People who use personal genome profiles to learn their genetic risk for certain cancers don't seem to do much with the results, a recent study suggests.
Although most cancer-gene testing is done within the healthcare system, a small but growing number of people are getting broader cancer-risk profiles on their own through direct-to-consumer companies like 23andMe and Pathway Genomics. Some previous studies suggest that these tests can help motivate people to make changes to improve their health, but other research has found the opposite or linked the tests to wasteful and invasive procedures.
For the current study, researchers analyzed survey data from 762 customers who got personal genome profiles and received results detailing their probable risk for certain cancers including tumors of the colon, rectum, prostate and breast.
Six months after getting test results, the study found that people who were told they had an elevated risk of tumors were no more likely than those with average or below average risk to have changed their diet, started exercising or to have sought cancer screenings.
"Getting personal genomic tests outside of the traditional medical setting may make it more difficult for individuals to fully contextualize the testing results," said lead study author Dr. Stacy Gray, a researcher at City of Hope National Medical Center in Duarte, California.
The results from this group of people who were highly motivated to seek out testing on their own may not reflect the potential for personalized genomic tests to influence behavior changes in a wider population of patients, Gray added by email.
But, bottom line, lifestyle modifications like eating better and exercising more are tough to start and even harder to sustain, Gray said.
To get a sense of how personal genomic profiling might influence behaviors, researchers excluded people with any prior cancer diagnosis or previous experience with genetic testing.
Survey respondents were 42 years old on average, predominantly white and affluent with at least a college education.
Almost all of the women in the survey cited concerns about breast cancer risk as a main reason for getting tests, while the majority of men were worried about prostate tumors. Across both sexes, 88 percent of participants were interested in their colorectal cancer risk.
None of the participants were found to have the type of high-risk mutations that increase cancer risk significantly and with high certainty - and are typically the targets of medical genetic testing.
Instead, the profiles focused on gene variants implicated in slightly raising risk for certain cancers to calculate an overall risk profile for each of the three cancer types.
Six months after receiving test results, 31 percent of participants had made changes to their diets, 26 percent altered exercise habits, 6 percent changed advanced care plans and 21 percent shifted their use of vitamins and supplements, researchers report in the Journal of Clinical Oncology.
For the most part, people with elevated cancer genetic risk scores were not significantly more likely to make these changes than participants who received average or reduced risk estimates. Men with a higher risk of prostate tumors were an exception, because they were more likely to change their use of vitamins and supplements than men without an elevated risk.
The results mirror findings from earlier studies on genetic variants that increase the carcinogenic effects of smoking, said Dr. Mary Daly, a genetics researcher at Fox Chase Cancer Center in Philadelphia who wasn't involved in the study.
"Smokers who receive test results that indicate that they are at increased risk for lung cancer do not usually stop smoking," Daly said by email. "It may be that the risks associated with these tests are not high enough to result in any behavior changes, or it may be that people are skeptical about the results."
People may also see interventions like diet and exercise as too difficult, said Dr. Jennifer Litton of the University of Texas MD Anderson Cancer Center.
"Personalized genomic tests will not hold the expected medical crystal ball, nor will they tell you don’t need to consider the importance of recommended diet and exercise," Litton, who wasn't involved in the study, said by email.