VTE rate with abemaciclib higher in real-world setting among patients with breast cancer
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Abemaciclib resulted in an approximately twofold higher venous thromboembolism rate in a real-world setting compared with clinical trials among patients with metastatic breast cancer, according to study results published in Cancer.
Researchers also reported a significantly higher risk for death among patients who developed thrombosis.
Rationale and methods
The potential risk for VTE associated with abemaciclib (Verzenio, Eli Lilly) observed in previous clinical trials may be higher in the real-world setting, given that clinical trials select for certain patients with limited comorbidities, according to study background.
“Abemaciclib is an important therapeutic agent for patients with metastatic breast cancer but has an FDA-issued black box warning for VTE risk, which came from elevated rates of venous thrombosis reported in clinical trials,” Hanny Al-Samkari, MD, researcher in the division of hematology oncology at Massachusetts General Hospital, told Healio. “Given that thrombosis is the second most common cause of death in patients with cancer after only the malignancy itself, the rate of thrombosis in real-world populations is of paramount importance. Prior studies have shown that the rate of VTE in real-world breast cancer populations treated with palbociclib [Ibrance, Pfizer] — a related drug in the same class — is higher than those observed in the clinical trials of that drug.”
For this reason, Al-Samkari and colleagues conducted a multicenter observational cohort study that included 364 patients (median age, 61 years; 98.9% women; 87.9% white) with metastatic breast cancer who received abemaciclib. They used multivariable logistic models to assess predictors of VTE and multivariable Cox proportional hazards model to assess mortality.
VTE risk during treatment or within 30 days of treatment discontinuation served as the primary endpoint.
Median treatment duration was 5.5 months.
Key findings
According to study results, 27 patients (7.4%) developed VTE, including 17 VTE events, nine arterial thrombosis events and one patient with both. Results of multivariate modeling showed no baseline characteristics associated with increased VTE risk.
Researchers additionally found patients who developed VTE during treatment with abemaciclib had a higher risk for death compared with those who did not develop VTE (HR = 2.09; 95% CI, 1.07-4.13).
Moreover, those who developed VTE had a median survival of 9.6 months vs. 25.8 months among those who did not.
The researchers reported rates of 9.1 events per 100 person-years for VTE and 13.7 events per 100 person-years for any thrombosis during treatment with abemaciclib.
Future research
“Providers should closely consider the thrombotic risk factors of each patient they consider for abemaciclib therapy and have a low threshold to work up symptoms that could be due to thromboembolism in patients who are taking abemaciclib,” Al-Samkari told Healio. “Clinicians should also counsel patients on this risk before and during use of the drug. Studies evaluating the role of routine pharmacologic thromboprophylaxis in patients receiving abemaciclib are needed.”
For more information:
Hanny Al-Samkari, MD, can be reached at hal-samkari@mgh.harvard.edu.
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