Review of Efficacy and Safety Outcomes of Ibrutinib in a Veteran Population with Chronic Lymphocytic Leukemia

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BACKGROUND/RATIONALE: Chronic lymphocytic leukemia (CLL) and Small Lymphocytic Lymphoma (SLL) are indolent hematologic malignancies that account for one-quarter of all lymphomas primarily affecting older patients. Survival has improved due to the development of novel oral drugs with 85.1% 5-year survival in 2019. Ibrutinib is an oral Bruton’s tyrosine kinase inhibitor that interferes with malignant B-cell proliferation and survival. The National Comprehensive Cancer Network recommends ibrutinib as a category one treatment recommendation in all settings of CLL including relapsed/refractory disease and adverse cytogenetics. This study aims to improve clinical knowledge of ibrutinib’s efficacy and safety in a Veteran population.

OBJECTIVES: The primary objective was to determine the efficacy of ibrutinib in the Veteran population as defined by progression-free survival. Secondary objectives included overall survival, overall response, duration of therapy, and prevalence of adverse drug reactions.

METHODS: This was a single center, retrospective study conducted at the Southern Arizona VA Health Care System. A retrospective chart review of patients age 18-89 with CLL or SLL treated with ibrutinib between November 1st, 2013 to August 1st, 2019 was conducted. The Kaplan-Meier method was used to estimate overall survival and progression-free survival. Descriptive statistics was used for all other endpoints. RESULTS: Twenty-three patients were included in this study. Progression free survival and overall survival at 63 months (5.25 years) was 68.2% and 72.7%, respectively. The average duration of therapy was 20.3 months with 65.2% achieving partial response, 17.3% with stable disease, and 17.3% with progression of disease. The most common adverse events were gastrointestinal (21.7%) and cardiac (17.4%) including 3 patients who developed atrial fibrillation; 34.7% of patients required a dose reduction due to toxicity.

CONCLUSION: Use of ibrutinib in the Veteran population had similar progression-free survival as the clinical trials that led to its approval; however, slightly lower overall survival was noted compared to the clinical trials. The rate of atrial fibrillation was higher in the Veteran population compared to clinical trials, whereas the prevalence of gastrointestinal, dermatologic, neurologic, and musculoskeletal adverse events was consistent with published data.

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