Today, there are hundreds of Genetic tests, some of them for relatively common disorders, such as cystic fibrosis, and others for very rare diseases. A genetic test is fundamentally different from other kinds of diagnostic tests you might take. Indeed, a whole new field, genetic counseling, has grown up around the need to help incorporate family history and genetic testing into modern health care.
The purposes of genetic tests vary. Some genetic tests are used to confirm a preliminary diagnosis based on symptoms. But others measure your risk of developing a disease, even if you are healthy now (presymptomatic testing), or determine whether you and your partner are at risk of having a child with a genetic disorder (carrier screening).
As the name suggests, a genetic test looks at your genes, which consist of DNA (deoxyribonucleic acid). DNA is a chemical message to produce a protein, which has a specific function in the body. Proteins are essential to life—they serve as building blocks for cells and tissues; they produce energy and act as messengers to make your body function. In addition to studying genes, genetic testing in a broader sense includes biochemical tests for the presence or absence of key proteins that signal aberrant gene function.
A genetic test checks the DNA of your cells. It can find changes in your genes, or it can check the number, order, and structure of your chromosomes. Testing may be done on samples of body tissue, blood, or other body fluids such as urine or saliva. You inherit half of your genetic information from your mother and the other half from your father. Genes determine things such as your blood type, hair color, and eye color, as well as your risk for certain diseases. Testing can find gene or chromosome changes that may cause medical problems.
Why It Is Done
- Find out if you carry a gene for an inherited disease such as Tay-Sachs disease or cystic fibrosis. This is called carrier identification. In families that have these diseases, some people don’t get the disease, but they carry a gene that they could pass on to their children. Finding out if you’re a carrier can help you make decisions about having children.
- Find out if your fetus has a genetic disorder or birth defect such as Down syndrome. This is called prenatal testing. It can help you make decisions about your pregnancy.
- Check your baby for certain diseases, such as PKU. This is called newborn screening. This information can help guide treatment if your baby has a disease.
- Find out if you carry a gene that increases your risk for a disease later in life, such as breast cancer or Huntington’s disease. This is called late-onset disease testing. This may be important if a close relative has such a disease. The information might help you take steps to prevent the disease. Or it can help you make decisions about having children.
- Find out if you have an inherited heart disease called hypertrophic cardiomyopathy. You may want to have this test if a close relative has the disease.
- Check for genetic changes that may affect your treatment. Testing may help your doctor find out if a blood thinner will work for you. Or it can help your doctor suggest the best treatment for a disease such as HIV or some cancers.
How To Prepare
You do not need to do anything special to prepare for this test.
Talk with your doctor if you have any concerns about the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
The information found by a genetic test can have a huge impact on your life. So before you have the test, you may want to talk to a genetic counselor or a doctor who specializes in genetics (geneticist). Genetic counseling can help you understand your genetic risks and decide if you want testing.
How It Is Done
A genetic test can be done using almost any cell or tissue from the body.
Blood sample from a heel stick
For newborn testing, the blood sample is usually taken from the baby’s heel instead of a vein. The health professional doing the heel stick will:
- Clean your baby’s heel with alcohol. Then he or she will prick the heel with a sharp tool called a lancet.
- Collect several drops of blood inside circles on a special piece of paper.
- Put a small bandage on the site.
Blood sample from a vein
The health professional taking a sample of your blood will:
- Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
- Clean the needle site with alcohol.
- Put the needle into the vein. More than one needle stick may be needed.
- Attach a tube to the needle to fill it with blood.
- Remove the band from your arm when enough blood is collected.
- Put a gauze pad or cotton ball over the needle site as the needle is removed.
- Put pressure on the site and then put on a bandage.
Cell sample from a fetus
Cells are collected using amniocentesis or chorionic villus sampling.
To learn more, see:
- Chorionic Villus Sampling.
How It Feels
Blood sample from a heel stick
Your baby may feel a little discomfort when the skin is pricked.
Blood sample from a vein
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.
Saliva, urine, or semen sample
It is not painful to collect a saliva, urine, or semen sample.
Blood sample from a heel stick
There is very little chance of a problem from a heel stick. A small bruise may form at the site.
Blood sample from a vein
There is very little chance of a problem from having a blood sample taken from a vein.
- You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
- In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. You can use a warm compress several times a day to treat this.
Bleeding can be a problem for people who have bleeding disorders or take blood-thinning medicines such as aspirin or warfarin (Coumadin). If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
Saliva, urine, or semen sample
Collecting a saliva, urine, or semen sample does not cause problems.
