A Phase II Trial of Myeloma Induction Therapy with Cyclophosphamide, Bortezomib, and Dexamethasone (Cybor-D): Improved Response over Historical Lenalidomide-Dexamethasone Controls.

Background: We previously reported an 85% response rate with 54% CR/nCR using a combination of cyclophosphamide (Cy), prednisone, and bortezomib (BZ) in relapsed myeloma (MM). We now report a Phase II clinical trial using a combination of Cy, BZ, and dexamethasone (Dex) [Cybor-D] in newly-diagnosed MM. We then compare the activity of this combination with historical controls treated with our current induction standard of Lenalidomide-Dexamethasone (L-Dex).

Methods: 30 patients have been enrolled on Cybor-D. Treatment consists of Cy 300mg/m² p.o. days 1, 8, 15, and 22; BZ 1.3 mg/m² days 1, 4, 8, and 11, and Dex 40mg p.o. days 1–4, 9–12, 17–20. Prophylactic use of acyclovir, a quinolone and antifungal prophylaxis was highly recommended for all patients on study. Growth factors were allowed. As a relevant contemporaneous control for speed and depth of response, we used 33 patients treated on a recent Mayo Clinic trial of L-Dex (Rajkumar. Blood: 2005 106;4050–3). Response was defined according to IMWG criteria although in the current trial, bone marrows for confirmation of CR are not yet available on all patients.

Results: At time of current analysis, 17 patients on Cybor-D were evaluable through at least one cycle for response and toxicity. Baseline characteristics included mean age of 57, 29% female, 41/24% ISS stage II/III. There were statistically more early stage patients on L-Dex; otherwise, baseline patient characteristics were similar. The mean % decline in monoclonal (M) protein from baseline following cycles 1–4 of Cybor-D were 71%, 90%, 93%, 96%. This compares favorably with L-Dex where equivalent % decline in M proteins were 66%, 77%, 80%, and 79%. Thus, in preliminary results, Cybor-D produces a more rapid initial decline and mean % reduction in M protein than L-Dex. Overall response rate (≥ PR) after one cycle of Cybor-D was 77% with 36% obtaining ≥VGPR (L-Dex 73% and 18% respectively). The % of patients obtaining ≥VGPR after each cycle was 36%, 64%, 77%, and 100% for Cybor-D as compared to 18%, 36%, 42%, and 33% for L-Dex. The overall ≥VGPR at the end of four cycles of Cybor-D is currently100% (≥ 66%nCR using older nomeclature). Major toxicities ≥ grade 3 for Cybor-D included hematologic (37%), hyperglycemia (15%) and neuropathy (11%).

Conclusions: In summary, for newly-diagnosed MM patients, four cycles of Cybor-D produces more frequent, rapid and deep responses when contrasted with historical L-Dex controls. Further confirmation of response rates and effect on TTP will be required.