Diagnosis of Cancer

Genetic Test Results

Genetic tests are usually requested by a person’s doctor or other health care provider. Genetic counseling can help people consider the risks, benefits, and limitations of genetic testing in their particular situations.

The results of genetic tests can be positive, negative, or uncertain. A genetic counselor, doctor, or other health care professional trained in genetics can help an individual or family understand their test results. These professionals can also help explain the incidental findings that a test may yield, such as a genetic risk factor for a disease that is unrelated to the reason for administering the test. And they can clarify the implications of test results for other family members.

Medical test results are normally included in a person’s medical records, particularly if a doctor or other health care provider has ordered the test or has been consulted about the test results. Therefore, people considering genetic testing should understand that their results may become known to other people or organizations that have legitimate, legal access to their medical records, such as their insurance company or employer, if their employer provides the patient’s health insurance as a benefit.

However, legal protections are in place to prevent genetic discrimination. The Genetic Information Nondiscrimination Act of 2008 is a federal law that prohibits discrimination based on genetic information in determining health insurance eligibility or rates and suitability for employment. In addition, because a person’s genetic information is considered health information, it is covered by the Privacy Rule of the Health Information Portability and Accountability Act of 1996.

Source: NCI (NIH)1

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Back to: « Cancer

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What is genetic testing?

Genetic testing looks for specific inherited changes (mutations) in a person’s chromosomes, genes, or proteins. Genetic mutations can have harmful, beneficial, neutral (no effect), or uncertain effects on health. Mutations that are harmful may increase a person’s chance, or risk, of developing a disease such as cancer. Overall, inherited mutations are thought to play a role in about 5 to 10 percent of all cancers.

Cancer can sometimes appear to “run in families” even if it is not caused by an inherited mutation. For example, a shared environment or lifestyle, such as tobacco use, can cause similar cancers to develop among family members. However, certain patterns—such as the types of cancer that develop, other non-cancer conditions that are seen, and the ages at which cancer typically develops—may suggest the presence of a hereditary cancer syndrome.

The genetic mutations that cause many of the known hereditary cancer syndromes have been identified, and genetic testing can confirm whether a condition is, indeed, the result of an inherited syndrome. Genetic testing is also done to determine whether family members without obvious illness have inherited the same mutation as a family member who is known to carry a cancer-associated mutation.

Inherited genetic mutations can increase a person’s risk of developing cancer through a variety of mechanisms, depending on the function of the gene. Mutations in genes that control cell growth and the repair of damaged DNA are particularly likely to be associated with increased cancer risk.

Genetic testing of tumor samples can also be performed, but this Fact Sheet does not cover such testing.

Source: NCI (NIH)2

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diagnosis:  The process of identifying cancer based on its signs and symptoms. A definitive diagnosis of cancer can only be made by a pathologist (see Pathology).

Source: Australian Institute of Health and Welfare3

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detection:  The process of identifying an abnormality of tissue or cells that may be cancerous.

Source: Australian Institute of Health and Welfare4

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Accurately diagnosing cancer can take weeks or months. As cancer often develops slowly over several years, waiting for a few weeks won't usually impact on the effectiveness of treatment.

The National Institute for Health and Care Excellence (NICE) has produced referral guidelines for suspected cancer.

You shouldn't have to wait more than two weeks to see a specialist if your GP suspects you have cancer and urgently refers you.

In cases where cancer has been confirmed, you shouldn't have to wait more than 31 days from the decision to treat to the start of treatment.

Source: NHS Choices UK5

Tests for Cancer

What genetic tests are available for cancer risk?

More than 50 hereditary cancer syndromes have been described. The majority of these are caused by highly penetrant mutations that are inherited in a dominant fashion. The list below includes some of the more common inherited cancer syndromes for which genetic testing is available, the gene(s) that are mutated in each syndrome, and the cancer types most often associated with these syndromes.

