Certain cancer treatments can damage the cardiovascular system, causing side effects such as high blood pressure, abnormal heart rhythms and heart failure. But many studies of treatments for late-stage cancer have a critical blind spot: Only 62% even attempted to report any cardiovascular disease (CVD)–related health events, MedPage Today reports. And those that did look for those kinds of side effects might have systematically underreported them.  

Daniel Addison, MD, of the Ohio State University Medical Center, and colleagues analyzed data from 189 Phase II and III trials of cancer drugs ultimately approved by the Food and Drug Administration (FDA). The trials were conducted between 1998 and 2018.

The study authors were primarily looking at the reporting of major adverse cardiovascular events (MACE), which included the diagnosis of myocardial infarction (heart attack), stroke, heart failure, coronary revascularization, atrial fibrillation or CVD-related death. They also looked for any reports of CVD-related health events. They published their findings in the Journal of the American College of Cardiology.

The trials enrolled 97,365 people, who had an average age of 58. Forty-six percent of the cohort was female, and 73% took a biologic, targeted or immune-based cancer treatment. They were followed for 148,138 cumulative years of follow-up or a median follow-up of 30 months for each person.

During that time, the participants in the 62% of studies that reported CVD-related outcomes experienced 1,148 cases of MACE, including 375 cases of heart failure, 253 cases of myocardial infarction, 180 cases of stroke, 65 cases of atrial fibrillation, 29 revascularizations and 246 CVD-related deaths.

Those who received active treatment had nearly twice as many adverse events compared to taking placebos: There were 792 cases of MACE in the treatment arms of the studies versus 356 cases in the control arms. There was no association between reporting CVD-related health events and the efficacy of the cancer drugs.

Overall, the rate of cardiovascular issues in those studies was less than in the general population for that age group. “Among pivotal clinical trials linked to contemporary FDA-approved cancer drugs, reported CVD event rates trail expected population rates,” the study authors concluded. Nanette Bishopric, MD, and Marc Lippman, MD, both of the Georgetown Lombardi Comprehensive Cancer Center in Washington, DC, wrote in an accompanying editorial that the difference between the reported MACE rates and what would be expected of this population "is quite a large discrepancy.”

This findingis most likely a reflection of a serious failing in these studies, the authors note: Many cancer trials deliberately exclude people who have any cardiovascular issues, such as high blood pressure. But in the real world, many people with cancer also have cardiovascular issues, so it’s particularly important to understand cardiovascular side effects. The authors recommend that future clinical trials be designed to deliberately include more people with cardiovascular risk factors and heart disease to understand the real-world effects of these treatments.

"The present study,” they continued, “points to an urgent need to collect data to establish the true cardiovascular risks associated with cancer chemotherapy and to help with planning appropriate treatment practices.”

To read the MedPage Today article, click here.

To read the study abstract, click here.

To read the editorial abstract, click here.

For related coverage, see “Heart Disease and Stroke Are Major Killers of People With Cancer.”