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Risk of Breast and Ovarian Cancer in Women With Strong Family Histories

Risk of Breast and Ovarian Cancer in Women With Strong Family Histories

ABSTRACT: Assessing the risk of breast and ovarian cancer starts with obtaining a complete and accurate family history. This can reveal evidence of inherited cancer risk. The highest risk of cancer is associated with germ-line abnormalities in several genes, including BRCA1, BRCA2, and TP53. Moderate-risk genes associated with syndromes that are inherited in an autosomal dominant pattern (such as Cowden’s disease, hereditary nonpolyposis colorectal cancer, Muir-Torre syndrome, and Peutz-Jeghers syndrome) exhibit lower penetrance and thus less risk of breast and/or ovarian cancer. Low-risk genes likely require significant environmental exposure, and although they are associated with the lowest risk of cancer, they account for more cancer than high- and moderate-risk genes. Lifetime risks for breast or ovarian cancer can be estimated. The Gail and Claus models, the more widely utilized models for calculation of lifetime breast cancer risk, are discussed. Models are also available for determining the likelihood of finding a BRCA1/2 mutation (the BRCAPRO and Myriad models). Appropriate candidates for testing include affected individuals who are most likely to have a hereditary form of cancer. Testing should proceed only after a thorough discussion of the risks, benefits, and limitations of testing. Risk-reducing options are available to women with a strong family history of breast and ovarian cancer. These options include high-risk screening, chemoprevention, and prophylactic surgery. [ONCOLOGY 15(7):889-913, 2001]


Approximately 30% of individuals with breast cancer have
some family history of cancer (generally breast and/or ovarian cancer).[1,2]
However, the majority of women who present with a family history of cancer will
not have a history that is suggestive of an autosomal dominantly inherited
disorder (cancer in multiple generations). It is estimated that only 5% to 10%
of breast and ovarian cancers are associated with a strong family history of
cancer and are, therefore, likely to be attributed to inheritance of a mutation
in a known cancer-causing gene.[3] Current information suggests that these genes
may be grouped into high-, moderate-, and low-risk genes.[4] Genes that confer
the greatest lifetime cancer risk can be thought of as high-risk genes.

In this article, we will focus on BRCA1, BRCA2, and TP53 (aka
p53) as high-risk genes.[3] Moderate-risk genes are inherited in an autosomal
dominant fashion with lower penetrance and therefore less cancer risk. Low-risk
genes can be associated with the smallest cancer risk. These genes and their
risk for cancer are less well understood, and the associated cancer risks are
controversial. Likely, cancer attributable to low-risk genes develops later in
life and is linked to significant environmental exposure.[5,6]

The commercial availability of genetic testing for cancer risk
introduces a new dimension in the assessment of breast and ovarian cancer risk.
Genetic testing for cancer risk is a complex process. Appropriate individuals
for testing should have the highest likelihood, within a family, of carrying a
cancer-causing gene mutation. Before undergoing genetic testing, individuals
must understand the risks, benefits, and limitations of genetic testing. This
includes understanding the psychological and ethical issues that surround
genetic testing.

The first steps in this process are gathering an accurate family
history and recognizing the features of hereditary breast and ovarian cancer. It
is also important to understand the options that are available for individuals
who are at high risk of cancer (those with a family history or found to be gene
mutation carriers).

High-risk cancer screening is available; however, these
screening recommendations are based on expert opinions and are largely unproven.
Options for cancer prevention include prophylactic surgery (oophorectomies,
mastectomy) and chemoprevention. The ability to counsel and provide an accurate
assessment of risk and appropriate screening recommendations for these
individuals is critical for the provider. We present guidelines for risk
assessment in individuals with a family history of breast and ovarian cancer and
review the management issues involved in caring for this group of women.

