What does genetic testing for cancer do?

A genetic test for cancer examines your genes for precise inherited changes (variants). Some of these genetic variants are associated with an increased risk of developing cancer. These inherited variants are responsible for about 5 to 10% of all cancers.

Having a tendency towards cancer makes you a likely probable to acquire this disease. This predisposition is very likely if your parents and/or ancestors have or had cancer.  In other words, a family history of cancer makes you a likely candidate to develop this disease.

Genetic testing for cancer is all about testing to know if you are prone to getting this disease or not. This test will help to find if you have a cancer gene that will mutate a normal cell and make it a cancer cell. This test helps to detect this type of hereditary cancer.

Genetic testing helps you know your probability of developing cancer in your lifetime. It searches for some particular alterations or mutations in your genes, chromosomes, or proteins.

Genetic tests are available to detect genetic mutation in the following types of cancers.

  • Breast cancer
  • Ovarian cancer
  • Colon cancer
  • Thyroid cancer
  • Prostate cancer
  • Pancreatic cancer
  • Melanoma
  • Sarcoma
  • Kidney cancer
  • Stomach cancer

A genetic test can only tell you if you have a higher risk of developing cancer. It cannot say for certain that you will get cancer. What it means is that only some people with a detected gene mutation will develop cancer, not all.

For example, a woman estimated to have a 45% to 65% risk of breast cancer may never develop the disease. However, a woman with a 25% chance may develop breast cancer.

Risk factors for hereditary cancer

Hereditary cancer is cancer caused by an inherited gene mutation. An inherited gene is passed from the parent to the child.

The following factors may increase your risk of developing hereditary cancer and make you a potential candidate to undergo genetic testing:

  • Family history of cancer. Having three or more relatives from the same side of the family with the same types of cancer
  • Cancer at an early age. Having 2 or more relatives who have developed cancer at an early age.
  • Multiple cancers. When one relative develops 2 or more types of cancer.

Cancer can sometimes run in families even if there is no evidence of a gene mutation. Such cancers are not caused by an inherited gene variant but by other risk factors such as environmental factors or adopted lifestyles.

Understanding the genes and cancer link

Understand the normal pattern of the cell as explained below:

  • Each cell contains genes, which are made up of DNA.
  • DNA is a nucleic acid, which is present in the nucleus of almost every cell in our body.
  • It is the DNA that carries our hereditary blueprint or our hereditary characteristics.
  • Each cell is controlled by our genes.
  • It is the genes, which tell the cell how to behave and function. In other words, the cell is under the control of our genes.
  • Genes tell the cell how to function and when to die (cellular suicide or apoptosis).

Now understand this abnormal pattern of the cell:

  • Sometimes the gene tells the cell to behave abnormally.
  • The cell becomes rudimentary and does not perform its normal functions.
  • It does not die when it is supposed to die.
  • The cell goes on multiplying at an abnormally fast and uncontrolled pace. The normal gene has become a cancer gene and the condition is cancer.
  • What has happened is that the gene underwent a change.
  • This changed gene, which you can call a cancer gene, is passed on to the following generations, which makes them prone to cancer.

When should you undergo gene testing for cancer?

Cancer genetic testing is about identifying this cancer gene in a person through a blood test to find out if he is prone to cancer. It is important to note here (before you panic) that not everyone in the following generations with a family history of cancer carries this faulty gene.

Genetic counseling will help you decide if you should undergo or if you are the right candidate for this cancer screening test. For information’s sake, let us see what can make you a potential candidate for gene testing for cancer.

You should screen yourself for cancer through genetic testing if you have two or more close relatives who have or had cancer – more importantly before the age of 50 years. When we say close relatives, we mean

  • Father
  • Mother
  • Brother
  • Sister
  • Grandparents on mother’s as well as father’s side
  • Father’s brother or sister
  • Mother’s brother or sister


BRCA1 and BRCA2 are a type of genes that give stability to the DNA in the cell and prevent mutation and uncontrolled growth of the cells. They are, therefore called tumor suppressors. When these genes undergo mutation, or when they become cancer genes, there is the development of breast cancer and ovarian cancer. The “BRCA” stands for breast cancer.

In women, besides the risk of breast and ovarian cancer at an early age, mutation of these genes increases the risk of uterine, cervical, colon, and pancreatic cancer.

In men, mutation of BRCA1 and BRCA2 genes increases the risk of breast cancer, testicular, prostate, and pancreatic cancer.

How is cancer genetic testing done?

Genetic testing for cancer may be done on a sample of blood, hair, buccal smear, (smear taken from the inside of the cheeks), urine, amniotic fluid (the fluid that surrounds a fetus during pregnancy), or other body tissues.

It is first done on a family member diagnosed with cancer. If the result of cancer tests is positive, other family members are asked to undergo genetic screening.

Drawbacks or limitations of cancer genetic test

  • It is an expensive test. The cost of genetic testing for cancer can vary greatly and can be between $300 and $5,000.
  • The results of genetic testing take weeks to come.
  • A negative test does not rule you out of getting cancer.
  • If the test result is negative, there is still a 20% chance of getting cancer.
  • If the test is positive, it only indicates that you are at a greater risk of getting cancer. In other words, even if the test is positive, you may still not get cancer.
  • Even if the mutation is present, it may go undetected.
  • Even if the mutation is detected, there is no preventive treatment for the genetic disorder.
  • Emotional stress develops in the member and family if he tests positive.

Benefits of genetic testing for cancer

  • The mental state of uncertainty is reduced.
  • Gene testing for cancer gives an idea of cancer risk to the patient and family members.
  • Makes you improve your lifestyle habits and take preventive measures, thereby reducing your exposure to risk factors that can make you prone to cancer.
  • A positive test makes you eligible for periodic cancer screening and early cancer detection before the cancer spreads. This always increases the chances of a good prognosis.