Abstract
Substantial efficacy has been demonstrated with bortezomib-melphalan-prednisone in phase III studies in transplant-ineligible myeloma patients using various twice-weekly and once-weekly bortezomib dosing schedules. In VISTA, the regimen comprised four 6-week twice-weekly cycles, plus five 6-week once-weekly cycles. In the GIMEMA MM-03-05 study, the bortezomib-melphalan-prednisone regimen was either per VISTA ('GIMEMA twice-weekly'), or comprised nine 5-week once-weekly cycles ('GIMEMA once-weekly'). In the GEM2005MAS65 study, the regimen comprised one 6-week twice-weekly cycle, plus five 5-week once-weekly cycles. We evaluated the cumulative bortezomib dose administered during bortezomib-melphalan-prednisone, as well as efficacy and tolerability, using patient-level study data. Over all bortezomib-melphalan-prednisone cycles (nine in VISTA/GIMEMA; six in GEM2005MAS65), the median cumulative bortezomib dose administered was 38.5, 42.1, 40.3, and 32.9 mg/m(2) in VISTA, GIMEMA twice-weekly, GIMEMA once-weekly, and GEM2005MAS65, respectively, and the respective proportions of planned bortezomib dose actually delivered were 57.0%, 62.3%, 86.1%, and 90.4%. Response rates following bortezomib-melphalan-prednisone were 74-87% and appeared generally similar between studies. Three-year survival rates were 67.9-75.7% across studies. Grade 3/4 peripheral neuropathy rates were 13% in VISTA and 14% in GIMEMA twice-weekly, but were lower at 2% in GIMEMA once-weekly and 7% in GEM2005MAS65. Discontinuations and bortezomib dose reductions due to peripheral neuropathy were reduced in GIMEMA once-weekly versus VISTA and GIMEMA twice-weekly. Exclusive or predominant use of once-weekly bortezomib dosing in GIMEMA once-weekly and GEM2005MAS65 resulted in high efficacy, comparable with that demonstrated in VISTA, and similar cumulative bortezomib dose with reduced toxicity. Trials are registered with ClinicalTrials.gov: VISTA (Identifier:00111319), GIMEMA MM-03-05 (Identifier:01063179), and GEM2005MAS65 (Identifier:00443235).