MUNICH — Hormone therapies that produced androgen deficiency in men were associated with significant prolongation of the QT interval in three different prostate-cancer studies.
“These findings should be considered when assessing the risk-to-benefit ratio of hormone therapy [in men], especially in patients with a baseline QT interval of more than 450 msec and in patients who are treated with class IA or class III anti-arrhythmic drugs,” Craig M. Pratt, M.D., said in a poster at the annual congress of the European Society of Cardiology. QT interval prolongation is associated with an increased risk of life-threatening arrhythmia and torsades de pointes ventricular tachycardia.
The data are consistent with testosterone having an important role in cardiac repolarization and possibly having a cardioprotective effect, said Dr. Pratt, a professor of medicine at Baylor College of Medicine in Houston.
He and his associates reviewed the results from three phase III studies that assessed several drugs in men with prostate cancer. All the drugs induced androgen deficiency.
In the first study, 177 men were treated with abarelix or with goserelin plus bicalutamide. In the second study, abarelix was compared with leuprolide, and in the third study, abarelix was compared with leuprolide plus bicalutamide. The second and third studies involved a total of 295 men.
All of the regimens studied were effective at reducing plasma levels of testosterone to 35 ng/ml or less, and all of the regimens led to prolongation of the QT interval, said Dr. Pratt, who is also director of the coronary care unit at the Methodist Hospital in Houston.
The extent of prolongation ranged from an average of 9 msec, when leuprolide plus bicalutamide were used, to an average of 20 msec, with leuprolide alone.