 4, rituximab 375 mg/m² IV day 1, cyclophosphamide 300 mg/m² IV over 3 hrs q 12 hrs X 6 doses days 1-3, doxorubicin 50 mg/m² continuous infusion over 48 hrs days 1-2, vincristine 1 mg IV day 3, dexamethasone 40 mg po days 1-4. Cycles were repeated every 21 days for 6 cycles and all patients received G-CSF support. Patients achieving SD, PR, or CR received MR administered as 4 weekly treatments every 6 months for 2 years (protocol therapy). Patients had an option to receive high dose chemotherapy and autologous stem cell transplantation (off protocol) rather than MR. The primary endpoint of the trial was the CR rate, incorporating PET imaging, to VcR-CVAD induction therapy.

Seventy-six eligible patients were enrolled between 5/07 and 10/08. Baseline characteristics include median age 62 (40-76), 59M:17F, 91% stage III/IV, and 39% with elevated LDH. Sixty-four patients (84%) completed VcR-CVAD induction therapy. Reasons for treatment discontinuation included PD (1), toxicity (4), patient preference (2), and other/unknown (5). Response information is available on 74 patients while data is outstanding on 2 patients. The ORR was 96% (73/76; 95% CI, 89%-99%), CR rate 75% (57/76; 95% CI, 64%-84%) and the PR rate 21% (16/76; 95% CI, 13%-32%). Six of the PR patients were coded as such because of protocol violations in which a post-treatment bone marrow biopsy or PET scan was not obtained. The CR rate in the 68 completely restaged patients was 84%. Forty-four patients proceeded to planned MR while 21 patients went off protocol to SCT consolidation. Median follow up is currently too short (9 months) to assess PFS and OS. The major toxicity of the treatment regimen was expected myelosuppression. Grade 3-4 non hematologic toxicities were rare. No patients developed grade 3-4 neuropathy. There were no treatment related deaths.

The VcR-CVAD induction produced high overall response (96%) and CR rate (75%) in a representative MCL patient population treated on a cooperative group protocol. The CR rate was high and comparable to the UW pilot study (77%). No episodes of severe painful peripheral neuropathy were reported using the reduced vincristine dosage and the overall toxicity profile was very acceptable. Longer follow up is needed to determine if the high CR rate will translate into improved PFS and OS.

Kahl:Genentech: Consultancy, Research Funding; Millennium: Consultancy, Research Funding. Off Label Use: Bortezomib as front line treatment in MCL. Smith:Genentech: Research Funding; Millennium: Research Funding. Advani:Seattle Genetics, Inc.: Research Funding. Horning:Genentech: Honoraria, Research Funding.