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In reviewing 4 clinical trials of ibrutinib, researchers found that a quarter of chronic lymphocytic leukemia (CLL) patients discontinued treatment with the Bruton tyrosine kinase (BTK) inhibitor.
Ten percent of patients stopped taking the drug due to disease progression, and 15% stopped because of adverse and medical events.
Sequencing data indicated that mutations in BTK and PLCG2 were associated with CLL progression but not Richter’s transformation (RT).
Jennifer A. Woyach, MD, of Ohio State University in Columbus, and her colleagues detailed these discoveries in JAMA Oncology.
The researchers evaluated 308 patients participating in 4 trials conducted at a single institution. The team described the characteristics and outcomes of the patients who discontinued treatment with ibrutinib.
At a median follow-up of 20 months, 232 of the patients studied (75%) remained on therapy, including 7 patients who went off study to undergo stem cell transplant or receive ibrutinib commercially at another center.
Forty-five patients (15%) discontinued treatment following adverse or medical events—28 due to infection, 8 for other adverse events, and 9 due to other medical events. This included 2 patients who needed anticoagulation, 2 with comorbid medical conditions, 1 case of progressive multifocal leukoencephalopathy in a patient who had received rituximab, 1 case of noncompliance, 1 failure to thrive, 1 sudden cardiac death, and 1 cerebrovascular event.
Thirty-one patients (10%) discontinued treatment due to disease progression. Progression included RT or progressive CLL. RT appeared to occur early and CLL progression later. The median survival was 3.5 months after RT and 17.6 months after CLL progression.
Deep sequencing performed on 11 patients with CLL progression revealed BTK or PLCG2 mutations in all of them. But sequencing data on peripheral blood from 8 patients with RT showed that only 2 patients had mutations in BTK, and a lymph node sample showed no mutations in BTK or PLCG2.
