MONDAY, July 8, 2019 (HealthDay News) -- Soon after a man is diagnosed with prostate cancer, drugs that lower levels of testosterone are often offered as treatment, since testosterone fuels the cancer's growth.
But a major new study suggests that this approach might have an unwanted side effect: Higher odds for Alzheimer's disease and other dementias.
"Our results suggest that clinicians need to raise their awareness about potential long-term cognitive effects of hormone therapy and discuss these risks with their patients," said study author Ravishankar Jayadevappa.
He's a research associate professor of geriatrics at the University of Pennsylvania's Perelman School of Medicine in Philadelphia.
One expert said it does raise troubling questions.
"Most of us are becoming as afraid of getting Alzheimer's as we are of getting cancer," said Dr. Elizabeth Kavaler, a urology specialist at Lenox Hill Hospital in New York City. "When a study pits one debilitating condition against another, it instills fear in patients."
But the treatment -- called androgen-deprivation therapy -- remains the "gold standard" for many cases of prostate cancer, according to Kavaler. Therefore, the new data means "tough decision-making" for patients and their physicians, she said.
In the new study, Jayadevappa's group took a look back at U.S. National Cancer Institute data on over 154,000 prostate cancer patients who were diagnosed between 1996 and 2003. About 62,000 received hormone-depleting therapy within two years of their diagnosis, while about 92,000 did not.
In total, 13% of men who had received the therapy went on to develop Alzheimer's disease over eight years of follow-up, compared to 9% who hadn't gotten the treatment, the study found. According to the researchers, the lifetime prevalence of Alzheimer's disease in men generally is about 12%.
When the team looked at diagnoses of all forms of dementia, 22% of those who'd received the therapy received such a diagnosis, compared to 16% of those who hadn't undergone hormonal therapy.
Jayadevappa's team noted that earlier, smaller studies have found similar trends.
However, "to our knowledge, this is one of the largest studies to date examining this association, and it followed patients for an average of eight years after their prostate cancer diagnosis," he said in a university news release.
As the researchers noted, androgen-deprivation therapy is an effective means of slowing the progress of prostate cancers. However, it is now typically only used in cases of advanced disease, or cases where the chances of a tumor recurrence are high.
The approach also has other deleterious side effects, including impaired sexual function, and potential harm to bones and cardiovascular health.
The study also can only point to an association between hormonal treatment and raised odds for dementia, it cannot prove cause and effect. But Jayadevappa's team noted that they tried to account for other factors, such as age, the presence of other medical conditions and the severity of the prostate cancer.
Dr. Maria Torroella Carney is chief of geriatric and palliative medicine at Northwell Health in New Hyde Park, N.Y. Looking over the findings, she said they warrant further study, but it's not time for men who've gotten hormonal therapy to panic.
Carney stressed that the study couldn't prove cause and effect, and other factors might account for the higher risk of dementia.
Men receiving hormonal therapy tended to be "older, sicker and had more advanced prostate cancer," Carney noted, and sicker patients already have higher odds of dementia.
In addition, the study didn't reveal whether or not men who got the therapy lived longer than those who didn't. If they did live longer, their odds of dementia would also increase over time, Carney explained.
Study co-author Dr. Thomas Guzzo agreed that no one should make rash decisions on prostate cancer care based on this study alone.
"I think we need to look at these patients on an individual level," said Guzzo, who is chief of urology at the University of Pennsylvania. "Certainly, there are patients who need hormonal therapy and benefit from it greatly," he said in a university news release. "There are others where the evidence is less clear, and in these patients, we should consider the risk of hormonal therapy versus the benefit in treating their prostate cancer. This should be a shared decision-making process with the patient."
The study was published online July 3 in JAMA Network Open.
Learn more about treatment for prostate cancer from the American Cancer Society.