For patients with relapsed/refractory chronic lymphocytic leukemia (CLL), long-term treatment with the phosphoinositol 3-kinase inhibitor idelalisib appears safe and effective, according to investigators.
Final results from a phase 3 trial confirmed survival advantages when idelalisib is used in combination with rituximab, reported lead author Jeff P. Sharman, MD, of Willamette Valley Cancer Institute and Research Center in Springfield, Ore., and colleagues.
During follow-up, which exceeded 5 years in some patients, no new idelalisib-related adverse events were encountered, supporting the safety of long-term use, the investigators noted. The report is in the Journal of Clinical Oncology.
This study was “pivotal” for treating elderly patients with relapsed CLL, the investigators wrote, as these patients previously had few treatment options beyond supportive or palliative care.
Earlier results from the study showed that adding idelalisib to rituximab raised overall response rates from about 15.5% to 83.6% and median progression-free survival from 6.5 months to 19.4 months, resulting in “significantly better clinical outcomes compared with those seen with rituximab alone,” leading to approval by the Food and Drug Administration.
During the primary study, 110 patients received a combination of idelalisib and rituximab, while 108 patients received rituximab and placebo. The median patient age was 71 years, with a median of three lines of prior therapy. The present analysis focused on the 110 patients in the combination group who received at least one dose of idelalisib, whether or not they elected to participate in the extension phase.
After a median follow-up of 18 months, ranging from 0.3 months to 67.6 months, the overall response rate was 85.5% and the median progression-free survival was 20.3 months, both of which are similar to earlier findings. Median overall survival was 40.6 months.
With a median duration of exposure of 16.2 months, the safety analysis revealed no new idelalisib-related adverse events.
However, the investigators pointed out that prolonged therapy often led to diarrhea, which ultimately occurred in about half of patients (46.4%). Roughly equal amounts of patients experienced grade 2 (17.3%) or grade 3 or greater diarrhea (16.4%). In cases of grade 3 or greater diarrhea, steroid therapy was recommended, typically resulting in symptom resolution within 2 weeks; however, “there were insufficient numbers of patients to determine if steroid therapy affected the duration of symptoms,” the investigators wrote.
“The longer-term data presented here confirm the previously reported efficacy of targeting PI3K with idelalisib in patients with relapsed/refractory CLL and support the use of [idelalisib and rituximab] in this patient population with careful management of potential [adverse events],” they wrote.
Gilead Sciences funded the study. Dr. Sharman reported financial relationships with Gilead and other companies.
SOURCE: Sharman JP et al. J Clin Oncol. 2019 Apr 17. doi: 10.1200/JCO.18.01460.