The information from a genetic test can affect you and your family in many ways. For example, it may have an impact on:
- Your emotions and relationships. You may feel anxious or depressed if you learn that you are likely to have a serious disease or have a child who has a disease. This news may also affect your relationship with your partner or other family members.
- Your treatment choices. If you test positive for a disease-specific gene change (mutation), you may decide to use preventive or treatment options, if they are available. They can help to reduce the impact or severity of the disease. While many treatment options have been proven to work well, others may be harmful or may not work.
- Your pregnancy decisions. Genetic testing can help you make decisions about your pregnancy or plan for the future. If you find out that your fetus has a genetic disease, you may decide to end the pregnancy. Or you may change your delivery plans. If your baby is likely to need special care after birth, you may need to deliver in a hospital that can provide this care.
- Your privacy. Many people worry that their genetic information might affect their job options or their ability to get insurance. But the United States has a law called the Genetic Information Nondiscrimination Act of 2008 (GINA). GINA prevents employers and health insurancecompanies from using a person’s genetic information in employment or coverage decisions. This law does not cover life insurance, disability insurance, or long-term care insurance.
Genetic counseling is recommended before you have genetic testing. It can help you understand and make decisions about testing.
A genetic test checks the DNA of your cells. It can find changes in your genes, or it can check the number, order, and structure of your chromosomes.
The results of genetic testing depend on the type of test done. Genetic testing may be used to:
- Find out if your fetus has a genetic disease or birth defect.
- Find out if you have an inherited disease.
- Give information about how likely it is that you will have a disease in the future.
- Find out if you are a carrier of a genetic disease.
- Help choose the right treatment for some diseases, such as HIVinfection or some types of cancer.
What Affects the Test
You may not be able to have the test, or the results may not be helpful, if you have a blood transfusion within a week before the test.
What To Think About
The information found by a genetic test can have a huge impact on your life. So before you have the test, you may want to talk to a genetic counselor or a doctor who specializes in genetics (geneticist). Genetic counseling can help you understand your genetic risks and decide if you want testing.
- A prenatal test may find a serious inherited disease or disorder (such as Down syndrome). This would greatly impact both you and your child. You may want to think ahead to what you might do if the test finds a serious problem.
- The results of the test are protected under the Health Insurance Portability and Accountability Act (HIPAA). HIPAA requires that providers, such as doctors, nurses, and hospitals, keep your health information private. Your privacy should be maintained, and your information should only be released to those who are authorized to have it.
- Finding out that you have a genetic disease should not affect your ability to get a job or get health insurance. In the United States, there is a law called the Genetic Information Nondiscrimination Act of 2008 (GINA). It protects people who have DNA differences. This law does not cover life insurance, disability insurance, or long-term care insurance.
- A genetic test can sometimes reveal information you didn’t expect, such as the identity of a child’s father (paternity).
There are other types of genetic tests that you might want to think about. For example:
- A karyotype test can be used to check the size, shape, and number of chromosomes. Extra or missing chromosomes, or abnormal positions of chromosome pieces, can cause problems with a person’s growth, development, and body functions. To learn more, see the topic Karyotype Test.
- A breast cancer (BRCA) gene test is done to check your risk of getting breast cancer. To learn more, see the topic Breast Cancer (BRCA) Gene Test.
- A type of genetic test called DNA fingerprinting can be used to find out who a child’s father is, to help solve crimes, or to identify a body. This test is more accurate than dental records, blood type, or actual fingerprints. To learn more, see the topic DNA Fingerprinting.
What do Genetic Tests Test For?
Long strings of DNA condense together, packaging the DNA in the form of a chromosome. Most people have 23 pairs of chromosomes in the nucleus of each cell. One of each chromosome pair is inherited from the mother and the other is inherited from the father. Some tests look at chromosomes for abnormalities such as extra, missing or transposed chromosomal material. The chromosomes hold 20,000 to 25,000 genes, meaning that each chromosome is densely packed with genes. Extra or missing pieces of chromosomes can have a significant impact on the health of an individual. Also, sometimes pieces of chromosomes become switched, or transposed, so that a gene ends up in a location where it is permanently and inappropriately turned on or off. The genes on the chromosomes are responsible for making proteins, which direct our biological development and the activity of about 100 trillion cells in our bodies.
