The addition of an angiotensin-converting enzyme (ACE) inhibitor did not decrease risk for chemotherapy-related cardiac damage in patients being treated for breast cancer and non-Hodgkin lymphoma (NHL), a new randomized trial showed.
The results suggested adding an ACE inhibitor doesn't affect cardiac injury or cardiac function outcomes "and should not be used as a preventative strategy" in these patients, David Austin, MD, consultant cardiologist, Academic Cardiovascular Unit, The James Cook University Hospital, Middlesbrough, England, and chief investigator for the PROACT study, told theheart.org | Medscape Cardiology.
But while these negative results are disappointing, he said, "we now have a definitive result in a robustly conducted trial that will take the field forward."
The findings were presented on April 8, 2024, at the American College of Cardiology (ACC) Scientific Session 2024.
Anthracyclines, which are extracted from Streptomyces bacterium, are chemotherapy drugs widely used to treat several types of cancer. Doxorubicin is among the most clinically important anthracyclines.
While extremely effective, anthracyclines can cause irreversible damage to cardiac cells and ultimately impair cardiac function and even cause heart failure, which may only be evident years after exposure. "Cardiac injury is very common in patients treated with high dose anthracyclines," noted Austin.
The open-label PROACT study included 111 adult patients, mean age 58 years and predominantly White and women, being treated for breast cancer (62%) or NHL (38%) at National Health Service hospitals in England with high-dose anthracycline-based chemotherapy.
Patients were randomized to standard care (six cycles of high-dose doxorubicin-equivalent anthracycline-based chemotherapy) plus the ACE inhibitor enalapril maleate or standard care alone. The mean chemotherapy dose was 328 mg/m2; any dose greater than 300 is considered high.
The starting dose of enalapril was 2.5 mg twice a day, which was titrated up to a maximum of 10 mg twice a day. The ACE inhibitor was started at least 2 days before chemotherapy began and finished 3 weeks after the last anthracycline dose.
During the study, enalapril was titrated to 20 mg in more than 75% of patients, with the mean dose being 17.7 mg.
Myocardial Injury Outcome
The primary outcome was myocardial injury measured by the presence (≥ 14 ng/L) of high sensitivity cardiac troponin T (cTnT) during anthracycline treatment and 1 month after the last dose of anthracycline.
cTnT is highly expressed in cardiomyocytes and has become a preferred biomarker for detecting acute myocardial infarction and other causes of myocardial injury.
Blood sampling for cTnT and cardiac troponin I (cTnI) was performed at baseline, within 72 hours prior to chemotherapy and at trial completion. All patients had negative troponin results at baseline, indicating no heart damage.
A majority of patients experienced elevations in troponin (78% in the enalapril group and 83% in the standard of care group), but there was no statistically significant difference between groups (adjusted odds ratio [OR], 0.65; 95% CI, 0.23-1.78; P = .405).
There was also no significant difference between groups in terms of cTnI, a secondary endpoint. However, the proportion of patients testing positive for cTnI (47% in the enalapril group and 45% in controls) was substantially lower than that for cTnT.
Large Discrepancy
The "large discrepancy in the rate of injury" with cTnT "has implications for the clinical interpretation of cardiac biomarkers in routine practice, and we should proceed with caution," Austin told theheart.org | Medscape Cardiology.
The finding has implications because guidelines don't currently differentiate based on the type of troponin, Austin said in a press release. "I was surprised by the difference, and I think this raises the question of what troponin we should be using."
Secondary outcomes focused on cardiac function, measured using echocardiography and included left ventricular global longitudinal strain (LVGLS) and left ventricular ejection fraction (LVEF). These were measured at baseline, 4 weeks after the last anthracycline dose and 1 year after the final chemotherapy.
There was no between-group difference in LVGLS cardiac function (21% for enalapril vs 22% for standard of care; adjusted OR, 0.95; 95% CI, 0.33-2.74; P = .921). This was also true for LVEF (4% for enalapril vs 0% for standard of care group; adjusted OR, 4.89; 95% CI, 0.40-674.62; P = .236).
Asked what the research team plans to do next, Austin said "the immediate first step" is to continue following PROACT patients. "We know heart failure events and cardiac dysfunction can occur later down the line."
Due to the challenge of enrolling patients into trials like PROACT, "we should come together as a sort of a broader cardiovascular/oncology academic community to try to understand how we can better recruit patients into these studies," said Austin.
"We need to solve that problem before we then go on to maybe examine other potential preventative therapies."
He doesn't think an alternative ACE inhibitor would prove beneficial. "We need to look elsewhere for effective therapies in this area."
He noted these new findings are "broadly consistent" with other trials that investigated angiotensin receptor blockers.
Tough Population
Commenting on the study during a media briefing, Anita Deswal, chair, medicine, Department of Cardiology, Division of Internal Medicine, The University of Texas, commended the researchers for managing to enroll patients with cancer as this is "a tough" population to get to agree to being in a clinical trial.
"These patients are often overwhelmed financially, physically, and emotionally with the cancer diagnosis, as well as the cancer therapy and, therefore, to enroll them in something to prevent, maybe, some potential cardiac toxicity down the line, is really hard."
Past trials investigating neuro-hormonal blockers to prevent cardiotoxicity have been criticized for enrolling patients at "too low risk," said Deswal. "But investigators here went that step beyond and enrolled patients who were going to receive higher doses of anthracyclines, so kudos to that."
And she noted investigators managed to get patients on almost the maximum dose of enalapril. "So, the drug was poised to have an effect — if it was there."
The negative results may have something to do with endpoints. "Maybe we haven't quite figured out what are the cutoffs for high sensitivity troponin I that identify patients truly at risk" of developing heart failure in the future.
Commenting on the study for theheart.org | Medscape Cardiology, Anu Lala, MD, assistant professor of medicine at the Icahn School of Medicine at Mount Sinai, New York City, said the results may come as a surprise to some.
"ACE inhibitors are considered cardioprotective and for this reason are often used prophylactically in patients receiving chemotherapy."
Lala agrees troponin may not be the right endpoint. "Another question is whether clinical outcomes should be followed in addition to symptoms or onset of any heart failure symptoms, which may hold greater prognostic significance."
The study was funded by the National Institute for Health and Care Research.