Sept. 23, 2009 (Berlin) -- The anti-hormone therapies used to treat prostate cancer can raise the risk of heart disease, but some drugs appear to be safer for the heart than others, researchers report.
The study, the largest to date to look at the issue, suggests that overall, anti-hormone therapies were associated with about a 25% increased risk of heart disease.
But in a more detailed analysis by type of hormone therapy, agents known as gonadotropin-releasing hormone agonists proved more risky than anti-androgen drugs, says Mieke Van Hemelrijck, a PhD candidate in cancer epidemiology at King's College in London.
The results were presented at a joint meeting of the European Cancer Organization and the European Society of Medical Oncology (ESMO).
Anti-Hormone Treatments for Prostate Cancer
Prostate tumors "grow in an environment of [the hormone] testosterone, so a common treatment is to block testosterone, either by interrupting its production or by making sure testosterone can't get into the prostate," she says.
That can be achieved in one of three ways. Some men undergo surgical removal of the testicles to eliminate the body's main source of testosterone production.
Others receive injections of gonadotropin-releasing hormone agonists. They actually block testosterone production by the testicles, so there is almost no circulating testosterone in the body, Van Hemelrijck says. Examples include Lupron, Viadur, Eligard, Zoladex, Trelstar, and Vantas.
Anti-androgen pills, on the other hand, block testosterone from attaching to prostate cells. "This means there is still testosterone in the body; it just can't get to the prostate," she says. These include Eulexin, Casodex, and Nilandron.
Measuring Risk of Prostate Cancer Treatments
The new study involved more than 30,000 men in Sweden with advanced prostate cancer who received anti-hormone treatments between 1997 and 2006. The researchers compared their rates of heart problems to those in the general Swedish population.
Most of the patients received one treatment, but 38% received both gonadotropin-releasing hormone agonists and anti-androgen pills. The men were followed for about three years.
Overall, anti-hormone therapies were associated with a 24% increased risk of heart attack, a 19% increased risk of irregular heartbeats known as arrhythmias, a 31% increased risk of ischemic heart disease, and a 26% increased risk of heart failure. The risks began to climb within a few months of starting hormone therapy.
Prostate cancer patients treated with anti-hormone therapies also had a 22% to 41% higher chance of dying of a heart attack or other type of heart disease, compared with the general population.
But further analysis showed that while all three forms of anti-hormone therapy were associated with an increased risk for heart disease, anti-androgens were associated with the lowest risk." Patients on gonadotropin-releasing hormone agonist therapy had the highest risk of these problems," Van Hemelrijck says.
For example, men given anti-androgen pills had a 15% increased chance of developing ischemic heart disease vs. a 33% increased risk in the men who received gonadotropin-releasing hormone agonists.
Since men given anti-androgens still have circulating testosterone in the body, the findings "support support the hypothesis that testosterone is protective for the heart," Van Hemelrijck says.
Risks vs. Benefits
While the study does not prove that anti-hormone drugs cause heart ills, "they show the importance of taking heart disease into account when considering anti-hormone therapy, especially since it is now being given to men with earlier-stage disease," she adds.
While increased, the risks are still low in absolute terms, says ESMO President Jose Baselga, MD, chairman of the medical oncology service at the Vall d'Hebron University Hospital in Barcelona, Spain.
For example, the researchers estimated that anti-hormone therapies cause an extra one heart problem per year for every 100 prostate cancer patients treated, he notes.
"Untreated, advanced prostate cancer is a lethal condition. For most men, the benefits of anti-hormone therapy ultimately outweigh the increased risk of heart problems," Baselga says.
That said, he and Van Hemelrijck agree that men at risk for heart disease should talk to their doctor and undergo a through heart health exam before starting anti-hormone treatment.