If something goes wrong with an essential protein, the consequences can be severe. For example, a protein called alpha-1 antitrypsin (AAT) clears the lungs of a caustic agent called neutrophil elastase. If the body has an alteration in the gene that makes the protein AAT, the AAT protein may not be made correctly or at all. Then neutrophil elastase will build up in the lungs, and the individual can develop emphysema and other complications.
Most genetic conditions are the result of mutations in the DNA, which alter the instructions for making a given protein. Some mutations are inherited on genes passed down from parents, while others occur during an individual’s lifetime. These mutations can lead to diseases ranging from those we think of as “genetic diseases,” such as cystic fibrosis or AAT deficiency, to those we think of as degenerative diseases, such as heart disease. In the case of diseases like heart disease, asthma ordiabetes, a combination of factors—some genetic, some related to environmental or lifestyle—may work together to trigger the disease.
It’s possible to have a mutation, even one for a severe disease, such as cystic fibrosis (CF) and never know it. Almost all humans have two copies of each chromosome and therefore have two copies of each gene, one inherited from the mother and the other from the father. If only one copy of a given gene has a mutation, you are a healthy carrier of the disorder. You “carry” the mutation but do not have the disease. If both copies of a gene have a mutation, you will have the disease. Such disorders are called autosomal recessive. If you are a carrier, the unaltered gene in the pair retains the function. Those who are diagnosed with a recessive disease have inherited two copies of a gene, both carrying a mutation. Therefore, since one of those copies came from the mother and the other from the father, both parents must have at least one copy of the gene with a mutation. If two carriers of the same disease-causing gene have children, each pregnancy has a 25 percent chance of having the disease (because of a 25 percent chance of inheriting both the mother’s and the father’s mutated copies of the gene), a 50 percent chance of being a carrier and a 25 percent chance of not inheriting the mutation at all.
Some disorders, such as Huntington disease, are autosomal dominant. If a person has one mutated gene, its effects will cause the disease, even if the matching gene is normal. Thus, each child of a parent with Huntington disease has a 50 percent chance of inheriting the gene causing the disease. Osteogenesis imperfecta, which causes brittle bones, is another example of a dominant disorder.
Chromosomes can be one of two types: sex chromosomes or autosomes. Sex chromosomes are X and Y. Most men have an X and a Y, and most women have two Xs. If each parent contributes an X chromosome, the child is a girl; if the father passes on his Y chromosome, the child is a boy. Because girls have two X chromosomes, and therefore two copies of every X-linked gene, they are less likely than boys to have symptoms from X-linked genetic diseases because boys don’t have a backup copy if an X-chromosome gene has a mutation. Examples of X-linked diseases include forms of hemophilia and fragile X syndrome (the most common inherited cause of mental impairment). Autosomes are the remaining 22 pairs of chromosomes. Therefore, most diseases are autosomal, or due to genes on the autosomes.
What Genetic Tests Can Find
Although genetic testing can be very useful in diagnosis, prevention and medical decision-making, genetic tests do not always provide clear answers. One such result is a “variant of uncertain significance.” All people have differences in their DNA, so if a new DNA alteration is detected, it may be uncertain as to whether it is associated with disease or is part of normal human variation. Another limitation is that not all genetic tests are created as equals. Since genetic testing can be very expensive, some tests only look for the most common disease-causing mutations. Instead of examining the entire gene, these tests only look for specific, common mutations. If you or your family has a mutation in a portion of the gene that wasn’t tested, you will have a negative result, even though you do have a disease-associated mutation. Since genetic tests are not perfect, it is always important that genetic test results be interpreted in combination with medical and family history by a genetic counselor or other genetics-credentialed professional.
The Cost of Genetic Testing
The cost of a genetic test varies dramatically, ranging from $100 to more than $3,200. The difference stems largely from the variation in labor intensity of different tests. Some tests look for a limited number of mutations (sometimes only one) known to cause a disease. This type of test may only look at one piece of DNA code, for one specific mutation. Other genetic tests require sequencing of the entire gene, where they examine each piece of DNA code comprising the gene, which can be thousands of pieces of code.
The explosion of genetic research now taking place is expected to bring prices down and dramatically increase the number of tests available. Tests are becoming available to predict your genetic risk of more common disease, such as heart disease and diabetes. This information will help you and your health care professional develop specific strategies for prevention. Preventive efforts can include changing your lifestyle or perhaps taking certain medications, which may be tailored to your specific genetic profile, and early screening to head off the worst complications should you develop the disease.
