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Introduction Bortezomib is a proteasome inhibitor used in the treatment of multiple myeloma, Waldenström’s macroglobulinemia, mantle cell lymphoma. The most reported adverse effects include fatigue, thrombocytopenia, gastrointestinal symptoms, and peripheral neuropathy, which mostly manifests as sensory neuropathic symptoms. We present a case of a patient who experienced motor neuropathy after initiating treatment with bortezomib. Case report An 87-year-old male was diagnosed with multiple myeloma and started on treatment with bortezomib, dexamethasone, and lenalidomide (VRd). After five cycles of therapy, he developed lower extremity weakness, which was severely debilitating, affecting his ability to walk, and this prompted his visit to the emergency department. Management and outcome The patient was admitted for further workup and underwent electromyography, which was consistent with demyelinating polyneuropathy with active denervation. His symptoms were attributed to bortezomib, and his VRd regimen was held. His symptoms failed to improve despite discontinuation of bortezomib. He then received steroids and intravenous immunoglobulin (IViG) with a gradual resolution of his symptoms. He was thereafter restarted on only lenalidomide and dexamethasone with no recurrence of his neuropathy. Discussion Clinicians need to be aware of the likely risk for motor neuropathy associated with bortezomib. Risk factors like older age and pre-existing neuropathy can predispose patients to this adverse effect, and clinicians should monitor for this toxicity and facilitate dose reduction or discontinuation of therapy if warranted. Sometimes, patients may also need further treatment with steroids or IVIG.

Transplant-associated thrombotic microangiopathy (TA-TMA) is a rare clinical syndrome associated with significant mortality. Although the use of plasma exchange (PE) in TA-TMA continues to be explored, evidence for its efficacy is debated. We performed a single institution, retrospective study to evaluate the efficacy of PE in treating TA-TMA patients. Special attention was given to efficacy in relation to the timing of presentation with TA-TMA since transplant. Thirty-three patients diagnosed with TA-TMA and treated with PE between January 1999 and December 2010 were included in the study. Clinical improvement was seen in eight patients (24%); four patients achieved complete resolution while the remaining four achieved partial resolution. All-cause day-30 and day-100 mortality was 33 and 55%, respectively. There was a trend toward a better outcome (complete/partial) for those presenting ≥ 100 days after transplantation (42%) vs. 100 days after transplantation (14%; P-value = 0.15). Similarly, those presenting at ≥ 100 days had better, but not significantly, 30-day and 100-day all-cause mortality rates (17 and 33%, respectively) than those presenting at 100 days (43 and 67%, respectively) (P-value = 0.25 and 0.08, for 30- and 100-day all-cause mortality, respectively). This is the first study looking at the efficacy of PE while considering the time of presentation since transplantation and is one of the largest single institution series of TA-TMA. The overall efficacy of PE is poor; however, patients who present with TA-TMA ≥100 days after transplant may have better outcome and lower mortality.

Purpose: The incidence of bone metastasis in advanced breast cancer (BrCa) exceeds 70%. Bortezomib, a proteasome inhibitor used for the treatment of multiple myeloma, also promotes bone formation. We tested the hypothesis that proteasome inhibitors can ameliorate BrCa osteolytic disease. Experimental Design: To address the potentially beneficial effect of bortezomib in reducing tumor growth in the skeleton and counteracting bone osteolysis, human MDA-MB-231 BrCa cells were injected into the tibia of mice to model bone tumor growth for in vivo assessment of treatment regimens before and after tumor growth. Results: Controls exhibited tumor growth, destroying trabecular and cortical bone and invading muscle. Bortezomib treatment initiated following inoculation of tumor cells strikingly reduced tumor growth, restricted tumor cells mainly to the marrow cavity, and almost completely inhibited osteolysis in the bone microenvironment over a 3- to 4-week period as shown by [18F]fluorodeoxyglucose positron emission tomography, micro–computed tomography scanning, radiography, and histology. Thus, proteasome inhibition is effective in killing tumor cells within the bone. Pretreatment with bortezomib for 3 weeks before inoculation of tumor cells was also effective in reducing osteolysis. Our in vitro and in vivo studies indicate that mechanisms by which bortezomib inhibits tumor growth and reduces osteolysis result from inhibited cell proliferation, necrosis, and decreased expression of factors that promote BrCa tumor progression in bone. Conclusion: These findings provide a basis for a novel strategy to treat patients with BrCa osteolytic lesions, and represent an approach for protecting the entire skeleton from metastatic bone disease. Clin Cancer Res; 16(20); 4978–89. ©2010 AACR.