DISORDER/SETTING  

Question 1: What is the specific clinical disorder being studied?

The primary clinical disorder being studied in this report is breast cancer in women.  However, since this report focuses on testing for mutations in the genes BRCA1 (breast cancer gene 1) and BRCA2 (breast cancer gene 2) that predispose women to both breast and ovarian cancer, ovarian cancer will also be reviewed. 

Excluding non-melanoma skin cancers, breast cancer is the most common form of cancer among women in the United States.  The American Cancer Society estimates that in 2002 about 203,500 new cases of invasive breast cancer and 54,300 cases of in situ breast cancer will be diagnosed among women in the United States. (2002)   It is estimated that 39,400 women will die of breast cancer this year, ranking it second among cancer deaths in women, exceeded only by lung cancer.  Although not as common as breast cancer, ovarian cancer accounts for nearly 4 percent of all cancers among women (23,400 diagnosed cases) and is estimated by the American Cancer Society to cause 13,900 deaths in 2002.  Ovarian cancer has the highest mortality rate of all reproductive system cancers in women.  The public health impact of these two cancers in women is substantial.  In 1997, breast cancer ranked second only to lung and bronchus cancer in terms of person-years of life lost (809,000), a measure of total burden of a cancer on society. (Brown et al., 2001)   Ovarian cancer ranked ninth, with 232,000 person-years of life lost.  Both cancers ranked higher than lung, colon/rectum, and prostate cancer in terms of average years of life lost per person (breast 19.3, ovarian 17.2).  This is a measure of burden that gives more weight to cancers that tend to occur in people at relatively younger ages.  In terms of financial impact, a direct cost of treatment of 5.98 billion dollars was noted for breast cancer, based on 1996 Surveillance, Epidemiology, and End Results (SEER) Medicare linked data.  

According to a report from the National Cancer Institute, it is estimated that about 1 in 8 women in the United States will develop breast cancer, the greatest risk being for women who live longer. (Ries et al., 2002)   Although quite rare, breast cancer can occur in men, and is estimated to affect 1,500 men each year. (2002)   Most breast cancers occur postmenopausally in women over age 50, and the risk is especially high for women over age 60.  While it is uncommon for women under age 35 to be diagnosed with breast cancer, the course of the disease is more aggressive in that age group.  There is also an increased likelihood for an underlying genetic predisposition, but the data are less clear for women whose cancers occur under age 30 (Question 18). 

Numerous risk factors for breast cancer have been identified and include advancing age and family history, as well as other endocrine and environmental factors.  It has been estimated that 5 to 10 percent of breast cancer cases demonstrate an autosomal dominant pattern of inheritance.  The cancer susceptibility syndromes most associated with this pattern are hereditary breast and ovarian cancer due to BRCA1/2 mutations, Li-Fraumeni syndrome due to p53 mutations, and Cowden syndrome due to PTEN mutations.  Most known mutations that increase breast cancer risk also appear to increase risk of ovarian cancer and may also increase risk of other cancers.  For instance, mutations in BRCA1/2 are associated with a 36 to 87 percent lifetime risk for breast cancer, and a 9 to 66 percent lifetime risk of ovarian cancer.  Most of the increased risk of breast cancer over background in women with BRCA1/2 mutations occurs premenopausally. (2000; Antoniou et al., 2000; Antoniou et al., 2002; Brose et al., 2002; Easton et al., 1995; Fodor et al., 1998; Ford et al., 1994; Ford et al., 1998; Hopper et al., 1999; Moslehi et al., 2000; Risch et al., 2001; Satagopan et al., 2001; Schubert et al., 1997; Struewing et al., 1997; Thorlacius et al., 1998; Warner et al., 1999)

DISORDER/SETTING 

Question 2: What are the clinical findings defining this disorder?

Breast cancer
Breast cancer is defined as the presence of a malignant tumor(s) within the breast tissue.  These tumors are made up of groups of abnormal cells that divide without control or order, and can invade and damage other tissues and organs.  These features distinguish them from a benign tumor.  A definitive diagnosis of breast cancer can be made only after biopsy and pathological examination. 