What Is Genetic Counseling?
Because the nature of genetic testing is so complex, with implications for both the person being tested and his or her family, genetic counseling is an important part of pre- and post-genetic testing. Unlike most medical appointments, a counseling session may be a family affair, with participation of all concerned relatives.
A genetic counselor is a health care professional who is an expert in counseling, human genetics and genetic testing. He or she reviews your family and medical histories to determine if there appears to be a hereditary pattern of disease. A genetic counseling session can last any amount of time, depending upon the situation. Genetic counseling typically includes:
- gathering background medical information about you and your family
- risk assessment for having a genetic disease or mutation
- discussion about genes that may be appropriate for testing, if indicated
- discussion about the risks, benefits and limitations of testing
- providing information on inheritance, the genetic testing procedure, the possible results and what they mean
- informed consent, if genetic testing is indicated and you elect to have it
Genetic counseling will educate you so you can make an informed decision. Genetic counselors are trained to assist you in the decision-making process, and genetic testing is never required.
Because family history is so crucial in assessing for a genetic condition and determining which genes to consider testing, a counselor may request medical records to confirm a diagnosis, especially if you’re trying to determine whether a family pattern of Cancer is hereditary.
Family member recollections can be inaccurate—who had which disease or even what type of disease. Many conditions either were not discussed or not diagnosed in past decades. A genetic counselor can listen to a family account and help tease out details to better identify potential patterns.
Genetic counselors are committed to protecting the privacy of their patients. They will not contact other family members without your permission, though they may encourage you to share results that might affect the health of your relatives. The Genetic Information Nondiscrimination Act of 2008 (GINA) is a new federal law that specifically addresses genetic discrimination in regard to health insurance and employment. The law took effect in 2009.
How to Find a Counselor
The core credentials are a master’s degree in the field and certification conferring the designation of certified genetic counselor (CGC).
Characteristics of Carriers
Genes come in matched pairs, except for those on the sex chromosomes. In the case of autosomal recessive disorders, if only one copy of the gene is damaged, the unaffected gene can still function, usually preventing symptoms of the disease. In fact, a disease-causing mutation can be inherited through dozens of generations of a family without anyone showing symptoms of the disease.
If two carriers of the same mutated gene have a child, the chance of both parents passing on his and her mutated copy is 25 percent, in which case the child would have the disease. There is also a 25 percent chance that both parents would pass on their unaffected genes, in which case the child would not have the disease and would not be a carrier. Finally, there is a 50 percent chance that the child will be like the parents and will be a healthy carrier (with one unaffected gene and one with a mutation, but not developing the disease).
The exception to this pattern occurs if a disorder is recessive and X-linked. The X is the symbol for the larger sex chromosome. A child who inherits two X chromosomes is a girl. A child with an X chromosome and a Y chromosome is a boy. If a mother has a disease-linked recessive mutation on one of her X chromosomes, she is a carrier of the disorder but should have no or minimal symptoms herself since she has an unaffected X, usually preventing the development of the disease. If the mother who carries an affected X has a son, he will have a 50 percent risk of inheriting the disorder because he will inherit either the mother’s affected X or unaffected X. If a male inherits the mother’s X which carries a mutation, and since a male has no second X chromosome (instead he has Y chromosome, hence being a male), he will then develop the disease. A daughter will have a 50 percent chance of being a carrier, like her mother, since she has inherited her second, functional X from her father.
Fragile X syndrome, as its name suggests, is one such X-linked disorder. The severity of Fragile X can greatly vary. Boys who inherit the mutation usually develop the disease, the most common form of genetically inherited mental retardation. Girls who inherit a fragile X mutation are more likely to be carriers, although some females do develop symptoms. If you have a family history of mental retardation, testing can determine whether a Fragile X mutation is responsible and whether you are a carrier.
As with other types of testing, genetic counseling can help you understand carrier screening. A counselor can also help you develop strategies for sharing the information with other family members who may also be at risk of carrying the mutation.
Why Have Carrier Screening?
Carrier screening is recommended for any disorder or mutation that has been identified in a family member. In addition, you should consider carrier screening for mutations found frequently in your particular ethnic group. The prevalence of genetic disorders is linked closely to ethnic heritage. Caucasians, for example, have a much higher risk than most other groups for cystic fibrosis, and those of African American descent are more likely to be carriers of sickle cell anemia mutations.
