Tumor tests, genetic risk analyses and other products or services sold online as personalized cancer medicine are often not backed by evidence, according to a new U.S. study.

Researchers say the websites touting products or advice also tend to promote the benefits of their services far more often than they note the limitations.

“I think that’s one of the challenges . . . it’s hard to know which sites are ones that are marketing tests that are really helpful, and which sites are marketing tests or services that aren’t helpful,” said Dr. Stacy W. Gray, a medical oncologist at Dana-Farber Cancer Institute in Boston who led the study. “It’s hard to know which are which.”

Gray, who is also an assistant professor of medicine at Harvard Medical School, said she and a coauthor had noticed that many of their patients asked questions about information they found on cancer care web sites.

“Knowing this is a fairly common thing, we wanted to better understand the Internet marketing landscape to see what patients might encounter online,” Gray said. “Studies over the last few years have shown in other contexts, not cancer, exaggerated claims that don’t match scientific evidence, so we wanted to evaluate what kinds of things are being marketed in cancer.”

So-called personal cancer medicine on the Internet includes analysis of tumor tissues, help interpreting tumor data or advice on the best treatments for an individual’s tumor, as well as testing for cancer risk.

Gray and her colleagues note in JNCI Journal of the National Cancer Institute that tests for inherited risk for developing certain cancers, or those that examine cancer cells have the potential to significantly improve cancer treatment. But because most cancer tests are not regulated by the Food and Drug Administration, some of the products being advertised don’t have proven benefits.

The researchers screened 4,910 websites, using search terms like personalized cancer medicine, individualized cancer treatment or targeted cancer care on Google, Yahoo and Bing, as well as gathering sites from scientific literature and conferences. They focused on the top 55 websites that matched their criteria for the study.

Most of the websites researchers found were commercially sponsored (56 percent), while others were promoted by academic institutions (20 percent), private institutions (15 percent) and individual doctors (2 percent).

Some of the commercial sites offered guidance about discussing their products with doctors, while a small percentage also included a directory of doctors who might provide their tests or services.

An expert panel helped determine whether the advertised tests had enough evidence to back-up claims of helping to treat cancer. For example, if large randomized controlled trials or large analyses of such trials found the tests effective, the panel considered the information trustworthy.

The panel found that a minority of websites (28 percent) sold tests they would endorse.

Half of the commercial websites included test prices, which ranged from $99 to $13,000. And while 85 percent of the websites described benefits of their products, only 27 percent specified potential limitations.

“The take home message for patients and doctors is that they need to be careful and critically evaluate what they see online,” Gray told Reuters Health. “If patients encounter things online they’re curious about, they should talk to their providers about whether those tests are helpful.”

Dr. Ben Park, an oncologist at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center in Baltimore said the study uncovered important information for patients and doctors.

“This study goes a long way into letting patients and physicians know that much of what is sold had not been truly validated,” said Park. “I think many in our business are aware of the over promise of these tests and the advertisements that accompany them.”

But Park noted that measuring the quality of the web sites was difficult because they were so different from one another.

“It’s also difficult to impossible to track outcome data since usually there is never follow-up after testing and/or the information could violate HIPAA (federal health) regulations,” he told Reuters Health in an email.

More testing is needed to gauge the effectiveness of personalized testing for cancer, Park said. “To take discovery research into clinical practice takes years to decades of further research and validation. This is no different than how a new drug gets put through multiple levels of clinical testing, yet for some reason, many such steps have been ‘skipped’ for personalized medicine testing.”