Successful treatment with a modified bortezomib schedule of weekly and longer intervals for patients with refractory/resistance multiple myeloma

Bortezomib is a potent agent for multiple myeloma (MM); however, severe treatment-related toxicities such as peripheral neuropathy have been observed in conjunction with its use. In this study, we present the cases of 9 patients with refractory MM whose administration schedule was modified from twice weekly to an interval of once weekly or longer mainly due to adverse events. The average duration from diagnosis to the time of bortezomib induction was 56 months. The schedule was changed to the modified administration according to the physician's discretion. The average duration of modified treatment was 16 months. Six patients with IgG or IgA subtype showed more than a minor response. One patient with BJP had stable disease for 3 years, and the other BJP-type patient with extramedullary plasmacytomas showed remarkable tumor regression. The treatment-related toxicities of this strategy were mild and tolerable. To our knowledge, this is the first report of the administration of bortezomib at intervals longer than once weekly.