By Nicholas Bakalar

New York Times News Service

Researchers searched YouTube for “prostate cancer screening” and “prostate cancer treatment.”

They scored the first 75 hits for each phrase, using validated scales to assess such measures as whether the video favored new technology, recommended unproven treatments, accurately described risks and benefits or showed commercial bias.

Outdated, biased or inaccurate videos were viewed more than 6.3 million times.

About 77 percent contained misinformation, 19 percent recommended unproven alternative medical treatments, and 27 percent had commercial bias favoring untested treatments. Three-quarters of videos described the benefits of various treatments.

Almost half failed to mention risks or side effects.

The study, in European Urology, found the greater the number of views, “likes” and “thumbs up” ratings a video received, the poorer the quality of the information tended to be.

The lead author, Dr. Stacy Loeb, an assistant professor of urology at New York University, said one video, viewed by more than 300,000 people, promoted Chinese herbal injections into the prostate, a treatment with no scientific validity.

“Don’t believe everything you see online,” she said.