The earliest physical signs of breast cancer typically include:

§         a palpable lump

§         thickening, swelling, distortion, or tenderness

§         skin irritation or dimpling

§         nipple pain, ulceration, or retraction.  

The malignancy is initially localized.  It then spreads to surrounding tissues and lymph nodes.  The natural history of breast cancer can be altered by early detection methods, such as mammography, and by early treatment, which provides the best hope for total eradication.  A standard histological classification of the various tumor types has been provided by the World Health Organization.  Breast cancers can be further graded (1, 2, or 3 based on level of differentiation of the cells on histologic characterization) and staged based on tumor size, involvement of lymph nodes, and presence of metastases.  This grading allows standardization for comparison of results of various modes of therapy.  Additional information from results of testing regarding the presence of estrogen and progesterone receptors, cancer cell ploidy and proliferation rate, and testing for the HER2/neu protein also aids in determining appropriate treatment. 

Epidemiologic data suggest that genetic, endocrine, and environmental factors may be involved in the initiation and/or the promotion of breast cancer growth.  It is well known that the risk of breast cancer increases with age.  Important other risk factors include early age at onset of menarche, late onset of menopause, first full-term pregnancy after age 30, a history of premenopausal breast cancer in a mother or sister, and a personal history of breast cancer or benign proliferative breast disease. 

Ovarian cancer
Unlike breast cancer, signs and symptoms of ovarian cancer often appear late and are non-specific (e.g., general abdominal discomfort and/or pain, loss of appetite, nausea, diarrhea, constipation, frequent urination, weight gain or loss, and occasionally vaginal bleeding).  Ovarian cancer can be of three types; epithelial carcinoma, germ cell tumors, or stromal tumors, depending on the specific tissue involved.  Epithelial cancer is the most common type.  Like breast cancer, the risk for ovarian cancer increases with age and peaks when women are in their late 70s.  Most other risk factors for breast cancer are also risk factors for ovarian cancer.  Mutations in the BRCA1/2 genes increase the risk of epithelial ovarian cancer.  Increased risk of germ cell and stromal tumors has not been demonstrated.  

Further Information
Further information about genetic and environmental factors influencing breast and ovarian cancer can be found in Question 25.  More information about the natural history of breast cancer and ovarian cancer can be found in Question 26.

DISORDER/SETTING 

The decision to offer and perform BRCA1/2 mutation testing is based on the presence of personal and/or family risk factors that determine the probability of finding a deleterious mutation (Question 5).  The American College of Medical Genetics (ACMG) published guidelines in 1999, with a recommended protocol for Breast/Ovarian Cancer Genetic Susceptibility Assessment to aid health care providers. (1999)   These guidelines stress the importance of all the components of the recommended protocol, including family history risk assessment, pre-test education and post-test counseling.  The clinician may choose to manage all aspects, or may work in concert with an expert in cancer genetic counseling and risk assessment.  The guidelines state that risk assessment should begin with estimating the likelihood of developing breast or ovarian cancer through a complete personal and three generation family history, including all types of cancer and approximate age at diagnosis for each affected individual.  According to ACMG, the likelihood of having a mutation in a known cancer susceptibility gene (e.g. BRCA1/2) should be assessed on the basis of number of family members with breast or ovarian cancer, the closeness of the relationship to the patient, the ages at diagnosis, and whether or not an individual is a member of an ethnic group at higher risk for specific mutations. 