Most carrier screening tests don’t sequence an entire gene. Instead they focus on specific mutations known to be common in particular groups. The results are generally accurate (90 to 95 percent). Since most genetic screening tests only look for the common mutations, there is a residual risk that there is a less common mutation that wasn’t tested.
The following are some examples of ethnicities and the conditions that are found more frequently in those groups.
- Caucasians: phenylketonuria, hemochromatosis, cystic fibrosis and alpha 1-antitrypsin deficiency.
- African Americans: sickle cell disease and thalassemia
- East Asians (except Koreans): thalassemia
- Irish, French Canadians and Cajuns: Tay-Sachs disease
- Mediterraneans: thalassemia and familial Mediterranean fever
- Southeast Asians (Cambodians, Laotians and Vietnamese): hemoglobinopathies (disorders of hemoglobin, the oxygen-carrying component of red blood cells)
There are also “genetic screening panels.” A panel is typically used for individuals of a specific ethnicity that have a risk for several associated genetic conditions or common mutations for which genetic tests can be performed at one time. One example of a screening panel is the Ashkenazi Jewish Screening Panel. The Ashkenazi Jews are of Central and East European descent, and they account for about 80 percent of the Jewish population in the United States.
The Ashkenazi Jewish screening panel varies depending on the program and laboratory. Some test only for Tay-Sachs and Canavan diseases; other panels may include disorders such as Gaucher disease, Bloom syndrome, Fanconi anemia, Niemann-Pick disease, hereditary deafness and familial dysautonomia. Many panels also include a screen for cystic fibrosis (CF). This condition is not more common in the Ashkenazi population. Caucasians are actually more likely to carry CF mutations than other groups. Still, the ratio of the Ashkenazi population that carries known CF mutations is fairly high, about one in 25. Three specific mutations are common in this population, making testing more specific.
Experts Recommend Preconception Screening
You might think that if you and your partner come from different backgrounds, carrier screening is unnecessary. The American College of Obstetricians and Gynecologists, however, advises that if one partner in a couple is at high risk and the other is not, the high-risk partner should be screened. If that person tests positive as a carrier, the other partner should be screened.
Genetics experts recommend carrier screening before a couple plans to conceive. Be proactive in seeking preconception genetic counseling. It ensures you the most options, and your genetic counselor can guide you through which screening tests are most appropriate.
If two prospective parents are found to be carriers of a disease, their options include:
- use of donor sperm or a donor egg
- in vitro fertilization and preimplantation genetic diagnosis of the embryos
- prenatal testing (If a fetus is identified to carry mutations that could cause disease or disability, some individuals decide to end the pregnancy, while others use the information to prepare for a child having the genetic condition.)
For some recessive diseases, even though an individual has two mutated genes, the clinical severity can vary from patient to patient. Someone with particular disease mutations, for example, may not have symptoms until middle age or may go a lifetime asymptomatic, making decisions about testing—and what to do if a fetus turns out to be affected—difficult for prospective parents. It is very important to discuss the details of your genetic test results with a clinician who specializes in interpreting results.
Testing for Inherited Cancer
If you have a family history of cancer, particularly cancers that occur before age 50, you may want to explore cancer genetic counseling. Approximately 5 percent to 10 percent of cancers are due to a specific inherited gene mutation that increases cancer risk. Hereditary cancers are not always obvious. A mutation that leads to breast cancer in your grandmother may lead to ovarian cancer in your aunt. Likewise, a mutation that causes colon cancer in your sister may cause endometrial cancer in your daughter.
To determine whether your family’s cancers might be hereditary, a genetic counselor will need to know medical details about the family, especially those who have been diagnosed with cancer. Two important things to know about your relatives who have had cancer are: age at diagnosis and the exact organ where the cancer originated. Be prepared for a counselor to request medical records. One of several conclusions may be made about your family history:
- The cancers in the family, even if there are several, may be “sporadic” and it is highly unlikely that they are due to inherited genetic mutation.
- The pattern fits a known hereditary cancer syndrome for which genetic testing is available. Those who test positive for the mutation would need to be vigilant about prevention and screening measures. If a mutation has been identified in the family and an individual is negative, that person can be managed similar to others who do not have a mutation. If a mutation has not been identified in a family, yet the family history is still consistent with a hereditary cancer syndrome, your providers will tailor your screening and management plan accordingly.