Gathering the History

Even in this era of microchip technology, an accurate family
history continues to be the most informative tool for assessing cancer risk.
Despite its importance in assessing risk, obtaining a family history is rapidly
becoming a lost skill. Significant deficits exist in the documentation of family
history in the primary care setting. This may stem from a diminution of the time
that is available for physician and patient interactions, as well as a lack of
emphasis during physician training. In one cross-sectional study, a family
history was obtained in only 50% of new patient visits and was updated in 22% of
established patient visits.[7]

The first step in obtaining an accurate cancer family history
involves gathering information to generate a pedigree that spans at least three
generations. The history should include all types of cancer in both the paternal
and maternal lineage, since breast and ovarian cancer risks can be transmitted
through the father. For each affected relative, it is important to try to
ascertain the site of the primary tumor, laterality of disease, age at
diagnosis, treatment, and age at death. Eliciting information about unaffected
family members is key to interpreting the family history and should include
cause of and age at death. If the total number of female relatives is small,
significant expression of an inherited gene may not be apparent. Gathering
information about the presence of other chronic diseases in the family, such as
osteoporosis and coronary artery disease, is important since this information
may influence management recommendations (eg, recommendations for hormone
replacement therapy).

Studies have shown that family history information that
identifies breast or colon cancer as a primary cancer site in first-degree
relatives may be accurate in 89% to 91% of cases.[8] However, the accuracy rate
for such information decreases in the case of second- and third-degree
relatives. Often, the diagnosis of premalignant conditions may be confused with
cancer, and sites of recurrence can be misidentified as second primary tumors.
Hence, procuring pathology reports or medical records to verify a family history
of cancer is strongly recommended. Ascertaining ancestry is an integral
component of the process. The existence of specific mutations (eg, BRCA1/BRCA2)
in certain populations makes ethnicity-based testing an important option to

Current advances in technology may incorporate new tools such as
computer programs to record genetic information,[9] but physicians will continue
to play an important role in the interpretation of this information and the
definition of risk. Future developments in genetic research will only serve to
increase the importance of an accurate family history. All physicians should
develop methods to capture family history at the time of an initial patient
visit and then periodically update this information.

Features of Hereditary Breast and Ovarian Cancer

Certain features of an individual’s personal or family history
may lead the clinician to suspect an inherited predisposition to breast and/or
ovarian cancer. A personal history of early breast cancer (onset at age < 50
years) or bilateral breast cancer may be a clue to a genetic predisposition.
Additionally, breast and ovarian cancer in the same individual may herald the
presence of hereditary malignancies. As we will discuss later, a history of
ovarian cancer or early breast cancer plus Ashkenazi Jewish ancestry carries a
significant risk of an inherited form of the diseases.

Inherited factors may play a role when the above personal
history coexists with early-onset breast cancer, bilateral breast cancer, male
breast cancer, or ovarian cancer in more than one generation. The presence of
other cancers in the family, such as cancers occurring at early ages (eg, colon
cancer at age < 50 years) or cancers without the usual risk factors (such as
lung cancer in a nonsmoker) may be clues to an inherited form of cancer. See
Table 1
for a list of other cancers that can be associated with hereditary
breast or ovarian cancer.

Families vary in size, and it is important to take into account
the number of individuals within a family, as well as the number of women at
risk. For example, a small family with few women over age 40 diagnosed with one
early breast cancer and ovarian cancer can be significant, whereas a very large
family with several women over age 60 affected with breast cancer may be less
likely to carry a genetic alteration in BRCA1/2.

Breast and ovarian cancer are features of several hereditary
syndromes. Families with clear autosomal dominant patterns of inheritance are in
the minority (5% to 10% of all individuals with either breast or ovarian
cancer).[3] More than 70% percent of such families will be found to carry
mutations in BRCA1 or BRCA2.[3] Individuals with BRCA mutations have high
lifetime cancer risks and will be discussed below as high-risk genes. Other
syndromes, such as Cowden’s disease, hereditary nonpolyposis colorectal cancer
(HNPCC), Muir-Torre syndrome, and Peutz-Jeghers syndrome also display autosomal
dominant patterns of inheritance. However, these carry a lower penetrance and,
therefore, a lesser lifetime risk of cancer. These syndromes have a moderate
lifetime cancer risk, and the genes associated with the syndromes have often
been termed moderate-risk genes.

Low-risk genes carry the lowest risk of cancer (relative risks
of 2.0 to 7.0) but are likely to be more prevalent than either high- or
moderate-risk genes. Therefore, they contribute more to the overall development
of cancer. To date, low-risk genes have not been associated with ovarian cancer,
and consequently, only low-risk genes associated with the risk of breast cancer
will be discussed in this article. See Table 2 for a list of high-, moderate-,
and low-risk genes, their associated syndromes, and lifetime risk of breast
and/or ovarian cancer.


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