By Jan Biles
THE CAPITAL-JOURNAL
WESTWOOD -- No one knows the exact causes of breast cancer or why
one woman develops breast cancer and another one doesn't. However,
research has shown women with certain risk factors are more likely
to develop the disease.
"We describe risks as average, high or hereditary," said Jennifer
Klemp, assistant professor at The University of Kansas and managing
director of KU Breast Cancer Survivorship Center at Westwood. "Most
women have average risk."
One out of seven women will develop breast cancer at some point
in her life, according to the American Cancer Society. The average
age of onset is 44.
Klemp said studies have identified the following risk factors for
breast cancer:
- Overweight or obesity after menopause. Klemp said the chance of
getting breast cancer or breast cancer recurring increases 30
percent to 50 percent in postmenopausal women who are overweight or
obese.
Before menopause, the ovaries produce most of a woman's estrogen,
with fat tissues producing a small amount, according to the American
Cancer Society. After menopause, most of a woman's estrogen comes
from fat tissue. The more fat tissue, the higher a woman's estrogen
levels. Estrogen stimulates cell proliferation, which increases the
risk of developing breast cancer.
Klemp said losing weight, increasing muscle mass and reducing
one's body fat index can help lower estrogen levels.
"It's one thing that is modifiable and people can do something
about," she said.
- Personal or family history. A woman who has breast cancer in
one breast has an increased risk of getting it in the other breast.
About 20 percent to 30 percent of women diagnosed with breast
cancer have a family member with the disease, according to the
American Cancer Society.
A woman's risk of getting breast cancer doubles if her mother,
sister or daughter had breast cancer, and increases five-fold if two
of those close relatives had cancer. The risk also is higher if the
family member was diagnosed before age 40.
- Reproductive and menstrual history. Klemp said a woman has a
greater chance of getting breast cancer if she had her first child
at an older age; had her first menstrual period before age 12; went
through menopause after age 55; never had children; had a pregnancy
that didn't reach full term; or took menopausal hormone therapy with
estrogen plus progestin after menopause.
- Abnormality on mammogram that required a biopsy. Certain types
of abnormal cell growth, such as atypical hyperplasia and lobular
carcinoma in situ, increase the risk of breast cancer.
- Breast density. Women with denser breast tissue, as seen on a
mammogram, have more glandular tissue and less fatty tissue. They
are four to five times more likely to get breast cancer, according
to Susan G. Komen for the Cure.
- Alcohol. Women who consume two to five drinks a day have about
1 1/2 times the risk of women who drink no alcohol, according to the
American Cancer Society.
Additional risk factors listed by the American Cancer Society
include:
- Age. Most cases of breast cancer occur in women 60 and older.
- Gene changes. About 5 percent to 10 percent of breast cancer
cases result from gene defects inherited from a parent. The most
common cause of hereditary breast cancer is an inherited mutation of
the BRCA 1 and BRCA 2 genes.
- Race and ethnicity. White women have a slightly higher risk of
breast cancer than African-American women, but African-American
women are more likely to die of the disease because they tend to
have more aggressive tumors. Asian, Hispanic and American Indian
women have a lower risk of developing and dying from breast cancer.
- Radiation therapy to the chest. A woman who has radiation
therapy to the chest before age 30 is at higher risk for breast
cancer.
- Diethylstilbestrol. Pregnant women were given DES from the
1940s to 1960s to prevent miscarriage. Those women and their
daughters have a slightly increased risk for breast cancer.
- Lack of physical activity. Being active can prevent weight gain
and obesity.
"(Women need to) exercise three to four times a week," Klemp
said. "The intensity factor is important. Walking won't do it. It
needs to be more than a stroll."
- Recent use of oral contraceptives.
Roy Jensen, director of The University of Kansas Cancer Center in
Kansas City, Kan., said there is "a lot of good news" in the areas
of breast cancer diagnosis and treatment.
Breast cancer is diagnosed at an earlier stage, he said, and the
five-year survival rate has improved, from 75 percent in 1975-80 to
an average of 90 percent today.
Jensen said surgeries to treat breast cancer aren't as
disfiguring, advancements have been made in radiation techniques,
and therapies are more targeted.
Klemp said two drugs that are used to prevent breast cancer are
available to women considered at high risk for the disease.
Tamoxifen blocks estrogen by binding to estrogen receptors, which
causes cancer cells that need estrogen to divide to stop growing and
die. Raloxifene, which is prescribed to postmenopausal women, also
stops breast cells from being affected by estrogen.
"Progress has been slow and steady," Jensen said, "but it doesn't
show any sign of abating."
Jan Biles can be reached at (785)295-1292 or
jan.biles@cjonline.com.
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