Hereditary breast cancer and ovarian cancer syndrome

  • Genes: BRCA1, BRCA2
  • Related cancer types: Female breast, ovarian, and other cancers, including prostate, pancreatic, and male breast cancer

Li-Fraumeni syndrome

Cowden syndrome (PTEN hamartoma tumor syndrome)

  • Gene: PTEN
  • Related cancer types: Breast, thyroid, endometrial (uterine lining), and other cancers

Lynch syndrome (hereditary nonpolyposis colorectal cancer)

  • Genes: MSH2, MLH1, MSH6, PMS2, EPCAM
  • Related cancer types: Colorectal, endometrial, ovarian, renal pelvis, pancreatic, small intestine, liver and biliary tract, stomach, brain, and breast cancers

Familial adenomatous polyposis

  • Gene: APC
  • Related cancer types: Colorectal cancer, multiple non-malignant colon polyps, and both non-cancerous (benign) and cancerous tumors in the small intestine, brain, stomach, bone, skin, and other tissues

Retinoblastoma

Multiple endocrine neoplasia type 1 (Wermer syndrome)

Multiple endocrine neoplasia type 2

Von Hippel-Lindau syndrome

Source: NCI (NIH)6

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How is genetic testing done?

Genetic tests are usually requested by a person’s doctor or other health care provider. Although it may be possible to obtain some genetic tests without a health care provider’s order, this approach is not recommended because it does not give the patient the valuable opportunity to discuss this complicated decision with a knowledgeable professional.

Testing is done on a small sample of body fluid or tissue—usually blood, but sometimes saliva, cells from inside the cheek, skin cells, or amniotic fluid (the fluid surrounding a developing fetus).

The sample is then sent to a laboratory that specializes in genetic testing. The laboratory returns the test results to the doctor or genetic counselor who requested the test. In some cases, the laboratory may send the results to the patient directly. It usually takes several weeks or longer to get the test results. Genetic counseling is recommended both before and after genetic testing to make sure that patients have accurate information about what a particular genetic test means for their health and care.

Source: NCI (NIH)7

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What do the results of genetic testing mean?

Genetic testing can have several possible results: positive, negative, true negative, uninformative negative, false negative, variant of unknown significance, or benign polymorphism. These results are described below.

A “positive test result” means that the laboratory found a specific genetic alteration (or mutation) that is associated with a hereditary cancer syndrome. A positive result may:

  • Confirm the diagnosis of a hereditary cancer syndrome
  • Indicate an increased risk of developing certain cancer(s) in the future
  • Show that someone carries a particular genetic change that does not increase their own risk of cancer but that may increase the risk in their children if they also inherit an altered copy from their other parent (that is, if the child inherits two copies of the abnormal gene, one from their mother and one from their father).
  • Suggest a need for further testing
  • Provide important information that can help other family members make decisions about their own health care.

Also, people who have a positive test result that indicates that they have an increased risk of developing cancer in the future may be able to take steps to lower their risk of developing cancer or to find cancer earlier, including:

  • Being checked at a younger age or more often for signs of cancer
  • Reducing their cancer risk by taking medications or having surgery to remove “at-risk” tissue (These approaches to risk reduction are options for only a few inherited cancer syndromes.)
  • Changing personal behaviors (like quitting smoking, getting more exercise, and eating a healthier diet) to reduce the risk of certain cancers

A positive result on a prenatal genetic test for cancer risk may influence a decision about whether to continue a pregnancy. The results of pre-implantation testing (performed on embryos created by in vitro fertilization) can guide a doctor in deciding which embryo (or embryos) to implant in a woman’s uterus.

Finally, in patients who have already been diagnosed with cancer, a positive result for a mutation associated with certain hereditary cancer syndromes can influence how the cancer is treated. For example, some hereditary cancer disorders interfere with the body’s ability to repair damage that occurs to cellular DNA. If someone with one of these conditions receives a standard dose of radiation or chemotherapy to treat their cancer, they may experience severe, potentially life-threatening treatment side effects. Knowing about the genetic disorder before treatment begins allows doctors to modify the treatment and reduce the severity of the side effects.

