The first global trial to compare the cardiovascular (CV) safety of two therapies for prostate cancer proved inconclusive because of inadequate enrollment and events, but the study is a harbinger of growth in the emerging specialty of cardio-oncology, according to experts.
“Many new cancer agents have extended patient survival, yet some of these agents have significant potential cardiovascular toxicity,” said Renato D. Lopes, MD, in presenting a study at the annual congress of the European Society of Cardiology.
In the context of improving survival in patients with or at risk for both cancer and cardiovascular disease, he suggested that the prostate cancer study he led could be “a model for interdisciplinary collaboration” needed to address the relative and sometimes competing risks of these disease states.
This point was seconded by several pioneers in cardio-oncology who participated in the discussion of the results of the trial, called PRONOUNCE.
“We know many drugs in oncology increase cardiovascular risk, so these are the types of trials we need,” according Thomas M. Suter, MD, who leads the cardio-oncology service at the University Hospital, Berne, Switzerland. He was the ESC-invited discussant for PRONOUNCE.
More than 100 centers in 12 countries involved
In PRONOUNCE, 545 patients with prostate cancer and established atherosclerotic cardiovascular disease were randomized to degarelix, a gonadotropin-releasing hormone antagonist, or leuprolide, a GnRH agonist. The patients were enrolled at 113 participating centers in 12 countries. All of the patients had an indication for an androgen-deprivation therapy (ADT).
In numerous previous studies, “ADT has been associated with higher CV morbidity and mortality, particularly in men with preexisting CV disease,” explained Dr. Lopes, but the relative cardiovascular safety of GnRH agonists relative to GnRH antagonists has been “controversial.”
The PRONOUNCE study was designed to resolve this issue, but the study was terminated early because of slow enrollment (not related to the COVID-19 pandemic). The planned enrollment was 900 patients.
In addition, the rate of major adverse cardiovascular events (MACE), defined as myocardial infarction, stroke, or death, was lower over the course of follow-up than anticipated in the study design.
No significant difference on primary endpoint
At the end of 12 months, MACE occurred in 11 (4.1%) of patients randomized to leuprolide and 15 (5.5%) of those randomized to degarelix. The greater hazard ratio for MACE in the degarelix group did not approach statistical significance (hazard ratio, 1.28; P = .53).
As a result, the question of the relative CV safety of these drugs “remains unresolved,” according to Dr. Lopes, professor of medicine at Duke University Medical Center, Durham, N.C.
This does not diminish the need to answer this question. In the addition to the fact that cancer is a malignancy primarily of advancing age when CV disease is prevalent – the mean age in this study was 73 years and 44% were over age 75 – it is often an indolent disease with long periods of survival, according to Dr. Lopes. About half of prostate cancer patients have concomitant CV disease, and about half will receive ADT at some point in their treatment.
In patients receiving ADT, leuprolide is far more commonly used than GnRH antagonists, which are offered in only about 4% of patients, according to data cited by Dr. Lopes. The underlying hypothesis of this study was that leuprolide is associated with greater CV risk, which might have been relevant to a risk-benefit calculation, if the hypothesis had been confirmed.