The Bruton tyrosine kinase inhibitor ibrutinib has been linked to an almost 20-fold increased risk of major bleeding in blood cancer patients taking concomitant antiplatelet and anticoagulation therapy in a clinical setting.
Caution should be used when weighing the risks and benefits of ibrutinib for patients already taking antiplatelet or anticoagulation therapy, or both, wrote Paul R. Kunk, MD, of University of Virginia, Charlottesville, and his colleagues. Their report is in.
Ibrutinib had been associated with an increased risk of bleeding, albeit low, in the clinical trial setting but the authors suggested that this rate could be higher in everyday clinical practice.
“Much of the information [from clinical trials] on the bleeding risk with ibrutinib, included pooled analyses, was from patients exclusively treated in clinical trials with specific exclusion criteria. These criteria have generally excluded patients with significant comorbidities. However, these patients are seen in clinical practice,” the researchers wrote.
They conducted a review of patients attending their center and associated regional clinics between January 2012 and May 2016. They identified 70 patients, average age 72, who were taking ibrutinib for chronic lymphocytic leukemia (64%) and mantle cell lymphoma (27%), diffuse large B-cell lymphoma (4%), lymphoblastic lymphoma (3%), and Waldenström macroglobulinemia (1%).
The analysis showed that bleeding of any grade occurred in 56% of patients, mostly grade 1-2 bruising and epistaxis. However, major bleeding, defined as grade 3, occurred in 13 patients (19%), a figure that the authors noted was greater than the rate of around 7% reported by clinical trials.
Of these patients, seven were taking combined antiplatelet and anticoagulant therapy, four were taking antiplatelets alone, one was taking an anticoagulant agent alone, and one was taking only ibrutinib.
Univariate analysis showed that the factors associated with an increased risk of major bleeding included antiplatelet or anticoagulant medication, the combination of the two medications or interacting medications, anemia (hemoglobin less than 12 g/dL) and an elevated international normalized ratio (greater than 1.5).
However, in a multivariate analysis, only combined antiplatelet and anticoagulant use (hazard ratio, 20.0; 95% confidence interval, 2.1-200.0; P less than .01) and an elevated INR (HR, 4.6; 95% CI, 1.1-19.6; P less than .01) remained statistically significant.
The researchers said the risk of major bleeding in patients taking both antiplatelet and anticoagulant therapy was “unacceptably high” and “medications other than ibrutinib should be considered” in this patient population.
Overall, they said their findings confirmed “the increasingly recognized risk of major bleeding complications with ibrutinib compared with what was originally reported in the clinical trial setting.
“As ibrutinib increases in use, it is paramount to increase awareness of the known adverse events. This is especially important given the association of ibrutinib use with atrial fibrillation,” they wrote.
They noted that their trial was limited by the relatively small population size. Their finding that platelet count was not associated with bleeding risk was also “counterintuitive,” they noted.
SOURCE: Kunk PR et al. Clin Lymphoma Myeloma Leuk. 2018 Jul 15. doi: 10.1016/j.clml.2018.07.287.