The use of single-agent Velcade as maintenance therapy does not significantly improve the response of multiple myeloma patients who fail to achieve a complete response following stem cell transplantation with their own cells, according to a recent study published in the journal Investigational New Drugs.

The researchers recommended that Velcade be used in combination with other myeloma treatments as maintenance therapy. “Velcade is indeed effective in the post-transplant setting, but it must be given as part of a combination therapy to realize the effects/benefits,” said Dr. Robert Rifkin from the Rocky Mountain Cancer Centers and lead investigator of the study.

Previous studies have shown that single-agent Velcade (bortezomib) is an effective treatment for relapsed and/or refractory (resistant) myeloma. Approximately 10 percent of these patients typically achieve a complete response to Velcade treatment.

Based on these results, the researchers of the current study hypothesized that maintenance therapy with Velcade may be used to treat patients who failed to achieve a complete response following treatment with high-dose melphalan (Alkeran) and autologous stem cell transplantation, in which the patient's own stem cells are collected before melphalan treatment and then transplanted back after treatment.

The researchers hoped that, as in the previous studies, 10 percent of the study participants would achieve a complete response following treatment with Velcade.

The researchers planned to enroll 68 patients who had not previously been treated with Velcade and who had failed to achieve a complete response from melphalan-based stem cell transplantation. However, they were only able to enroll 50 eligible patients, due to difficulty finding patients who had not previously been treated with Velcade.

Each patient received four 21-day cycles of Velcade maintenance (1.3 mg/m² on days 1, 4, 8, and 11). Patients were able to receive up to four additional cycles if they responded to the treatment.

Researchers found that 8.3 percent of patients achieved a complete response with Velcade maintenance therapy. This finding fell short of the hypothesized response rate of 10 percent. However, Dr. Rifkin pointed out that the response rates observed in this study were consistent with other published studies.

The researchers speculated that these low response rates might be due in part to selecting patients with an overall poor prognosis.

Physicians observed that another 2.1 percent of patients achieved a complete response, but tests could not be performed to confirm the response. In addition, 42 percent achieved a partial response, and 10 percent achieved minimal response. The rest experienced disease stabilization.

Researchers also observed that more patients who had undergone tandem (double) transplants achieved at least a partial response, as compared to single transplant patients.

At a 12-month follow up, overall survival was 95.8 percent and progression-free survival was 91.4 percent.

Treatment had to be delayed or the dose reduced in 43 percent of patients. About half of those patients discontinued treatment due to side effects of peripheral neuropathy (tingling and pain from nerve damage in limbs), low platelet counts, low white blood cell counts, or weakness.

The researchers hope that the data can help in the development of more effective combination maintenance therapies.

For more information, please read the study in the journal Investigational New Drugs (abstract).