Long-Term Follow-Up Shows BTK Inhibitor Produces Deep, Durable Responses in CLL
Treatment with a BTK inhibitor has been shown to yield good depth and duration of response in patients with chronic lymphocytic leukemia (CLL), regardless of TP53 status.
Patients with CLL often receive chemoimmunotherapy, which may lead to high rates of remission. However, these patients are still faced with high rates of relapse—especially among those with TP53 mutations—and adverse events that reduce the effectiveness of treatment. Prior studies have indicated that single-agent ibrutinib may be a therapeutic alternative to chemoimmunotherapy, but further research is needed to confirm this approach.
Inhye E Ahn, MD, National Institute of Health (Bethesda, MD), and colleagues conducted a long-term follow-up study of an open-label phase II trial, in which researchers enrolled 86 patients with CLL regardless of treatment history to receive ibrutinib (420 mg once daily). Patients were stratified into a TP53 aberration cohort (n = 51) or an older patient cohort (n = 35).
Results of the study were published in Blood (online February 26, 2018; doi:10.1182/blood-2017-12-820910).
Researchers reported that after a median follow-up of 4.8 years, 57% of patients remained enrolled in the study. The overall response rate at 6 months was 95.8% in the TP53 cohort compared with 93.9% in the older patient cohort. Additionally, researchers observed that the depth of response to ibrutinib deepened over time; 29% of patients in the TP53 cohort and 27.3% of patients in the older cohort had a complete response.
The estimated 5-year progression-free survival (PFS) rate was reportedly 74.4% in treatment-naïve patients with TP53 aberration compared with 19.4% among patients with relapsed or refractory disease in the same cohort. Similarly, the 5-year overall survival (OS) rate was 85.3% and 53.7%, respectively.
In the older patient cohort, the 5-year PFS rate was 64.8% among patients with relapsed or refractory disease while the 5-year OS rate was 71.6% for the same patients.
Researchers reported no PFS or OS events for treatment-naïve older patients.
Importantly, the safety profile of ibrutinib in CLL remained consistent with previous findings, which led researchers to conclude that long-term administration of ibrutinib is well-tolerated and provides durable disease control for most patients in this population.—Zachary Bessette