EDINBURGH – Lenalidomide maintenance therapy after chemoimmunotherapy in high-risk chronic lymphocytic leukemia (CLL) improved progression- and event-free survival, but not overall survival, and was associated with three unexpected cases of B-cell acute lymphoblastic leukemia (B-ALL), according to 4-year follow-up in the German, phase 3 CLLM1 study.
Given these findings, and in particular the B-ALL cases, lenalidomide cannot be generally recommended as maintenance therapy in high-risk CLL, Moritz Fürstenau, MD, of the University of Cologne, reported in a poster at the International Workshop on Chronic Lymphocytic Leukemia.
At a median follow-up of 47.6 months, median progression-free survival (PFS) by investigator assessment was 54.7 months in 60 patients randomized to receive lenalidomide maintenance therapy, compared with 23.2 months for 29 who received placebo (hazard ratio, 0.22), and median event-free survival (EFS) was 46.2 months vs. 14.6 months in the groups, respectively (hazard ratio, 0.24), Dr. Fürstenau said during an oral poster presentation at the conference.
“So ... after 4 years of observation, we still see improvement in PFS, EFS, and time to next treatment,” he said, also noting that minimal residual disease (MRD) negativity was achieved by eight patients in the lenalidomide group, and in none of the patients in the placebo group.
However, overall survival was 79% and 87% in the lenalidomide and placebo groups, respectively (HR, 1.53). In total, 12 patients died, including 9 in the lenalidomide group from fatal infections, concomitant disease, CLL progression, or unknown causes. Three patients in the placebo group died from CLL progression or fatal infection.
In the lenalidomide group, hematological and solid tumor second primary malignancies were reported in three and four patients, respectively (5% and 7%), compared with zero and two patients, respectively (0% and 7%), in the placebo group.
The CLLM1 study of the German CLL Study Group evaluated maintenance with lenalidomide vs. placebo in patients with high risk of progression after first-line chemoimmunotherapy. Previously reported results also favored lenalidomide maintenance for PFS, but not OS, Dr. Fürstenau said, adding that the study was unblinded at a median follow-up of 17.9 months, and in November 2017 treatment was stopped when two cases of B-ALL were observed. A third case was reported in 2018.
The current analysis includes data available through December 2018, and the findings warrant further investigation to analyze the unexpectedly high incidence of B-ALL, he said.
The CLLM1 study was funded by Celgene.