Seattle, WA—One of the concerns in prescribing supplemental testosterone for men with low levels has always been the possible link between increasing hormone levels and prostate cancer.

Now, a new study in PLOS ONE reports that testosterone supplementation does not appear to be linked to an increased risk of aggressive prostate cancer.

A study team led by researchers from the University of Washington and the Veterans Affairs Puget Sound Health Care System, both in Seattle, came to that conclusion after examining records of nearly 150,000 men over age 40 with low testosterone levels who had been treated with supplements. 

“This finding doesn’t change the guidelines for how we recommend testosterone therapy,” said lead author Thomas Walsh, MD, MS, an associate professor of urology at the University of Washington School of Medicine and clinician at VA Puget Sound. “Men should still have their testosterone diagnosed appropriately, with multiple readings, and be counseled about risks and benefits of treatment. But this large foundation of evidence allows us to look patients in the eye and say testosterone therapy does not appear to increase risk of prostate cancer over a moderate duration.”

Background information in the study notes that testosterone treatment of men with low testosterone is common and, although usually short-term, has raised concern regarding an increased risk of prostate cancer (CaP), leading to the investigation of the association between modest-duration testosterone treatment and incident aggressive CaP.

The retrospective inception cohort study focused on male veterans aged 40 to 89 years with a laboratory-defined low testosterone measurement from 2002 to 2011 and recent prostate-specific antigen (PSA) testing. Overall, 58,617 of the participants were treated with testosterone, and 313 aggressive CaPs were diagnosed—190 among untreated men (incidence rate [IR] 0.57 per 1,000 person-years, 95% CI 0.49–0.65) and 123 among treated men (IR 0.58 per 1,000 person-years; 95% CI 0.48–0.69).

After adjusting for age, race, and hospitalization during the year prior to cohort entry, geography, BMI, medical comorbidities, and repeated testosterone and PSA testing, researchers determined that testosterone treatment was not associated with incident aggressive CaP (HR 0.89; 95% CI 0.70–1.13) or any CaP (HR 0.90; 95% CI 0.81–1.01).

Furthermore, they observed no association between cumulative testosterone dose or formulation and CaP.

“We now know that the nonaggressive variations can simply be followed over time and may not lead to significant increases in morbidity or mortality. So, for the study, we thought it was more important to identify the high risk prostate cancer associated with very high PSA or known histologically to be prone to spread,” Walsh said, emphasizing that the focus was on development of aggressive prostate cancer.

The study benefited from the VA’s closed medical and pharmacy system, he added, pointing out that using an integrated healthcare system reduced the likelihood that patients in the study received relevant care outside of the system. In addition, patients’ data sets included full medical histories, enabling researchers to better control for other serious illnesses that affected the study population’s mortality.

Finally, Walsh pointed out, most recipients of testosterone therapy received IM injection, the typical delivery mechanism during the study span and also the most biologically available testosterone therapy. 

“Many previous studies of testosterone delivered in topical cream or patch have shown that men never achieve a biologically therapeutic level. In our study, most men received injections and had follow-up tests that proved that their testosterone levels actually rose with the therapy,” he explained.
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