Researchers at NYU Langone Medical Center, looking into the controversial association between testosterone replacement therapy (TRT) and prostate cancer risk, found that TRT had no impact on cancer risk but did help to maintain normal testosterone levels — and possibly protect against aggressive cancer — in healthy men with age-related low testosterone. The study, “Testosterone Therapy and Prostate Cancer Risk,” was presented at the recent 2016 American Urological Association annual meeting.

Concerns with testosterone replacement therapy and cancer risk are due, in part, to the fact that standard therapy for prostate cancer includes drugs that reduce testosterone levels in an effort to decrease tumor growth. But testosterone levels naturally drop with age, and with men living longer the use of testosterone replacement therapy is climbing, even though its effects are still largely unknown. Recent analyses have reported no increased prostate cancer risk in men on TRT, but these studies have had significant limitations, such as small sample size.

To determine if an association exists between TRT and cancer, researchers investigated data from 38,570 men with prostate cancer, diagnosed from 2009 to 2012, recovered from the National Prostate Cancer Register (NPCR), and compared them with 192,838 age-matched controls. Among this sample, 284 men had TRT prescriptions before being diagnosed with prostate cancer, while 1,378 in the cancer-free control group also had undergone TRT therapy. The analysis found no significant association between any TRT use and overall prostate cancer risk. However, researchers found a higher incidence of low-risk prostate cancers in men shortly after the start of TRT, possibly a result of more doctor visits and biopsies. Importantly, the team found a lower risk for aggressive disease among men on long-term TRT, over a year. The risk did not vary with the administration method used.

“Based on our findings, physicians should still be watching for prostate cancer risk factors — such as being over the age of 40, having African-American ancestry, or having a family history of the disease — in men taking testosterone therapy, but should not hesitate to prescribe it to appropriate patients for fear of increasing prostate cancer risk,” Stacy Loeb, MD, MSc, the study’s lead investigator and a Langone urologist, said in a news release. “Overall, our study suggests that what is best for men’s health is to keep testosterone levels balanced and within a normal range.”

Future research plans include investigating why low testosterone levels might trigger aggressive prostate cancer, and why maintaining normal levels seems to protect against it.