The ACMG guidelines propose that there is sufficiently increased risk to warrant offering testing for a mutation in the BRCA1/2 gene if:

·        There are three or more affected first or second degree relatives on the same side of the family, regardless of age of diagnosis, or

·        There are fewer than three affected relatives, but

§         the patient was diagnosed at age 45 or younger, or

§         a family member is known to carry a detectable mutation, or

§         there are one or more cases of ovarian cancer and at least one relative on the same side of the family with breast cancer (at any age), or

§         there are multiple primary or bilateral breast cancers in the patient or one family member, or

§         there is breast cancer in a male relative, or

§         the patient is at increased risk for specific mutation(s) due to ethnic background (e.g. Ashkenazi Jewish), and has one or more relatives with breast or ovarian cancer 

In the absence of these personal and family risk factors, the protocol does not recommend further testing.  Before BRCA1/2 mutation testing is performed, the ACMG guidelines require that women at increased risk undergo a process of pre-test education regarding risks, benefits, alternatives and psychological/social impact of testing, so that they can make an informed choice about whether or not to proceed.   

The American Society of Clinical Oncology (ASCO) published a revised statement on Genetic Testing for Cancer Susceptibility. (2003)    ASCO recommends that cancer predisposition testing be offered only when:

1)      the individual has personal or family history features suggestive of a genetic cancer susceptibility condition,

2)      the test can be adequately interpreted, and

3)      the results will aid in the diagnosis or influence the medical or surgical management of the patient or family members at hereditary risk of cancer.  

ACMG recognizes the importance of testing an affected member of the family first to identify the familial mutation.  In the absence of knowing the mutation associated with cancer, a negative test in an unaffected family member is uninformative.  Table 1-1 contains a comparison of the ASCO and ACMG guidelines with other national guidelines.  In general, there is a high degree of consistence between the guidelines. 

For the purposes of this report, the Ashkenazi Jewish population is not being considered separately.  In addition, the focus is on screening women in the general population without a personal history of breast or ovarian cancer, using family history as the first screening test.

DISORDER/SETTING 

Question 4.  What DNA test(s) are associated with this disorder?

Background
Several genes have been identified in which germline mutations are associated with an increased risk for breast and ovarian cancer. 

·        BRCA1 is localized on chromosome 17q12-21, spans a genomic region of almost 100 kilobases (kb) in length and contains 24 exons.  The full-length messenger RNA (mRNA) is 7.8 kb, encoding a protein of 1,863 amino acids.  More than 1,200 mutations and sequence variations have been detected, and not all mutations have yet been discovered. 

·        BRCA2 has been isolated on chromosome 13q12-13 and is composed of 27 exons distributed over roughly 70 kb of genomic DNA, encoding a protein of 3,418 amino acids.  Approximately 1,400 mutations have been reported for BRCA2.   

Microinsertions and point mutations are equally common in the BRCA1 gene, whereas microdeletions predominate in BRCA2.  Large recurrent rearrangements, ranging from 0.5 to 23.8 kb and spanning the entire BRCA1/2 genes, have recently been discovered. (Montagna et al., 1999; Nordling et al., 1998; Payne et al., 2000; Petrij-Bosch et al., 1997; Puget et al., 1999; Puget et al., 1997; Rohlfs et al., 2000; Swensen et al., 1997; Unger et al., 2000)   These rearrangements are not detectable by usual polymerase chain reaction (PCR)-based laboratory methods (including sequencing and scanning).  These rearrangements represent an estimated 10 to 15 percent of all mutations in the general population (Puget et al., 1999; Unger et al., 2000) and up to 36 percent in the Dutch population. (Petrij-Bosch et al., 1997) .  The influence of these rearrangements on clinical validity is discussed later (Question 18).  Evidence suggests that the BRCA1/2 genes are tumor-suppressive via regulation of cellular proliferation and DNA replication and repair. (Holt et al., 1996; Patel et al., 1998; Scully et al., 1997; Scully and Livingston, 2000; Sharan et al., 1997; Zhong et al., 1999) 

