Background: Bortezomib in combination with dexamethsone is administered twice a week for 2 weeks with excellent therapeutic outcome. However, in a proportion of patients it is associated with toxicities such as neuropathy and twice a week regimen is inconvenient especially in older patients. To improve convenience and compliance, we have investigated the efficacy and safety of a weekly bortezomib regimen.
Methods: We conducted a phase II multi-center single-arm study in participating Veterans Hospitals (VA) nationwide evaluating bortezomib administered at 1.6 mg/m2 IV weekly for 4 weeks with 1 week off with dexamethasone 40mg PO on the day of and day after bortezomib for upto 6 cycles in newly diagnosed multiple myeloma patients not considered for autologous stem cell transplant. The objective is to evaluate overall response rate (ORR) and toxicity of this regimen.
Results: We have enrolled all planned 50 patients (median age-71; range 50-89) at 12 VA Hospitals. Patients had significant co-morbidities including 86% with cardiovascular problems, 67% with diabetes and/or hyperlipidemia, 54% with renal dysfunction, 37% with respiratory problems, and 18% with history of cancer. All patients were on at least 5 daily medications. Of the 50 patients enrolled, 42 patients have received at least 1 cycle of therapy and were evaluable for toxicity and efficacy. With a median of 4 cycles administered, this regimen was very well tolerated. Ten patients experienced neuropathy: 6 patients experienced grade 1, two patients developed grade 2 neuropathy, while two patients who had grade 1 neuropathy at diagnosis increased to grade 2 neuropathy with pain, and the other patient increased to grade 3 neuropathy with pain, with an overall Grade 3 neuropathy rate of 2.4%.Dexamethasone dose was reduced in 30% while bortezomib dose was reduced in 10% of the patients. Additionally, grade ≥1 asthenia was observed in 52%, constipation in 38%, diarrhea in 34%, anemia in 64%, vomiting/nausea in 26%, and thrombocytopenia in 54%. Four patients have died of co-morbidities which were considered unrelated or probably unrelated to the treatment with bortezomib. Of the patients who received at least 1 cycle of therapy, 62% patients achieved ≥PR; 12% CR/nCR and an additional 14% achieved VGPR. Including MR in the analysis, ORR was observed in 90% of the evaluable patients. On intent to treat analysis including all 50 patients, ORR was observed in 76% patients and ≥ PR in 52% patients.
Conclusions: Once a week bortezomib with dexamethasone regimen is effective and well tolerated even in older patients with significant co-morbidities and should be considered as an important option in multiple myeloma.