- Family history is somewhat suggestive of an inherited pattern, but is not consistent with a known hereditary cancer risk syndrome. In this situation, the screening and prevention methods are tailored to the family history of cancer.
Some inherited cancer syndromes for which testing is available are:
- Hereditary breast and ovarian cancer syndrome (HBOC) is caused by mutations in the BRCA1 or BRCA2 genes and is often referred to as the “breast cancer genes.”BRCA1 and BRCA2 mutations are mostly associated with breast and ovarian cancer. Some families also exhibit other cancers such as male breast cancer, pancreatic cancer, melanoma, gastric cancer, prostate cancer and others.
- Lynch syndrome can be caused by mutations in the MLH1, MSH2 and MSH6genes. Such mutations are also linked to cancers of the endometrium, stomach, small bowel, ureter, ovary and collecting system of the kidneys. This syndrome is sometimes known as hereditary non-polyposis colorectal cancer, although this term is misleading because people with Lynch syndrome do develop polyps.
- Familial adenomatous polyposis (FAP), or attenuated familial adenomatous polyposis (AFAP), is caused by a mutation in the APC gene. Typical FAP results in the growth of hundreds or thousands of polyps in the colon beginning at young ages, sometimes in the teens. AFAP is also due to a mutation in the APC gene, but individuals have fewer polyps.
- Ataxia telangiectasia is a complex autosomal recessive disorder caused by an ATM(ataxia telangiectasia mutated) gene. Among other effects, including dysfunction of the cerebellum (the part of the brain that controls motor function and balance), A-T has been linked to lymphomas and leukemia. It is diagnosed in childhood. As individuals live longer, other cancers have been observed, including ovarian and breast cancers, stomach cancer and melanoma.
- Multiple endocrine neoplasia (MEN) 1 and 2 are two separate rare disorders caused by mutations in the MEN1 or RET genes, respectively; MEN1 or 2 can lead to cancer in one of the endocrine glands, such as the parathyroid, thyroid, pancreas, pituitary or adrenal gland.
Your body has certain genes that regulate when your cells divide and how often they divide. You were born with two copies of each cell control gene, one inherited from your mother and one from your father. Most mutations occur accidentally as part of natural aging. If a mutation occurs on one copy of a given cell-control gene, the second copy remains functional. But if the second copy of a cell-control gene develops a mutation, that cell loses its ability to control cell division, potentially resulting in a tumor and possibly cancer. Cancers are typically due to accidental or sporadic mutations that occur throughout a lifetime.
Some people inherit a copy of a cell control gene that already has a mutation. These individuals still carry a functioning copy of the cell control gene, which can still regulate the cell growth. Over time, the unaffected gene may develop a sporadic mutation, resulting in both copies functioning improperly, allowing that cell to become cancerous and multiply. Inheriting a mutation associated with cancer does not cause the cancer.
Not everyone with a hereditary cancer predisposition mutation will develop cancer. For those who carry a cancer predisposition mutation, the risks vary greatly and depend upon the specific gene and syndrome. Those with a BRCA mutation face a lifetime breast cancer risk of up to 88 percent, compared to about 13 percent in the general population, and a lifetime ovarian cancer risk of up to 60 percent, compared to a population risk of about 1.4 percent.
The knowledge that you are positive for a mutation allows you to take action to reduce your risk through preventive measures, such as more frequent screening to detect early growths or tumors, taking protective medications or even prophylactic surgery to remove the organ prone to cancer.
Other Predisposition Syndromes
These are only a few examples of cancer predisposition syndromes. You may want to consider genetic counseling if one of the following are true:
- Three or more blood-related individuals in your family have the same or related cancers.
- You have early onset of a cancer
- You have more than one diagnosis of cancer.
Breast Cancer Screening
Are You A Candidate For Breast Cancer Testing?
Because breast cancer is one of the most common cancers, many individuals are becoming aware of genetic testing for BRCA mutations. BRCA testing is not appropriate for most people.
If you think there’s a possibility that your family has a hereditary cancer pattern, talk to a genetic counselor. The genetic counselor will assess the likelihood for you to carry a cancer predisposition mutation and, if indicated, discuss the option of genetic testing.
