Atrial fibrillation (AFib) is a known and serious side effect of some cancer treatments, but it is underreported in cancer drug trials, French investigators said in a new report.
As a result, oncologists likely underestimate the risk of atrial fibrillation when new cancer drugs come to market, they said.
The team came to these conclusions after conducting a meta-analysis of 191 phase 2 or 3 clinical trials that included 26,604 patients. The trials investigated 15 anticancer drugs used as monotherapy.
The meta-analysis showed that the annualized incidence rate of AFib ranged from 0.26 cases per 100 person-years – about the same as placebo – to 4.92 cases, a nearly 20 times’ higher risk.
Rates were the highest for ibrutinib, clofarabine, and ponatinib.
The study was published in JACC: CardioOncology, a journal of the American College of Cardiology.
Actual rates of AFib are probably higher than what they found in this meta-analysis, the authors suspect, because most oncology trials only identify and report severe cases of AFib that require immediate medical attention. Less severe cases can also lead to serious complications, including strokes, but they go unreported, said the investigators, led by Joachim Alexandre, MD, PhD, a member of the cardio-oncology program at the University of Caen Normandie Hospital Center, France.
“These findings suggest a global and systemic underreporting and/or underidentification of cardiotoxicity among cancer clinical trial participants,” and AFib reporting is “particularly affected,” they said.
Call for routine monitoring
The root of the problem is the lack of routine rhythm monitoring in cancer trials. This in turn “leads to a significant underestimation of AFib incidence” and rates “markedly lower than those observed among real-life” patients, the authors pointed out.
To address the issue, Dr. Alexandre and his team called for routine cardiac monitoring in trials to capture the true incidence of AFib and to “clearly define which anticancer drugs are significantly associated” with the condition.
Approached for comment, Michael G. Fradley, MD, medical director of cardio-oncology at the University of Pennsylvania, Philadelphia, agreed.
“It’s incredibly important” to “identify the drugs most likely to cause arrhythmias and determine the best prevention and treatment strategies. Unfortunately, systematic evaluation of arrhythmias in cancer clinical trials has often been lacking,” Dr. Fradley told this news organization.
The investigators said the issue is particularly pressing for drugs known to be associated with AFib. For Bruton’s tyrosine kinase inhibitors such as ibrutinib, for instance, they call for standardize AFib detection in trials “not only on 12-lead ECGs” for symptomatic AFib but also with “longer-term ambulatory monitoring or insertable cardiac monitors to detect subclinical AFib.”
Dr. Fradley said there might also be a role for newer wearable technologies that can detect arrhythmias through a skin patch or by other means.
Details of the meta-analysis
The investigators pulled the 191 studies they used in their meta-analysis from the ClinicalTrials.gov database.
The trials covered anticancer drugs used as monotherapy up to Sept. 18, 2020. Almost half were randomized trials, but only seven had placebo arms. Trials involving hematologic cancers outnumbered those involving solid tumors.
The 15 drugs examined were dacarbazine, abiraterone, clofarabine, azacitidine, ibrutinib, nilotinib, ponatinib, midostaurin, ipilimumab, aldesleukin, lenalidomide, pomalidomide, rituximab, bortezomib, and docetaxel.
The annualized incidence AFib rates per 100 person-years were 4.92 cases for ibrutinib, 2.38 cases for clofarabine, and 2.35 cases for ponatinib.
The lowest AFib rates were for ipilimumab (0.26 cases), rituximab (0.27), and nilotinib (0.29).
For placebo, the annualized rate was 0.25 cases per 100 person-years.
The team said caution is warranted regarding their estimations for clofarabine and midostaurin (0.65 cases) because no trials were registered after September 2009, when adverse event reporting became mandatory. As a result, estimates may be artificially low.
One of the limits of the study is that it focused on monotherapy in an age when combination treatment is generally the rule for cancer, the authors noted.
No external funding was reported for the study. Dr. Alexandre has received honoraria for presentations and consulting fees from Bayer, BMS, Pfizer, Amgen, and Bioserenity.
A version of this article first appeared on Medscape.com.