Even people who carry genetic changes that put
them at higher-than-average risk of breast cancer can lower that risk —
sometimes by a lot, researchers said Thursday.
They predict that close to 30 percent of breast
cancer cases among white women could be prevented if all the women did
just four things: avoided smoking, drank very little alcohol, kept a
healthy body weight and skipped hormone replacement therapy.
A nurse performs a mammogram. MYCHELE DANIAU / AFP - Getty Images file
"Overall, we estimated that up to 28.9 percent
of all breast cancers could be prevented if all white women in the U.S.
population were at the lowest risk from these four modifiable risk
factors," Nilanjan Chatterjee of the Johns Hopkins Bloomberg School of
Public Health and colleagues wrote in their report, published in the Journal of the American Medical Association's JAMA Oncology.
Chatterjee is quick to say the calculation is
not ready for the average person to use yet. But he says the findings
offer hope to people who may find out they have a "cancer gene" and feel
they are doomed. "Lifestyle plays such an important role even in the
context of genetic risk," he told NBC News. Related: Exercise Lowers These 13 Cancer Types
With DNA tests becoming more common, easy to get
done and coming down in price, more and more people will find out they
have a rare mutation that raises their cancer risk, Chatterjee said.
"There is so much in the news that everything is determined by genetic
risk," he said.
His finding shows there is something people can
do. And there's no risk to not smoking, keeping at a healthy weight,
limiting drinking or avoiding HRT.
"It doesn't hurt anybody but what happens sometimes is that people lack motivation," Chatterjee said.
The team studied the cases of more than 40,000
women taking part in breast cancer and other health studies. They looked
at 92 common mutations known to raise breast cancer risk. They left out
the two best-known breast cancer risk genes — BRCA1 and BRCA2 — because
they're so clearly defined and studied. Related: Half of Cancer Deaths Due to Bad Habits
Chatterjee said his team wanted to address the
thousands of women who don't have BRCA1 and BRCA2 mutations who find out
they have other mutations that may raise their breast cancer risk. And
he said these 92 common mutations, which women usually don't know about,
account for more cases of breast cancer than the BRCA genes do.
Future studies should add those in, he said, as well as other known breast cancer genes.
Eventually, the model might be used to help
women know if they need to start getting mammograms early if they're at
especially high risk, or if they can spread out their mammograms later
in life because they're at lower risk.
"Our analysis shows that use of a model based on
most known risk factors can change the recommendation for screening for
a substantial fraction of the population, compared with using only
age-based criteria," the team wrote.
They calculated that 16 percent of 40-year-old
women have the breast cancer risk of someone 10 years older and might
want to get mammograms earlier than recommended. And they said 32
percent of 50-year-old women have a lower-than-average risk for their
age. "These women benefit least from screening and may benefit from
additional counseling about risk of false-positive results," the team
wrote.
The American Cancer Society estimates that more
than 230,000 U.S. women will be diagnosed with breast cancer this year,
that 40,000 women will die from it and that one in eight women will be
diagnosed at some point in their lifetimes.
The team said they calculated risks for
different groups. "The absolute cumulative risk of a 30-year-old white
woman in the United States developing invasive breast cancer over the
next 50 years is 11.3 percent on average," they wrote. Related: New Breast Cancer Study Raises Questions
Three outside experts agree that it's too soon
to use the calculation in real life. "It remains premature— in our
opinion — to use this model to support such clinical decision-making,"
Dr. William Dupont, Dr. Jeffrey Blume and Dr. Jeffrey Smith of
Vanderbilt University wrote in an editorial.
But Chatterjee says there are ways to make the
risk calculation better and more accurate. These include adding known
risk factors such as education, breastfeeding, physical activity,
conditions such as having dense breasts, and hormone levels. It will
also be important to include non-white women in the calculation.
Currently, women are steered to the Gail Model to calculate breast cancer risk. It factors in age, family history of breast cancer, pregnancy history and race.
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