Bendamustine, Bortezomib and Dexamethasone (BVD) in Patients with Relapsed-Refractory Multiple Myeloma (MM): Updated Results of a Multicenter Phase II Study

Introduction: Bendamustine, a bifunctional alkylating agent, exerts a mechanism of action different from that of other conventional alkylators despite it remains mostly unknown. In patients with newly diagnosed or relapsed-refractory MM bendamustine has proven to be active either as monotherapy or in combination with new drugs, particularly bortezomib and immunomodulatory agents.

Methods: The preliminary results of this prospective, phase II study conducted in 22 Italian centres are recently published (Blood Cancer J. 2013, 3: e162). Here we present the conclusive results of the combination Bendamustine (70 mg/m² days 1, 8), Bortezomib (1.3 mg/ m² days 1, 4, 8, 11) and Dexamethasone (20 mg days 1-2, 4-5, 8-9, 11-12) (BVD) administered every 4 weeks in patients with relapsed-refractory MM of any age, with adequate cardiac, liver and hematological function, not refractory to bortezomib and treated with no more than four previous lines of therapy. The primary endpoint of this study was achievement of a response at least PR, as to IMWG criteria, after four cycles of BVD. Patients achieving a response less than a PR were taken off-study. Patients obtaining at least a PR received two additional treatment cycles followed by a 12-months consolidation phase with cycles repeated every 2 months. Therefore, patients with a PR after the induction phase could receive up to 18 months of treatment and up to 12 cycles of BVD.

Results: 75 patients were included in the study. Median age was 68 years (range 41-85 years), 26.5% had ISS stage 3, 19% IgA myeloma and 9% renal failure. Eight of 36 evaluable patients (22%) had high-risk cytogenetics. Patients had received a median of one prior line of therapy (range 1-4). All patients had received prior treatment with new drugs, such as thalidomide (57%), lenalidomide (54.5%), bortezomib (46.5%) or both (20%). Twenty-four patients (32%) were refractory to IMIDs.

Best response rate was 75%, including 14 CRs (20%), 22 VGPRs (24%) and 27 PRs (31%). Five patients (6.5%) died early. Only prior treatment with bortezomib significantly reduced the response rate ≥ PR (48.5% vs 80%; P = 0.004). At a median follow-up of 27 months (range 18-38), 45 patients had progressed and 43 had died. Median TTP and PFS were 17 and 12.5 months, respectively while median OS was 24 months (40% at 3 years). After longer follow-up, prior therapy with bortezomib plus lenalidomide was confirmed as the only factor that significantly reduced TTP (9 vs 19 months; HR = 2.7; 95% CI = 1.3-5.8; P = 0.009), PFS (9 vs 15 months; HR = 2.1; 95% CI = 1.2-3.8; P = 0.020) and OS (17 vs 32 months; HR = 2.1; 95% CI = 1.2-3.9; P = 0.043).

Grade 3-4 adverse events occurred in 55% of patients leading to therapy reduction in 24% and to protocol discontinuation in 11% of patients. The most frequent severe adverse events were thrombocytopenia (28%), neutropenia (20%), infections (12%), peripheral neuropathy (9%), gastrointestinal (5%) and cardiovascular events (4%). Compared with younger, patients aged > 70 years had a significantly higher incidence of grade 3-4 side effects particularly thrombocytopenia and infections with, consequently, a higher rate of therapy reduction and discontinuation. Moreover, 4/5 early deaths occurred in patients aged more than 70 years.

Conclusions: BVD combination is an effective and well tolerated regimen in relapsed-refractory MM. Data suggest that the optimal target of BVD maybe patients younger than 70 years who has not previously received both bortezomib and lenalidomide.