A Phase I/II National, Multi-Center, Open-Label Study of Bortezomib Plus Melphalan and Prednisone (V-MP) in Elderly Untreated Multiple Myeloma (MM) Patients.

Background: Although clearly unsatisfactory, melphalan and prednisone remains the gold standard for elderly MM patients. Therefore new treatment strategies are needed for these patients. The proteasome inhibitor bortezomib (VELCADE) has shown significant activity in refractory/relapsed MM patients. Moreover, in vitro synergy has been reported when bortezomib is combined with cytotoxic agents such as melphalan.

Aim: To define the appropriate dose of bortezomib in combination with MP and to analyse the toxicity and efficacy of V-MP (in terms of response) in untreated MM pts ≥ 65 years old.

Methods: Treatment schedule consisting of four 6-week cycles followed by five 5-week cycles. First, two sequential dose levels of bortezomib (1.0 and 1.3 mg/m²) (6 pts each) were explored, administered on days 1,4,8,11,22,25,29 and 32 in combination with oral melphalan, 9 mg/m² and prednisone, 60mg/m² once daily on days 1 to 4. When maximum tolerated dose (MTD) of bortezomib in combination with MP was defined, the cohort of pts at the MTD was expanded to up to 60 patients to further refine estimates of efficacy and toxicity (PhaseII).

Results: Median age of the 60 enrolled pts was 74(65–85) and the median number of cycles so far received is 3(1–9). During PhaseI, no dose limiting toxicity(DLT) was observed in the two cohorts of pts, and the recommended dose for phaseII was 1.3 mg/m² of bortezomib in combination with MP. 53pts are evaluable for efficacy since they have already completed at least the first cycle. Analysis of response after cycle 1 revealed a Response Rate(RR) of 72%(6%CR with Immunofixation negative(CRIF-), 2%CRIF+ and 64%Partial Response(PR)). Analysis of best response after a median of 3 cycles revealed a RR of 85%(28%CRIF-, 11%CRIF+ and 45%PR); an additional pt(2%) achieved Minor Response(MR) and 7(13%) stable disease. The toxicity was manageable. Adverse events G3-4 reported for 60 pts included: Gastrointestinal toxicity, such as nauseas(2%), vomiting(2%), diarrhoea(15%) and constipation(8%); haematological toxicity, such as anemia(12%), neutropenia(G3 in 26% and G4 in 13%) and thrombocytopenia(G3 in 33% and G4 in 13%); infection(G3 en 12% and G4 in 2%) and peripheral neuropathy(G3 in 13% and G4 in 2%). Bortezomib and melphalan dose modification was required in 6 and 2 pts, respectively. Eight pts so far have been discontinued due to toxicity related to study medication: peripheral neuropathy in 5(G2 in 1, G3 in 2 and G4 in 2), diarrhoea in 1(G3), infection in 1(G3) and prolonged thrombocytopenia in 1(G4). With a median follow up of 7 months (range:3–15), two responding pts have progressed (months +9and+10), 54(90%) are alive and 6(10%) have died. Cause of death was lung cancer diagnosed 1 month after start of study treatment(1), progressive disease(1), septic shock(2), pulmonary thromboembolism (1) and pulmonary hypertension with right ventricular insufficiency and multiorganic failure(1).

Conclusion: V-MP shows a high response rate(85% with 28%CRIF-) and manageable toxicities and could replace MP as the standard of care for elderly MM pts. An international phase 3 randomized trial is in progress to examine this.