SAN DIEGO – Lenalidomide, a mainstay of maintenance therapy for multiple myeloma, is now making inroads into maintenance therapy following first- and second-line therapy for chronic lymphocytic leukemia (CLL), investigators reported in two phase III studies.
Among patients with previously untreated CLL who were at high risk for early disease progression following standard chemotherapy, lenalidomide (Revlimid) maintenance therapy was associated with an 80% reduction in the relative risk for disease progression compared with placebo, reported Anna Fink, MD, of the University of Cologne, Germany, and her colleagues in the German CLL Study Group.
Similarly, lenalidomide maintenance significantly improved progression-free survival (PFS) compared with placebo among patients with CLL who had at least partial responses to second-line therapy, reported Anna Schuh, MD, of the University of Oxford, England, and her colleagues in the CONTINUUM trial.
“Lenalidomide maintenance therapy significantly improved progression-free survival, from just about 9 months to almost 40 months when given to patients with CLL who responded to second-line therapy,” Dr. Schuh said at the American Society of Hematology annual meeting.
Both studies were unblinded because of the superiority of lenalidomide after prespecified analyses, on the recommendation of the respective data safety monitoring boards (DSMBs).
The PFS advantage with lenalidomide seen in each study did not translate into differences in overall survival in either study, however.
Maintenance after first-line therapy
In the CLLM1 trial, Dr. Fink and her colleagues enrolled physically fit, previously untreated patients with CLL and delivered chemoimmunotherapy at the investigator’s choice: either FCR (fludarabine, cyclophosphamide, and rituximab), FR (fludarabine and rituximab), FC (fludarabine and cyclophosphamide), or BR (bendamustine and rituximab).
Patients who had at least a partial response after a minimum of four cycles were identified as being at high risk for progression if they had minimal residual disease (MRD) levels of at least 10-2 cells, or MRD levels from 10-4 to less than 10-2 combined with either an unmutated IGHV gene status, del(17p) or TP53 mutation at baseline.
Of 468 screened patients, 89 were deemed to have high risk disease, and these patients were randomly assigned on a 2:1 basis to maintenance with lenalidomide given 5 mg orally for the first cycle and escalated to a target dose of 15 mg by the seventh cycle, or to placebo.
Additional dose escalations could be performed based on MRD assessments every 6 months, with the drug continued until progression or unacceptable toxicity. Patients also were assigned to daily low-dose aspirin or to an anticoagulation agent depending on their individual risk for thromboembolic events.
The study was stopped and unblinded after a planned interim analysis showed that the difference in PFS met the stopping boundary for efficacy.
Ultimately, 56 patients assigned to lenalidomide received study treatment, as did 29 assigned to placebo.
At a median follow-up of 17.5 months, the median PFS according to independent review was not reached for lenalidomide, vs. 13.3 months for placebo. Lenalidomide was associated with a hazard ratio (HR) for progression of 0.148 (P less than .00001), and a relative risk reduction of 80%.
Lenalidomide was also significantly better for PFS in analysis by MRD at baseline, with a PFS of 19.4 months for placebo vs. not reached among patients with less than 10-2 but more than 10-4 cells (HR, 0.125) and 3.7 vs. 32.3 months, respectively, for patients with MRD greater than 10-2 (HR 0.165).
There were three deaths (two in patients on placebo), and at the last analysis there was no difference in overall survival. In all, 42.9% of patients on lenalidomide discontinued because of adverse events, compared with 72.4% of those on placebo.
Maintenance after second-line therapy
In CONTINUUM, patients with at least a partial response after two prior lines of therapy and an Eastern Cooperative Oncology Group performance score of 0-2 were enrolled and randomized to receive either lenalidomide (160 patients) at a starting dose of 2.5 mg/day for the first 28-day cycle, 5 mg/day from cycle 2, and, if well tolerated, up to 10 mg/day from cycle 7 on, or to placebo (154 patients).
This study, as noted before, was also unblinded at the time of the primary analysis as recommended by the DSMB, after a prespecified number of events had occurred.
At a median follow-up of 31.5 months, the median PFS, a co-primary endpoint with OS, was 33.9 months in the lenalidomide arm, compared with 9.2 months in the placebo arm, translating into a HR for lenalidomide of 0.40 (P less than .001).
The lenalidomide advantage also was seen in a subgroup analysis by age, prior response to chemotherapy, and number of factors for poor prognosis. Of note, among patients older than age 70, the PFS with lenalidomide was 52.5 months, compared with 7.3 months for placebo (HR 0.34, P = .005).
In a second PFS analysis conducted after 71 months of follow-up, lenalidomide remained superior, with a median PFS of 57.5 months vs. 32.7 months in the placebo arm. As noted, there was no difference in overall survival in this study.
Grade 3 or greater adverse events occurring more frequently with lenalidomide were neutropenia, thrombocytopenia, diarrhea, pneumonia, fatigue, hypokalemia, pulmonary embolism, and sepsis. There was no difference in the incidence of second primary malignancies, however.
CLLM1 was sponsored by the German CLL Study Group with support from Celgene. CONTINUUM was supported by Celgene. Dr. Fink disclosed research funding from the company, and travel grants and honoraria from others. Dr. Schuh disclosed honoraria from and consulting with Celgene and other companies.