Efficacy and safety of bortezomib in patients with plasma cell leukemia

BACKGROUND. The prognosis of patients with plasma cell leukemia (PCL), an aggressive variant of multiple myeloma (MM), is usually poor. Bortezomib is the first proteasome inhibitor approved for the treatment of advanced MM. Currently available information regarding the role of bortezomib in PCL is scanty and derives from anecdotal, single-case reports. METHODS. The authors conducted a retrospective survey of unselected Italian patients with primary or secondary PCL who were treated with bortezomib outside of clinical trials. Twelve evaluable patients were recorded who had received bortezomib for I to 6 cycles as either a single agent or variously combined with other drugs. Three patients were treated with bortezomib as frontline therapy, and 9 patients received bortezomib after 1 to 4 lines of chemotherapy, including autologous stem cell transplantation and thalidomide. RESULTS. According to the International uniform response criteria of the International Myeloma Working Group, 5 partial responses (defined as a reduction in M-protein of > 50%), 4 very good partial responses (defined as a reduction of > 90% in M-protein), and 2 complete responses (defined as negative immunofixation) were achieved, for a response rate of 92%. Responses did not appear to be influenced by previous treatments or by other clinical or biologic parameters, including chromosome 13 deletion or the combination of bortezomib with other drugs. The median progression-free and overall survivals after bortezomib were 8 months and 12 months, respectively. At the time of last follow-up, 8 patients were alive 6 to 21 months after treatment with bortezomib, 4 of whom were in very good partial or complete responses. Grade 3/4 hematologic or neurologic toxicities (graded according to the Common Terminology Criteria for Adverse Events [CTCAE; version 3]) were reported to occur in 9 patients and 1 patient, respectively, whereas 6 patients experienced possible or documented infections. CONCLUSIONS. Bortezomib appears to be an effective drug for PCL that could significantly improve the usually adverse clinical outcome of these patients.