Boston—When and whether to use androgen deprivation therapy (ADT) can be a tough decision in prostate cancer cases.

The treatment, which is prescribed in about 50% of men diagnosed with the malignancy, successfully slows tumor growth for many patients but also increases risk of cardiovascular disease and sudden death.

A new study published in the Journal of the Endocrine Society helps explain why suppressing testosterone production has those effects.

“We showed that ADT results in electrophysiological changes in the heart,” explained first author Thiago Gagliano-Jucá, MD, PhD, a research fellow in the Section on Men’s Health at Brigham and Women’s Hospital. “The time it takes for these cells to be able to contract again after each beat increased following ADT, and prolongation of this time is a known risk factor of ventricular arrhythmias. We are trying to piece together how ADT might be resulting in sudden deaths in some men.”

The study points out that testosterone has been shown to decrease the time necessary for cardiomyocytes to contract again after a previous contraction. Reduced testosterone levels as a result of ADT prolongs the QTc interval on the electrocardiogram.

Researchers sought to determine the difference in change in QTc duration from baseline on a 12-lead electrocardiogram at 6, 12, and 24 weeks after initiation of ADT in 33 men compared with electrocardiograms performed at the same intervals in the non-ADT group consisting of 38 men. Also evaluated were PR, QRS, and QT interval durations.

Results indicate that ADT was associated with prolongation of the QTc by 7.4 ms compared with the non-ADT group {95% confidence interval [CI] 0.08 to 14.7 ms; P =.048). While ADT was also associated with shortening of the QRS interval by 2.4 ms (95% CI -4.64 to -0.23; P =.031), study authors report, electrolytes did not change.

“Oncologists should monitor QTc interval in patients receiving ADT, especially those patients who are taking medications that also prolong QTc interval,” Gagliano-Jucá advised.