Single-agent ibrutinib has had sustained efficacy and a rate of complete response that has increased over time, according to a 5-year follow-up report including 132 patients with chronic lymphocytic leukemia (CLL).
Efficacy has been maintained in both treatment-naive and relapsed/refractory CLL, despite the presence of high-risk genomic features in many patients, investigators reported in Blood.
Treatment has been well tolerated, and the occurrence of severe adverse events has diminished over time, according to Susan M. O’Brien, MD, of the Chao Family Comprehensive Cancer Center, University of California, Irvine, and her colleagues.
“The safety profile of ibrutinib over time remains acceptable and manageable, allowing almost one-half of the patients (48%) to be treated for more than 4 years and thus maximize response,” the investigators wrote.
The report was based on 5-year follow-up of patients with CLL who had been enrolled in a phase 1b/2 study (PCYC-1102) and an extension study (PCYC-1103). A total of 132 patients were evaluated, including 101 with relapsed/refractory disease and 31 who were treatment naive.
The overall response rate remained high, at 89% in this 5-year follow-up. Complete response rates increased over time, reaching 29% in treatment-naive patients and 10% in relapsed/refractory patients. In a previous report on 3-year follow-up for these patients, investigators reported complete response rates of 23% in the previously untreated group and 7% in the relapsed/refractory group. The new findings demonstrate “deepening of responses” with continued ibrutinib therapy, Dr. O’Brien and her coauthors wrote.
The 5-year rate of progression-free survival was 44% for relapsed/refractory patients and 92% for treatment-naive patients in this study. Median progression-free survival was 51 months for the relapsed/refractory cohort. “[Progression-free survival] with single-agent ibrutinib in [treatment-naive] patients appears particularly favorable, because the median has not been reached,” investigators wrote.