Bendamustine, Bortezomib and Dexamethasone (BVD): A Combination With a Substantial Activity and a Manageable Toxicity In Patients With Relapsed-Refractory Multiple Myeloma (MM)

Bendamustine, a bi-functional alkylating agent comprising a purine-like benzimidazole ring an a nitrogen mustard group, exerts a peculiar mechanism of action if compared to most conventional alkylators and this may partially explain its effectiveness in alkylator-resistant cells. In patients with MM several studies demonstrated the efficacy and tolerability of bendamustine as monotherapy or in combination with new drugs, particularly bortezomib that was found to enhance the in vitro sensitivity of MM cells to bendamustine.

These observations represented the rationale for our protocol design namely to evaluate 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). Cycles were administered every 4 weeks up to four cycles. 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. 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 were enrolled in this prospective, single-arm, open-label, phase II study conducted in 21 Italian centres. The primary endpoint was achievement of a response at least PR after four cycles of BVD and response was assessed according to to IMWG criteria.

From March 2011 to June 2012, 75 patients were included. Median age was 68 years (range 41-85), 26.5% had ISS stage 3, 19% IgA myeloma and 9% renal failure. In total, 8 of 36 evaluable patients (22%) had adverse cytogenetics. All patients had received prior treatment with new drugs, including targeted agents such as thalidomide (57%), lenalidomide (54.5%) or bortezomib (46.5%). Patients had received a median of one prior line of therapy (range 1-4), including alkylators (69%), anthracyclines (29%) and ASCT (44%). Twenty-four patients (32%) were refractory to IMIDs.

The response rate ≥ PR after four cycles of BVD was 71.5%, including 11 patients with CR (16%), 13 VGPRs (18.5%) and 26 PRs (37%). Also, 14 patients (20%) had disease stabilization while 6 (8.5%) had progressive disease. Median time to response was 1.2 months (range 0.9-1.4 months). Only prior treatment with bortezomib significantly reduced the response rate ≥ PR (54.5% vs 86.5%; P = 0.003).

At a median follow-up of 12 months (range 6-24), 30 patients had progressed and 18 had died. Median TTP and PFS were 16.5 months and 15.5 months, respectively while median OS had not been reached and 78% of patients were alive at 1 year. The Cox regression analysis identified prior therapy with bortezomib plus lenalidomide as the only factor that significantly reduced TTP (9 vs 17 months; HR = 4.5; 95% CI = 1.7-12.3; P = 0.005)

Grade 3-4 adverse events occurred in 55% of patients leading to therapy reduction in 20% and to protocol discontinuation in 10.5% of patients. The most frequent severe adverse events were thrombocytopenia (30.5%), neutropenia (18.5%), infections (12%), peripheral neuropathy (8%), gastrointestinal and cardiovascular events (both 6.5%). Compared with younger, patients aged > 70 years had a significantly higher incidence of grade 3-4 thrombocytopenia (22% vs 37%; p=0.042) and severe infections (7 vs 19%; p=0.047) and consequently a higher rate of therapy reduction (9% vs 34.5%; p=0.007) and therapy discontinuation (7% vs 15.5%; p=0.043). Moreover, 4/5 early deaths occurred in patients aged more than 70 years.

BVD combination is an effective regimen in relapsed-refractory MM patients since it elicits rapid, high (> 70%) and good quality of response (more than a third of patients achieved CR + VGPR). Moreover, BVD combination is a feasible and well tolerated regimen provided that adapted therapy and adequate antibiotic prophylaxis are employed in patients older than 70 years.