The best way to identify people at high risk of cancer is by testing the family member who is most likely to carry a high-risk gene mutation
Cancer patients’ close relatives might be willing to get tests to see if they share genetic mutations that put them at risk for tumors, too, if testing were accessible and affordable, a U.S. experiment suggests.
Researchers asked 741 people with one of 30 cancer-associated mutations and 360 of their “first degree” relatives - a parent, sibling or child - to invite other close relatives to get their genes sequenced for about $50 - about one tenth of the standard cost.
Altogether, these individuals invited 2,280 first-degree relatives to get the genetic tests.
Over the first year of the discount testing program, 48 percent of the invited relatives agreed to testing. About 48 percent of these first-degree relatives tested positive for the same genetic mutation linked to cancer in their family member, and about five percent had a different variant also associated with tumors, the study found.
Then, 12 percent of these relatives who tested positive kept the “cascade” testing going by inviting additional family members to get tests.
“Cascade genetic testing - where relatives of people who carry a gene mutation are tested to find out if they also carry it - is one of the highest-yield ways to identify carriers and ultimately reduce their risks,” said lead study author Jennifer Caswell-Jin of Stanford University School of Medicine in Palo Alto, California.
Typically, only about one-third of relatives get tested, Caswell-Jin said by email. The current experiment set out to improve this by making the process easier and cheaper. People with cancer risk mutations could initiate testing online and then let laboratories contact relatives directly.
“The best way to identify people at high risk of cancer - which is the first step in reducing their cancer risks - is to start by testing the family member who is most likely to carry a high-risk gene mutation (for example, someone diagnosed with cancer at a young age, or with multiple cancers),” Caswell-Jin said.
“Our study explores an approach toward optimizing the process of testing other relatives in the family once one person has tested positive for a cancer risk mutation,” Caswell-Jin said.
Although not everyone with a cancer-associated mutation will go on to develop the disease, the knowledge that one is a carrier can help people and their doctors make informed health care decisions while they are still healthy, researchers note in the Journal of the National Cancer Institute.
For example, women with BRCA1 or BRCA2 mutations, who have a vastly increased risk of developing breast or ovarian cancers, may choose to undergo mastectomies or have their ovaries removed even without a diagnosis of cancer. Other types of mutations, such as those that increase one’s risk of colon cancer, may indicate the need for increased or more frequent screening.
One limitation of the study is that researchers only followed people for a year, and it’s unclear how many relatives who got tested might go on to develop cancer.
This type of testing often isn’t covered by insurance, and can cost hundreds of dollars.
“A major question is how results inform health-related decisions, and people need clinicians to help navigate the increasing complexity of this landscape,” said Dr. Steven Katz, a health policy researcher at the University of Michigan in Ann Arbor who wasn’t involved in the study.
“The direct harm to patients and relatives is that inaccurate test results could lead to undo worry or unwarranted procedures,” Katz said by email. “But emerging evidence suggests that this has not been the case so far.”
Tests may have less risk when genetic counselors are able to help with the decision to get tested and to put any positive or negative results in the right context for patients, said Dr. Lisa Newman, chief of breast surgery at Weill Cornell Medicine/New York Presbyterian Hospital Network in New York City.
“Those relatives that undergo genetic testing and are found to also carry the mutation might opt to pursue prevention strategies to reduce their cancer risk, or they might adopt enhanced cancer screening practices for early detection of disease,” Newman, who wasn’t involved in the study, said by email. “However, they will not have any of these choices if they are not aware of the familial/hereditary cancer risk.”