SAN DIEGO – Patients with chronic lymphocytic leukemia at risk for early relapse were about 85% less likely to progress on lenalidomide maintenance therapy compared with placebo, based on an interim analysis of the randomized phase III CLLM1 study.
After a typical follow-up time of 17.5 months, median durations of progression-free survival were not reached with lenalidomide and were 13 months with placebo, for a hazard ratio of 0.15 (95% confidence interval, 0.06-0.35).were “statistically significant, robust, and reliable in favor of lenalidomide,” , said at the 2016 meeting of the American Society of Hematology. Several patients in the lenalidomide arm also converted to minimal residual disease (MRD) negativity, added Dr. Fink of University Hospital Cologne (Germany).
Theincluded patients whose CLL responded at least partially to front-line chemoimmunotherapy, but who were at high risk of progression – minimal residual disease levels were at least 10–2, or were between 10–4 and 10–2 in patients who also had an unmutated IGHV gene status or del(17p) or TP53 mutations at baseline. Among 89 patients who met these criteria, 60 received lenalidomide maintenance and 20 received placebo.
The initial lenalidomide cycle consisted of 5 mg daily for 28 days. To achieve MRD negativity, clinicians increased this dose during subsequent cycles to a maximum of 15 mg daily for patients who were MRD negative after cycle 12, 20 mg for patients who were MRD negative after cycle 18, and 25 mg for patients who remained MRD positive. Median age was 64 years, more than 80% of patients were male, and the median cumulative illness rating was relatively low at 2, ranging between 0 and 8.
A total of 37% of patients had a high MRD level and 63% had an intermediate level. For both cohorts, lenalidomide maintenance significantly prolonged progression-free survival, compared with placebo, with hazard ratios of 0.17 and 0.13, respectively. Patients received a median of 11 and up to 40 cycles of lenalidomide, but a median of only 8 cycles of placebo.
In all, 43% of lenalidomide patients and 72% of placebo patients stopped maintenance. Nearly a third of those who discontinued lenalidomide did so because of adverse events, but 45% of patients who stopped placebo did so because of progressive disease, Dr. Fink said. Lenalidomide was associated with more neutropenia, gastrointestinal disorders, nervous system disorders, and respiratory and skin disorders than was placebo, but the events were usually mild to moderate in severity, she added.
The three deaths in this study yielded no treatment-based difference in rates of overall survival. Causes of death included acute lymphoblastic leukemia (lenalidomide arm), progressive multifocal leukoencephalopathy (placebo), and Richter’s syndrome (placebo). Venous thromboembolic events were uncommon because patients were given low-dose aspirin or anticoagulant therapy, Dr. Fink noted.
“Lenalidomide is a feasible and efficacious maintenance option for high-risk CLL after chemoimmunotherapy,” she concluded. The low duration of progression-free survival in the placebo group confirms the prognostic utility of assessing risk based on MRD, which might be useful in future studies, she added.
The German CLL Study Group sponsored the trial. Dr. Fink disclosed ties to Mundipharma, Roche, Celgene, and AbbVie.