You might want to seek genetic counseling and breast and ovarian cancer risk assessment if you have one of the following:
- Breast cancer at an early age
- Two primary breast cancers or breast cancer and an incidence of ovarian, fallopian tube or primary peritoneal cancer
- Two or more primary breast cancers or breast cancer and ovarian, fallopian tube or primary peritoneal cancers in one or more close relatives from the same side of the family (maternal or paternal)
- A combination of breast cancer with one or more of the following: thyroid cancer, sarcoma, adrenocortical carcinoma, endometrial cancer, pancreatic cancer, brain tumors, diffuse gastric cancer, dermatological manifestations or leukemia/lymphoma on the same side of the family
- Member of the family with a known mutation in a cancer susceptibility gene
- Any male breast cancer
- Any ovarian, fallopian tube or primary peritoneal cancer
Your ethnic background may come into play with breast cancer risk as well, if you are of Ashkenazi Jewish descent. Women with such a background are about 10 times more likely to have a mutation than women in the general population. If you are of Ashkenazi Jewish descent, you may also consider genetic counseling if there is any family history of breast or ovarian cancer. An Ashkenazi Jewish BRCA testing panel is available. This test looks for three specific mutations that account for 90 percent of the positive BRCA1/2 gene changes in this population. If the test is negative, BRCAsequence analysis may be ordered. As you think about your family history, keep in mind that these mutations can be inherited maternally or paternally. Be sure to look at your father’s family history, in addition to your mother’s.
It is important to remember that even when a family has a mutation, not everyone will inherit it. For example, if your father carries a BRCA1 mutation , he still has an unaffected copy of BRCA1. It depends on which gene is inherited by each child, and there is a 50 percent chance that each child will inherit the BRCA mutation. Thus, in a group of siblings, some may inherit a mutation, while others may not.
BRCA testing has several limitations. Not all families that have cancers consistent with a BRCA mutation will test positive. This is because it is believed that there are other genes involved with breast and ovarian cancer risk. It is suspected that approximately 16 percent of HBOC families have mutations in genes other than BRCA1 and BRCA2 . For this reason, it is ideal to test the person in the family who is most likely to test positive, to confirm whether a mutation can be identified. Another limitation of this test is that sometimes people receive an “uncertain” result. No matter whether the result is positive, negative or uncertain, your genetic counselor will thoroughly explain the results and what it means for you and your cancer risk.
There are several other cancer syndromes that have breast cancer as a feature. For this reason, the family history information is crucial. It can greatly change what gene may be suspected. Pathology reports, medical records and even death certificates can be useful for your genetic counselor.
Several variations of BRCA testing are available. Your genetic counselor can help determine which is most appropriate.
Comprehensive sequence analysis of BRCA1 and BRCA2 costs about $3,120. If a mutation is identified in the first person tested, subsequent tests for other family members are approximately $440 each. The reason the first test is so expensive is that the genes must be fully sequenced to identify the mutation. Once a mutation is found, the technicians know where exactly to look in the other relatives’ DNA samples. Those of Ashkenazi Jewish descent (Eastern European background) may be tested using theBRCA Ashkenazi panel, examining three specific mutations most commonly found in this population, which costs approximately $535. A new addition to BRCA testing became available in 2006. This test looks for large deletions and duplications of theBRCA genes. This test is called BART and costs $650.
Again, it is important to regularly contact your genetic counselor to update your family history. New genetic testing becomes available over time. Also, learning of additional family members and their cancers may change your genetic assessment and lead to considering testing for a different gene.
If no one in your family has been diagnosed with breast or ovarian cancer, then your risk of carrying a BRCA1/2 mutation is quite low and testing would not be recommended. Keep in mind, however, that absence of these mutations doesn’t mean you won’t develop cancer. At least 90 percent of breast and ovarian cancer cases are “sporadic,” meaning they don’t stem from inherited mutations, but rather are caused by a mutation or a combination of mutations that arise over time. Therefore, regardless of your genetic status, be sure to follow the recommendations of your health care professional, such as having an annual breast examination by your health care professional (called a clinical breast examination) and a mammogram, if appropriate (schedule based on age).
Finally, if you test negative, you should still be assessed for cancer risk, based on your family history and medical history. This information can help determine whether you are at average risk, using general screening guidelines, or whether your screening regimen should be tailored to you.
Did You Test Positive?
If you test positive for a BRCA mutation, there are options for minimizing your cancer risk, but none of them reduce your risk to zero. No individuals are the same, and you should ask your health care professional to help you weigh the risks and benefits for each of the following options.
- Breast self-exam training and education, starting monthly breast self-exams at age 18.
- Clinical breast exam, semiannually, starting at age 25.
- Annual mammogram and breast MRI starting at age 25.
