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 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.
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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."
SOURCE: http://bit.ly/2xhTzjq Journal of the National Cancer
Institute, online September 17, 2018.
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