Forty-eight different deleterious BRCA1 mutations were found in 102 out of 798 (12.8%) unrelated high-risk women. (Shattuck-Eidens et al., 1997)   Overall, 27/102 (27%) of the mutations were 187delAG, 17 percent were 5385insC (commonly referred to as 185delAG and 5382insC, respectively), and the remaining mutations were found at less than 4 percent frequency.  Founder mutations have been described for different ethnic populations: Ashkenazi Jewish women are ten times more likely than non-Jewish Caucasian women to harbor a 185delAG or 5382insC BRCA1 mutation, or a 617delT BRCA2 mutation.  (Couch and Weber, 1996; Oddoux et al., 1996; Struewing et al., 1997; Tonin et al., 1995)   An Ashkenazi Jewish woman's odds of a deleterious BRCA1 mutation are more than four fold greater than those for a non-Jewish Caucasian woman.  Other BRCA1/2 founder mutations have been identified in the Netherlands, Belgium, Norway, France, Sweden, Denmark, Scotland, Eastern Europe, Iceland, and in French-Canada. (Bergthorsson et al., 2001; Johannesdottir et al., 1996; Martin and Weber, 2000; Petrij-Bosch et al., 1997; Thorlacius et al., 1996; Tonin et al., 1998)  

Laboratory testing
Current recommendations call for screened women with a greater than 10 percent likelihood of having a detectable mutation to undergo testing (Questions 5 and 6).  Because of patent restrictions, the only facility legally authorized to perform sequencing for BRCA1/2 mutations for use in patient care is Myriad Genetic Laboratories (Salt Lake City, UT).  This laboratory provides several types of BRCA1/2 analyses.  The following list prices were in effect in April 2003.

·        For family members of an index case with a known mutation, a single site analysis is provided for that mutation for $325 ($490 for results in 10 days).

·        For others, a comprehensive full sequence determination is provided in both forward and reverse directions for $2,760 ($4,140 for results in 10 days).  Beginning in August 2002, this analysis also includes detection of five large recurrent rearrangements.  For patients who have previously tested negative by the comprehensive full sequencing, this panel of rearrangements can be ordered for $325.

·        For Ashkenazi Jewish individuals, testing is provided for three specific mutations (187delAG and 5385insC in BRCA1, and 6174delT in BRCA2) for $385 ($575 for results in 10 days).  This type of testing can also be obtained at other licensed clinical laboratories in the United States  

Polymorphism studies
In an effort to enhance the utilization of BRCA1/2 mutation test results, Myriad Genetic Laboratories has collaborated with investigators to analyze recurrent variants of uncertain clinical significance in control populations.  Those variants identified in the control population at a frequency of two percent are reclassified to polymorphisms of no clinical significance.  Amended reports are issued for all patients whose interpretation changes.  This ongoing effort continues to reduce the number of indeterminate test results.   

Family member testing for uncertain variants
In order to further characterize variants of uncertain clinical significance, Myriad Genetic Laboratories will test additional relatives of the proband for the specific variant identified, in order to determine whether it is co-segregating with cancer in her or his family.  This analysis is offered without charge to either parent of the proband, any relative with invasive breast cancer diagnosed before age 60, and any relative diagnosed with ovarian cancer or male breast cancer at any age.  Health care providers are given a report with the test result that outlines the option of testing additional family members.  This report summarizes additional information about the uncertain variant, such as the total number of observations, the most common ancestry of the patients, the number of different deleterious mutations seen in the same gene, and whether the variant does not co-segregate with cancer in at least two families.  In general, variants that are observed with deleterious mutations in the same gene, and/or do not consistently co-segregate with cancer, are more likely to be of limited clinical significance than to be deleterious. 

Changing the status of a mutation
An uncertain variant can be reclassified as a polymorphism of no clinical significance if:

§         it is found in two percent of a control population, or

§         it is found in equal or greater percentage of a control population, and it does not co-segregate with disease in multiple families, and/or it has been seen with a deleterious mutation in the same gene, or

§         it has been shown to have no clinical significance in an association study. 

An uncertain variant can be reclassified as a deleterious mutation if:

§         it has been statistically linked to cancer in a family, or

§         it is an evolutionarily conserved amino acid and the mutant amino acid is chemically different from the wild-type amino acid.