CHICAGO (AP) — Hormone-blocking drugs for prostate cancer may increase men’s chances for developing dementia, a large study suggests, but researchers say the results aren’t conclusive enough to recommend avoiding a treatment that can improve survival.
Cancer patients who used the drugs faced about double the chances of being diagnosed with dementia over five years, compared with nonusers. The actual risk of dementia, though, was quite low for all the men.

The researchers analyzed 20 years of electronic health records for almost 9,300 prostate cancer patients treated at Stanford University’s health system. About 20 percent of the men were given hormone blockers, which lower levels of testosterone and other hormones that can fuel cancer growth.

After five years of follow-up, about 8 percent of men on hormone blockers were diagnosed with dementia versus almost 4 percent of nonusers.

The results were published Thursday in the journal JAMA Oncology. The researchers and others say rigorous studies are needed to prove whether the widely used treatment is risky.

About half of all prostate cancer patients in developed countries receive the treatment, including about 500,000 U.S. men currently on the drugs.

How the medicines might increase dementia risks is uncertain. One possible explanation is their effect on testosterone levels. That hormone can drive cancer cell growth, but low levels have also been linked with heart and blood vessel problems that can also contribute to dementia.

The treatment is often used for men who don’t receive surgery or radiation or whose cancer has spread to other parts of the body. It’s typically given in pills and injections for a few months up to a few years although some men with advanced disease stay on the treatment indefinitely, said Dr. Kevin Nead, the lead author and a cancer doctor at the University of Pennsylvania.

Some men who can’t tolerate the harsh treatment because of older age or other health problems are sometimes put on hormone blockers. Nead said the researchers took into account other ailments that may also increase risks for dementia. But he said some conditions may have been missed and he stressed that more research is needed.

Some but not all previous studies that also reviewed medical records have also suggested the treatment may increase risks for dementia. Men in the current study were part of a larger study that included University of Pennsylvania patients and that found an increased risk for Alzheimer’s disease, one type of dementia. That study, co-authored by Nead, was published last December in the Journal of Clinical Oncology.

Such studies typically use diagnosis and billing codes in medical records to gauge treatment risks or disease trends. Nead and colleagues used a newer computerized method that scans electronic records including doctors’ and nurses’ written notes, to find the same kind of information.

A JAMA Oncology editorial by Vanderbilt University physicians says the results suggest a link, not a cause.
“The authors rightly frame their conclusions as associations in need of further study,” Drs. Colin Walsh and Kevin Johnson said in the editorial.

By Lindsey Tanner, AP Medical Writer