A “negative test result” means that the laboratory did not find the specific alteration that the test was designed to detect. This result is most useful when working with a family in which the specific, disease-causing genetic alteration is already known to be present. In such a case, a negative result can show that the tested family member has not inherited the mutation that is present in their family and that this person therefore does not have the inherited cancer syndrome tested for, does not have an increased genetic risk of developing cancer, or is not a carrier of a mutation that increases cancer risk. Such a test result is called a “true negative.” A true negative result does not mean that there is no cancer risk, but rather that the risk is probably the same as the cancer risk in the general population.

When a person has a strong family history of cancer but the family has not been found to have a known mutation associated with a hereditary cancer syndrome, a negative test result is classified as an “uninformative negative” (that is, does not provide useful information). It is not possible to tell whether someone has a harmful gene mutation that was not detected by the particular test used (a “false negative”) or whether the person truly has no cancer-predisposing genetic alterations in that gene. It is also possible for a person to have a mutation in a gene other than the gene that was tested.

If genetic testing shows a change that has not been previously associated with cancer in other people, the person’s test result may report “variant of unknown significance,” or VUS. This result may be interpreted as “ambiguous” (uncertain), which is to say that the information does not help in making health care decisions.

If the test reveals a genetic change that is common in the general population among people without cancer, the change is called a polymorphism. Everyone has commonly occurring genetic variations (polymorphisms) that are not associated with any increased risk of disease.

Source: NCI (NIH)8

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Who can help people understand their test results?

A genetic counselor, doctor, or other health care professional trained in genetics can help an individual or family understand their test results. Such counseling may include discussing recommendations for preventive care and screening with the patient, referring the patient to support groups and other information resources, and providing emotional support to the person receiving the results.

In some cases, a genetic counselor or doctor may recommend that other family members consider being tested for specific gene changes that indicate an increased risk of cancer. The decision to test other family members is complicated. It requires a careful evaluation of family history and other factors as well as advice from a genetic counselor or other professional trained in genetics. In general, physicians rely on the family member who has been tested to share the genetic information with their relatives so that family members will know that a genetic condition has been identified in their family. Then, each family member will need to make their own decision regarding whether or not to be tested themselves.

Source: NCI (NIH)9

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What are at-home or direct-to-consumer genetic tests?

Some companies offer at-home genetic testing, also known as direct-to-consumer (DTC) genetic testing. People collect a tissue sample themselves and submit the sample through the mail. They learn about the test results online, by mail, or over the phone. DTC genetic testing is often done without a doctor’s order or guidance from a doctor or genetic counselor before the test. Some states in the United States do not allow DTC genetic testing.

Whereas the genetic testing for cancer that is typically ordered by a doctor involves testing for rare major hereditary cancer syndromes, most DTC genetic testing for cancer risk involves the analysis of common inherited genetic variants, called single-nucleotide polymorphisms, that have been shown to be statistically associated with a particular type of cancer. Each individual variant is generally associated with only a minor increase in risk, and even when added together all the known variants for a particular cancer type account for only a small portion of a person’s risk of that cancer. Although the identification and study of such variants is an active area of research, genetic tests based on these variants have not yet been found to help patients and their care providers make health care decisions and, therefore, they are not a part of recommended clinical practice.

Even when people have DTC genetic tests for known mutations in genes associated with hereditary cancer syndromes, there are potential risks and drawbacks to the use of DTC testing. In particular, without guidance about genetic test results from an informed, genetically knowledgeable health care provider, people may experience unneeded anxiety or false reassurance, or they may make important decisions about medical treatment or care based on incomplete information.

Also, although some people may view DTC genetic testing as a way to ensure the privacy of their genetic test results, companies that offer DTC genetic testing do not always tell the consumer the details of their privacy policies. In addition, if people consult their doctor or other health care provider about the test results obtained from a DTC testing vendor, the results may become part of the patient’s medical record anyway. Also, companies that provide DTC testing may not be subject to current state and federal privacy laws and regulations. It is generally recommended that people considering DTC genetic testing make sure that they have chosen a reputable company.

