CV Safety Study of Cancer Therapy Attracts Attention

Ted Bosworth

August 31, 2021

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 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 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 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 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.

Cancer Drugs Can Increase CV Risk

Based on experimental data, "there is concern the leuprolide is involved in plaque destabilization," said Lopes, but he noted that ADTs in general are associated with adverse metabolic changes, including increases in LDL cholesterol, insulin resistance, and body fat, all of which could be relevant to CV risk.

It is the improving rates of survival for prostate cancer as well for other types of cancer that have increased attention to the potential for cancer drugs to increase CV risk, another major cause of early mortality. For these competing risks, objective data are needed to evaluate a relative risk-to-benefit ratio for treatment choices.

This dilemma led the ESC to recently establish its Council on Cardio-Oncology, and many centers around the world are also creating interdisciplinary groups to guide treatment choices for patients with both diseases.

"We need data to provide common ground on which to judge relative risks," de Boer said. He also praised the PRONOUNCE investigators for their efforts even if the data failed to answer the question posed.

The PRONOUNCE results were published online in Circulation at the time of Lopes's presentation.

The study received funding from Ferring Pharmaceuticals. Lopes reports financial relationships with Bristol-Myers Squibb, GlaxoSmithKline, Medtronic, Pfizer, and Sanofi. Suter reports financial relationships with Boehringer Ingelheim, GlaxoSmithKline, and Roche. De Boer reports financial relationships with AstraZeneca, Abbott, Bristol-Myers Squibb, Novartis, Novo Nordisk, and Roche.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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