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CHICAGO -- Maintaining treatment with lenalidomide (Revlimid) appeared to improve overall survival among multiple myeloma patients undergoing high-dose melphalan and autologous stem cell transplantation (ASCT) versus patients who did not receive long-term therapy, researchers reported here.

At 7 years, 62% of those treated with maintenance lenalidomide had survived, compared with 50% of those in the control group (P=0.001), said of Roswell Park Cancer Institute and the State University of New York, both in Buffalo, and colleagues.

In the meta-analysis, there was a consistent benefit across subgroups of patients who were newly diagnosed with multiple myeloma, and were fit enough to undergo ASCT, they reported at the American Society of Clinical Oncology (ASCO) annual meeting.

"Lenalidomide maintenance after autologous stem cell transplantation can be considered a standard of care," McCarthy said. "We estimate that maintenance therapy extends survival 2.5 years in patients with newly diagnosed multiple myeloma following autologous stem cell transplantation. The improvements over the last decade in terms of both survival and quality of life for patients with this disease are striking, and very encouraging."

McCarthy noted that while ASCT is frequently used to treat patients with multiple myeloma, about half of these patients will later relapse or experience recurrence. Several studies have reported that ASCT can slow disease progression, but the results for overall survival (OS) had been mixed. McCarthy's group wanted to see if improvements in progression-free survival (PFS) translated to OS.

They analyzed three randomized, controlled trials conducted by the Alliance for Clinical Trials in Oncology (formerly Cancer and Leukemia Group B or CALGB) with support from the NCI, Intergroupe Francophone du Myélome (IFM), and the Gruppo Italiano Malattie Ematologiche dell'Adulto (GIMEMA).

Those trials were selected because they included a lenalidomide maintenance arm versus a control arm -- placebo or no maintenance, he explained. Also, the trials had achieved database lock for primary efficacy analysis of newly diagnosed multiple myeloma patients receiving lenalidomide after ASCT.

Those trials included 605 patients who received lenalidomide maintenance therapy and 604 patients who were controls. The median age of the patients was 58 and more than 60% were diagnosed with International Staging System (ISS) stage I or stage II multiple myeloma at baseline, while about 24% of the patients had prior lenalidomide induction.

When the researchers analyzed subgroups, they found statistically significance in favor of people younger than age 60, male patients, those who underwent prior induction therapy with lenalidomide, and in patients with ISS stage I or II, McCarthy said.

In the CALBG trial, about 24% of the patients in the study were maintained on lenalidomide for 4 years or longer; 37% were on maintenance therapy for 3 years or longer; 52% were on lenalidomide maintenance for 2 years or longer; and 67% were on lenalidomide maintenance for a year or longer. The mean duration was 30 months for lenalidomide maintenance.

In the IFM trial, 71% of patients were on lenalidomide maintenance for 1 year, while 4% were on maintenance for 4 years of longer.

McCarthy noted that one of the concerns about lenalidomide maintenance therapy is the association with second primary malignancy development, and in this analysis, there was a statistically significant increase in second malignancies among those on lenalidomide. Specifically, there was a twofold (P=0.015) increased risk of hematological second malignancies, and a 71% increased risk of a second solid malignancy (P=0.032). However, the cumulative rate of second primaries was less than 0.10% over a 7-year period, he stated.

"The overall survival benefit of lenalidomide maintenance outweighs the risk of developing a second primary malignancy," McCarthy said.

ASCO discussant of the Swedish Medical Group in Seattle said, "maintenance therapy with lenalidomide improves PFS and OS after induction and or consolidation. I think this should be considered for the majority of patients with multiple myeloma."

But Bensinger said the final chapter in the maintenance therapy story has not been written.

"I think the next step in maintenance therapy will be in the use of combination therapies, and I think ultimately we are going to select therapies based on genetic risk factors, looking at the myeloma cells," he said.

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