An Efficacy and Safety Study of Bortezomib Re-treatment in Multiple Myeloma

Bortezomib will be given intravenously (into a vein) twice weekly, on Days 1, 4, 8 and 11 and then a 10-day (Days 12 to 21) rest period, of each 3-week cycle for up to a total of 8 cycles. The initial bortezomib dose is 1.0 or 1.3 milligram per meter square (mg/m\^2) depending on the previous bortezomib-based treatment, up to a maximum dose of 1.3 mg/m\^2. Participants will receive bortezomib in combination with or without dexamethasone, in accordance with the standard of care. The median total dose of dexamethasone per cycle ranges from 120 mg (Cycle 7) to 160 mg (Cycles 1 to 6 and 8).