The U.S. Federal Trade Commission (FTC) has a fact sheet about at-home genetic tests which offers advice for people who are considering such a test. As part of its mission, the FTC investigates complaints about false or misleading health claims in advertisements.

The American Society of Human Genetics, a membership organization of genetics professionals, has issued a statement about DTC genetic tests that recommends transparency in such testing, provider education about the testing, and the development of appropriate regulations to ensure test and laboratory quality.

Source: NCI (NIH)10

Screening Tests for Cancer

Who should consider genetic testing for cancer risk?

Many experts recommend that genetic testing for cancer risk should be strongly considered when all three of the following criteria are met:

  • The person being tested has a personal or family history that suggests an inherited cancer risk condition
  • The test results can be adequately interpreted (that is, they can clearly tell whether a specific genetic change is present or absent)
  • The results provide information that will help guide a person’s future medical care

The features of a person’s personal or family medical history that, particularly in combination, may suggest a hereditary cancer syndrome include:

  • Cancer that was diagnosed at an unusually young age
  • Several different types of cancer that have occurred independently in the same person
  • Cancer that has developed in both organs in a set of paired organs, such as both kidneys or both breasts
  • Several close blood relatives that have the same type of cancer (for example, a mother, daughter, and sisters with breast cancer)
  • Unusual cases of a specific cancer type (for example, breast cancer in a man)
  • The presence of birth defects, such as certain noncancerous (benign) skin growths or skeletal abnormalities, that are known to be associated with inherited cancer syndromes
  • Being a member of a racial/ethnic group that is known to have an increased chance of having a certain hereditary cancer syndrome and having one or more of the above features as well

It is strongly recommended that a person who is considering genetic testing speak with a professional trained in genetics before deciding whether to be tested. These professionals can include doctors, genetic counselors, and other health care providers (such as nurses, psychologists, or social workers). Genetic counseling can help people consider the risks, benefits, and limitations of genetic testing in their particular situation. Sometimes the genetic professional finds that testing is not needed.

Genetic counseling includes a detailed review of the individual’s personal and family medical history related to possible cancer risk. Counseling also includes discussions about such issues as:

  • Whether genetic testing is appropriate, which specific test(s) might be used, and the technical accuracy of the test(s)
  • The medical implications of a positive or a negative test result (see below)
  • The possibility that a test result might not be informative—that is, that the information may not be useful in making health care decisions (see below)
  • The psychological risks and benefits of learning one’s genetic test results
  • The risk of passing a genetic mutation (if one is present in a parent) to children

Learning about these issues is a key part of the informed consent process. Written informed consent is strongly recommended before a genetic test is ordered. People give their consent by signing a form saying that they have been told about, and understand, the purpose of the test, its medical implications, the risks and benefits of the test, possible alternatives to the test, and their privacy rights.

Unlike most other medical tests, genetic tests can reveal information not only about the person being tested but also about that person’s relatives. The presence of a harmful genetic mutation in one family member makes it more likely that other blood relatives may also carry the same mutation. Family relationships can be affected when one member of a family discloses genetic test results that may have implications for other family members. Family members may have very different opinions about how useful it is to learn whether they do or do not have a disease-related genetic mutation. Health discussions may get complicated when some family members know their genetic status while other family members do not choose to know their test results. A conversation with genetics professionals may help family members better understand the complicated choices they may face.

Source: NCI (NIH)11

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What is screening?

Screening is looking for cancer before a person has any symptoms. This can help find cancer at an early stage. When abnormal tissue or cancer is found early, it may be easier to treat. By the time symptoms appear, cancer may have begun to spread.

Scientists are trying to better understand which people are more likely to get certain types of cancer. They also study the things we do and the things around us to see if they cause cancer. This information helps doctors recommend who should be screened for cancer, which screening tests should be used, and how often the tests should be done.

It is important to remember that your doctor does not necessarily think you have cancer if he or she suggests a screening test. Screening tests are given when you have no cancer symptoms.

If a screening test result is abnormal, you may need to have more tests done to find out if you have cancer. These are called diagnostic tests.

Source: NCI (NIH)12

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Tests are used to screen for different types of cancer.

