[Treatment with a proteasome inhibitor, bortezomib, for thalidomide-resistant multiple myeloma].

A proteasome inhibitor with a new molecular target (PS-341: bortezomib) was recently developed, and its efficacy in the treatment of refractory multiple myeloma has been reported in the United States. Here, we present a 54-year-old Japanese male patient with refractory multiple myeloma resistant to thalidomide. In 1998, the patient was diagnosed as having multiple myeloma (IgG-kappa) and underwent chemotherapy, autologous hematopoietic cell transplantation and interferon therapy, but the disease recurred. In December 2002, thalidomide and high-dose dexamethasone therapy was initiated, and while this combination therapy was effective at first, the multiple myeloma became unresponsive. On 23 June 2003, bortezomib therapy with the following regime was therefore started: 2.2 mg (1.3 mg/m2) of bortezomib was injected intravenously on days 1, 4, 8 and 11, and after a one-week break, another cycle was performed. Starting on day 8 of the administration, the serum total protein, IgG, serum calcium and LDH levels decreased rapidly, and after day 45 of the administration, blood transfusion was no longer needed. Since this is the first report of the use of bortezomib in the treatment of refractory multiple myeloma in Japan, further monitoring of this patient will provide extremely valuable information for developing a therapy against this disease.