About Ovarian Cancer Prevention
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Key Points
- In the U.S., a woman's lifetime risk of developing ovarian
cancer is approximately 1.4%, or 1 out of 70 women.
- Women who have a family history of ovarian and/or breast
cancer, especially in first-degree relatives (mother, daughter,
sister), have a greater chance of developing ovarian cancer
than women without such a history.
- An alteration in the BRCA1 or the BRCA2
gene increases a woman's lifetime risk of developing ovarian
cancer to between 16% and 60%.
- Monitoring for ovarian cancer in women at high genetic
risk is recommended to begin between the ages of 25 and
35 (or 5-10 years before the earliest age at which ovarian
cancer has been diagnosed in the family).
- Current recommendations for ovarian cancer screening of
women at high genetic risk include: CA-125 blood test once
or twice a year and transvaginal ultrasound once or twice
a year
- There is no evidence that following current screening
recommendations results in detecting ovarian cancer at an
earlier stage.
- There is no evidence that screening improves the survival
of women who are found to have ovarian cancer.
- Risk-reducing surgery may result in an 85 to 95% reduction
in the risk of ovarian cancer in women who carry a BRCA
gene mutation.
- Certain medications may lower the risk of ovarian cancer.
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Genetic Risk
In the United States, a woman's lifetime risk of developing ovarian
cancer is approximately 1.4%, or 1 out of 70 women. Women who have
a family history of ovarian and/or breast cancer, especially in first-degree
relatives (mother, daughter, or sister), have a greater chance of
developing ovarian cancer than women who do not have close relatives
affected with breast and/or ovarian cancer.
BRCA Gene Mutations
Women are at increased genetic risk of ovarian cancer if they have
an alteration in certain genes
that have been linked with hereditary
breast and /or ovarian cancer. An alteration in the BRCA1
or the BRCA2
gene increases a woman's lifetime risk of developing ovarian cancer
to between 16% and 60%. This broad range of estimates is due to
differences in how the existing research studies have been done.
However, there is no doubt that the risk of ovarian cancer is much
greater in women who have a strong family history and/or a mutation
in a BRCA gene than in women from the general population.
In addition, the risk of ovarian cancer is clearly lower for women
with BRCA2 mutations than it is for those who have BRCA1
mutations.
Early Detection
Reducing the burden of cancer is important to women who are at
high genetic risk of ovarian cancer, and it is a major goal for
the health care providers who treat these women. Like many other
cancers, the survival rates for ovarian cancer are much higher when
it is detected early. As a result, screening for ovarian cancer
in high risk women is recommended to begin between the ages of 25
and 35 (or 5-10 years before the earliest age at which ovarian cancer
has been diagnosed in the family).
Current Recommendations
Current recommendations for ovarian cancer screening of women at
high genetic risk include:
It is important to understand that these recommendations are not
supported by any evidence that using this screening program actually
results in detecting ovarian cancer at an earlier-than-usual stage.
Even more importantly, there is no evidence that screening improves
the survival of women who are found to have ovarian cancer. Clearly,
there is an urgent need for a proven, effective ovarian cancer screening
strategy in women who are at increased genetic risk.
In addition to screening, there are also medical and surgical approaches
to reducing the risk of ovarian cancer in high-risk women:
Risk-reducing Surgery
Risk-reducing salpingo-oophorectomy
(RRSO) involves removal of the ovaries
and fallopian
tubes before there is evidence that cancer has developed.
It has been estimated that this procedure may result in an 85 to
95% reduction in the risk of ovarian cancer in women who carry a
BRCA gene mutation. There is some uncertainty regarding precisely
how much reduction in risk is achieved with surgery, in part due
to the occurrence of an ovarian cancer-like illness (called primary
peritoneal carcinoma) in some women who have had preventive surgery.
Nonetheless, it is generally recommended that high-risk women seriously
consider this procedure after they have completed their childbearing.
In addition, there is some evidence to suggest that the risk of
breast cancer is lower among women who have had their ovaries removed
for preventive purposes.
Surgical removal of the ovaries from a woman who is still regularly
having her periods results in loss of fertility and the premature
(earlier-than-usual) onset of menopause. This is accompanied by
the usual symptoms of menopause related to decreased levels of estrogen
in the body. The decision to postpone surgery in some women is based
upon their concerns regarding the long-term effects of premature
menopause, such as increased risks of osteoporosis
(thinning of the bones) and cardiovascular
disease (including heart attack and stroke). Early menopause
may also have a significant impact on a woman's quality of life.
These issues have not been carefully studied in women at increased
genetic risk of ovarian cancer. One of the main reasons that the
current study is being done is to collect information on these important
questions.
Furthermore, the risks and benefits of menopausal hormone therapy
(MHT) in women with a BRCA mutation who have undergone RRSO have
not been clearly defined. Currently, the decision regarding whether
or not to use hormone therapy after risk-reducing surgery is made
on an individual basis by each woman and her health care providers.
Tubal ligation ("tying the tubes") may also help to reduce
the risk of ovarian cancer without actually removing the ovaries.
This avoids immediate menopause, but does not reduce cancer risk
as much as RRSO does.
Medical Prevention
The use of oral contraceptives (birth control pills) has been shown
to reduce the risk of ovarian cancer by about 50% among women in
the general population, but information about the potential risks
and benefits of oral contraceptives among women with BRCA1
and BRCA2 gene mutations is limited. One study has shown
a decreased risk of ovarian cancer following the use of oral contraceptives
in high-risk women, while another has shown no evidence of
risk reduction. Therefore, there is currently no consensus among
health care providers involved in caring for high-risk women as
to whether oral contraceptives should or should not be used. In
addition, there is both a theoretical concern, and a limited amount
of data, to suggest that the risk of breast cancer may be increased
with oral contraceptive use in high-risk women.
Finally, there is a great deal of research currently underway,
aimed at identifying other medications which might be used to lower
the risk of ovarian cancer. The technical term for such treatments
is chemoprevention.
Various different medications are being evaluated to see if they
might be safe and effective in reducing the chances that high-risk
women will develop ovarian cancer. One such study, designated "GOG
0190," is currently enrolling women in a research evaluation
of a medication called fenretinide,
which is related to vitamin A. Other such studies may be found by
searching NCI's
PDQ database.
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