Some screening tests are used because they have been shown to be helpful both in finding cancers early and in decreasing the chance of dying from these cancers. Other tests are used because they have been shown to find cancer in some people; however, it has not been proven in clinical trials that use of these tests will decrease the risk of dying from cancer.

Scientists study screening tests to find those with the fewest risks and most benefits. Cancer screening trials also are meant to show whether early detection (finding cancer before it causes symptoms) decreases a person's chance of dying from the disease. For some types of cancer, finding and treating the disease at an early stage may result in a better chance of recovery.

Source: NCI (NIH)13

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Patients who have been treated for cancer need regular screening tests to check for a second cancer.

It is important for patients who have been treated for cancer to be checked for a second cancer before symptoms appear. This is called screening for a second cancer and may help find a second cancer at an early stage. When abnormal tissue or cancer is found early, it may be easier to treat. By the time symptoms appear, cancer may have begun to spread.

It is important to remember that your child's doctor does not necessarily think your child has cancer if he or she suggests a screening test. Screening tests are given when your child has no cancer symptoms. If a screening test result is abnormal, your child may need to have more tests done to find out if he or she has a second cancer. These are called diagnostic tests.

Source: NCI (NIH)14

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The kind of test used to screen for a second cancer depends in part on the kind of cancer treatment the patient had in the past.

All patients who have been treated for cancer should have a physical exam and medical history done once a year. A physical exam of the body is done to check general signs of health, including checking for signs of disease, such as lumps, changes in the skin, or anything else that seems unusual. A medical history is taken to learn about the patient’s health habits and past illnesses and treatments.

If the patient received radiation therapy, the following tests and procedures may be used to check for skin, breast, or colorectal cancer:

  • Skin exam: A doctor or nurse checks the skin for bumps or spots that look abnormal in color, size, shape, or texture, especially in the area where radiation was given. It is suggested that a skin exam be done once a year to check for signs of skin cancer.
  • Breast self-exam : An exam of the breast by the patient. The patient carefully feels the breasts and under the arms for lumps or anything else that seems unusual. It is suggested that women treated with a higher dose of radiation therapy to the chest do a monthly breast self-exam beginning at puberty until age 25 years. Women who were treated with a lower dose of radiation to the chest may not need to begin checking for breast cancer at puberty. Talk to your doctor about when you should begin breast self-exams.
  • Clinical breast exam (CBE): An exam of the breast by a doctor or other health professional. The doctor will carefully feel the breasts and under the arms for lumps or anything else that seems unusual. It is suggested that women treated with a higher dose of radiation therapy to the chest have a clinical breast exam every year beginning at puberty until age 25 years. After age 25 years or 8 years after radiation treatments end (whichever is first), clinical breast exams are done every 6 months. Women who were treated with a lower dose of radiation to the chest may not need to begin checking for breast cancer at puberty. Talk to your doctor about when you should begin clinical breast exams.
  • Mammogram : An x-ray of the breast. A mammogram may be done in women who had a higher dose of radiation to the chest and who do not have dense breasts. It is suggested that these women have a mammogram once a year starting 8 years after treatment or at age 25 years, whichever is later. Talk to your doctor about when you should begin to have mammograms to check for breast cancer.
  • Breast MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of the breast. This procedure is also called nuclear magnetic resonance imaging (NMRI). An MRI may be done in women who had a higher dose of radiation to the chest and who have dense breasts. It is suggested that these women have an MRI once a year starting 8 years after treatment or at age 25 years, whichever is later. If you had radiation to the chest, talk to your doctor about whether you need an MRI of the breast to check for breast cancer.
  • Colonoscopy : A procedure to look inside the rectum and colon for polyps, abnormal areas, or cancer. A colonoscope is inserted through the rectum into the colon. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer. It is suggested that childhood cancer survivors who had a higher dose of radiation to the abdomen, pelvis, or spine have a colonoscopy every 5 years. This begins at age 35 years or 10 years after treatment ended, whichever is later. If you had radiation to the abdomen, pelvis, or spine, talk to your doctor about when you should begin to have a colonoscopies to check for colorectal cancer.

