Atrial Fibrillation and Bleeding in Patients With Chronic Lymphocytic Leukemia Treated with Ibrutinib in the Veterans Health Administration
Background: Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in adults. The introduction of novel oral agents, starting with ibrutinib in 2013, has revolutionized the therapeutic landscape; however, clinical trials have suggested an association between ibrutinib and the risk of bleeding-related adverse events and atrial fibrillation (Afib) in patients with CLL.
Methods: Patients diagnosed and treated for CLL at the Veterans Health Administration (VHA) from 2010 to 2014 were followed until December 31, 2016, death, or lack of utilization of hematology/oncology services for ≥ 18 months; or until incidence of another cancer. Treatments dispensed, evidence of VHA system use, bleeding events, and Afib were determined from the administrative records, laboratory records, pharmacy dispensation records, and clinical notes in the electronic healthcare record.
Results: From 2010 to 2014, 2,796 patients were diagnosed and received care for CLL within the VHA, of whom 172 patients received ibrutinib and 291 received bendamustine + rituximab (BR). The use of anticoagulants following induction therapy did not differ between BR and ibrutinib patients (9% vs 8%, respectively), nor did the use of antiplatelets agents (6% vs 2%, respectively). Of the 291 patients that received BR, 12 (4%) developed a bleeding event compared with 20 (12%) who received ibrutinib. Additionally, 13 (8%) ibrutinib patients developed Afib compared with 9 (3%) BR patients.
Conclusions: Real-world evidence from a nationwide cohort of patients with CLL suggests that while ibrutinib is associated with increased bleeding-related adverse events and Afib, the risk is comparable to those reported in previous clinical trials. These findings suggest that patients in real-world clinical care settings with higher levels of comorbidities may be at an increased risk for bleeding events and Afib.
Discussion
To the authors’ knowledge, this study is the first to examine the real-world incidence of bleeding and Afib in veterans who received ibrutinib for CLL in the first year of its availability. The study found minimal use of anticoagulants and/or antiplatelet agents prior to receiving first-line ibrutinib or BR, and very low use of these agents in the first 6 months following the initiation of first-line treatment. This finding suggests a high awareness among VA providers of potential adverse effects (AEs) of ibrutinib and chemotherapy, and a careful selection of patients that lack risk factors for AEs.
In patients treated with first-line ibrutinib when compared with patients treated with first-line BR, moderate increases in bleeding (2.7% vs 8.1%, P = .008) and Afib (10.5% vs 3%, P = .003) also were observed. These results are concordant with previous findings examining the use of ibrutinib in patients with CLL.18-20
Limitations
The results of this study should be interpreted with caution, as some limitations must be considered. The study was conducted in the early days of ibrutinib adoption. Since then, more patients have been treated with ibrutinib and for longer durations. As clinicians gain more familiarity and with ibrutinib, and as additional novel therapeutics emerge, it is possible that the initial awareness about risks for possible AEs may diminish; patients with high comorbidity burdens and concomitant medications would be especially vulnerable in cases of reduced physician vigilance.
Another limitation of this study stems from the potential for dual system use among patients treated in the VHA. Concurrent or alternating use of multiple health care systems (use of VHA and private-sector facilities) may present gaps in the reconstruction of patient histories, resulting in missing data as patients transition between commercial, the Centers for Medicare and Medicaid Services, and VHA care. As a result, the results presented here do not reflect instances where a patient experienced a bleeding event treated outside the VA.
Problems with missing data also may occur due to incomplete extraction from the electronic health record; these issues were addressed by leveraging an understanding of the multiple data marts within the CDW environment to harmonize missing and/or erroneous information through use of other data marts when possible. Lastly, this research represents a population-level study of the VHA, thus all findings are directly relevant to the VHA. The generalizability of the findings outside the VHA would depend on the characteristics of the external population.
Conclusion
Real-world evidence from a nationwide cohort of veteran patients with CLL treated with ibrutinib suggest that, while there is an association of increased bleeding-related events and Afib, the risk is comparable to those reported in previous studies.18-20 These findings suggest that patients in real-world clinical care settings with higher levels of comorbidities may be at a slight increased risk for bleeding events and Afib.