- Risk-reducing mastectomy.
- Risk-reducing salpingo-oophorectomy (removal of ovaries and fallopian tubes), ideally between 35 and 40 years old, or upon completion of child bearing, or individualized based on earliest age of onset of ovarian cancer in the family.
- For those who have not elected salpingo-oophorectomy, concurrent transvaginal ultrasound and CA-125 (a blood test that may indicate certain cancers) every six months starting at age 35, or 5 to 10 years earlier than the earliest age of diagnosis of ovarian cancer in the family.
- Chemoprevention options, such as tamoxifen and raloxifene. These medications are typically used after breast cancer to reduce the risk for another breast cancer, but in high-risk individuals, they can be offered to reduce the risk for an initial breast cancer.
- Investigational imaging and screening studies, when available.
Oophorectomy is increasingly being recommended for women who test positive forBRCA mutations and are either finished with childbearing or are certain that they do not want children. Removal of the ovaries not only reduces ovarian cancer risk 80 percent or more in both pre- and post-menopausal women, it also reduces breast cancer risk 50 percent in premenopausal women. That’s because the ovaries produce estrogen, which stimulates breast growth and is linked to cancer risk. Removing the ovaries also removes your body’s source of estrogen. Therefore, estrogen levels diminish rapidly and trigger menopausal symptoms, such as hot flashes, vaginal dryness and bone loss, among other short-term physical and emotional changes and long-term health risks associated with menopause. For some women, “surgical menopause,” through removal of the ovaries, can trigger more sudden and severe menopausal symptoms than when menopause occurs spontaneously at the end of a woman’s childbearing years—a transition that typically takes about five years in a woman’s late 40s.
Postmenopausal hormone therapy (often referred to as hormone replacement therapy or HRT) can be prescribed prior to or just after surgery to mitigate menopausal symptoms. However, women, health care professionals and the federal government are scrutinizing the use of postmenopausal hormone therapy more closely than ever before and its safety for both long-term and short-term use is in question.
The U.S. Food and Drug Administration (FDA) now requires a highlighted and boxed warning on all estrogen projects for use by postmenopausal women. The so-called “black box” is the strongest step the FDA can take to warn consumers of potential risks from a medication. The warning highlights the increased risk for heart disease, heart attacks, stroke and breast cancer from supplemental estrogen—risks illuminated by part of the Women’s Health Initiative study, which was abruptly halted when the risks were identified.
The “black-box” warning also advises health care professionals to prescribe estrogen products at the lowest dose and for the shortest possible length of time. Women taking estrogen projects are cautioned to have yearly breast exams and receive periodic mammograms.
Because every woman’s risk profile is different, women who are thinking about taking postmenopausal hormone therapy or are currently taking it, need to review their options and treatment plans with their health care professional in light of the FDA’s warning. Since then, new lower-dose versions of the hormone therapies used to treat symptoms of menopause have been developed. The FDA approved a low-dose version of the combination estrogen-progestin treatment Prempro and the estrogen-only Premarin.
Colon Cancer Screening
Are You A Candidate For Colon Cancer Testing?
One colorectal cancer predisposition syndrome is Lynch Syndrome (otherwise known as hereditary nonpolyposis colon cancer). The syndrome increases lifetime risk of colorectal cancer to 80 percent vs. a 5.4 percent population risk and also elevates your risk of endometrial cancer, ovarian cancer and gastric cancer. Those with Lynch Syndrome also face a higher risk of cancers of the kidney and ureter, liver, brain, pancreas, stomach and small bowel. Sometimes before genetic testing is performed, a preliminary test on the actual cancer tumor can help suggest whether genetic testing is indicated, and if so, which gene to test.
Other examples of colorectal cancer predisposition syndromes are FAP, AFAP and MYH-associated polyposis. Several other syndromes are also associated with colorectal cancer risk.
To determine whether testing might be appropriate for your family, a genetic counselor would look for the number of cancers in your family, ages of onset, the specific types of cancer and the family’s history of colon polyps. Pathology reports are quite useful, because the type of colon cancer, the types of polyps and the locations of cancer and polyps can help direct which genes should be tested. Many aspects of the testing parallel BRCA testing. For Lynch Syndrome, the ideal initial candidate for testing is a person who has been diagnosed with cancer. This test can cost approximately $3,640.
Screening options for those who have a colorectal cancer predisposition syndrome vary, depending on which gene may have a mutation. Some options may include the frequent c