Source: NCI (NIH)15

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Screening tests have risks.

Decisions about screening tests can be difficult. Not all screening tests are helpful and most have risks. Before having any screening test, you may want to discuss the test with your doctor. It is important to know the risks of the test and whether it has been proven to reduce the risk of dying from cancer.

Source: NCI (NIH)16

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While primary prevention aims to reduce the incidence of cancer by tackling the major determinants of cancer, such as smoking, nutrition and physical activity, secondary prevention aims to reduce mortality by early detection of cancer through population screening.

Regular and systematic examinations can detect the disease early, when it is more responsive to less aggressive treatment. Followed by appropriate treatment, these examinations can significantly reduce cancer mortality and improve the quality of life of cancer patients.

Source: EC (EU)17

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screening: Testing or examination of asymptomatic individuals for a specific cancer. The screening process may be indiscriminate, opportunistic (during a routine health check) or systematic (see, population-based cancer screening).

Source: Australian Institute of Health and Welfare18

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Population-based screening is an organised, systematic and integrated process of testing for signs of cancer or pre-cancerous conditions in populations without obvious symptoms. Programs target specific populations and/or age groups where evidence shows screening to be most effective.

Source: Australian Institute of Health and Welfare19

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In Australia, there are national population-based screening programs for breast, cervical and bowel cancers. The programs are run through partnerships between the Australian Government and state and territory governments and aim to reduce illness and death through early detection of cancer or pre-cancerous abnormalities.

Source: Australian Institute of Health and Welfare20

Genetic Tests for Cancer

genetic testing: The process of testing for the presence of particular genetic mutations. This form of testing is available to individuals at increased risk for inherited (familial) cancers, based on a strong family history of those cancers. The breast (and ovarian) cancer genes BRCA1 and BRCA2 are examples of genes with well-characterised mutations that can be "screened’ for in high-risk individuals. The presence of those mutated genes indicates an increased risk of developing breast or ovarian cancers. Similar to other screening tests, individuals receiving a positive test result may be referred for further investigation, or choose to undergo regular tests for pre-cancerous cells.

Source: Australian Institute of Health and Welfare21

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References

  1. Source: NCI (NIH): cancer.gov/ about-cancer/ causes-prevention/ genetics
  2. Source: NCI (NIH): cancer.gov/ about-cancer/ causes-prevention/ genetics/ genetic-testing-fact-sheet
  3. Source: Australian Institute of Health and Welfare: aihw.gov.au/ reports-statistics/ health-conditions-disability-deaths/ cancer/ glossary
  4. ibid.
  5. Source: NHS Choices UK: nhs.uk/ conditions/ Cancer/ 
  6. Source: NCI (NIH): cancer.gov/ about-cancer/ causes-prevention/ genetics/ genetic-testing-fact-sheet
  7. ibid.
  8. ibid.
  9. ibid.
  10. ibid.
  11. ibid.
  12. Source: NCI (NIH): cancer.gov/ types/ bladder/ patient/ bladder-screening-pdq
  13. ibid.
  14. Source: NCI (NIH): cancer.gov/ types/ childhood-cancers/ late-effects-pdq
  15. ibid.
  16. Source: NCI (NIH): cancer.gov/ types/ head-and-neck/ patient/ oral-screening-pdq
  17. Source: EC (EU): ec.europa.eu/ health/ major_chronic_diseases/ diseases/ cancer_en
  18. Source: Australian Institute of Health and Welfare: aihw.gov.au/ reports-statistics/ health-conditions-disability-deaths/ cancer/ glossary
  19. Source: Australian Institute of Health and Welfare: aihw.gov.au/ reports-statistics/ health-welfare-services/ cancer-screening/ overview
  20. Source: Australian Institute of Health and Welfare: aihw.gov.au/ reports-statistics/ health-welfare-services/ cancer-screening/ about
  21. Source: Australian Institute of Health and Welfare: aihw.gov.au/ reports-statistics/ health-conditions-disability-deaths/ cancer/ glossary

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.