Integrated Cancer Care
Panorama Centre For Surgical Oncology
Genetic testing options
What can we test for?
Genetic tests are available for some types of cancer. These include:
- Breast cancer
- Ovarian cancer
- Colon cancer
- Thyroid cancer
- Prostate cancer
- Pancreatic cancer
- Kidney cancer
- Stomach cancer
Genetic testing may help:
- Predict your risk of a particular disease
- Find if you have genes that may pass increased cancer risk to your children
- Provide information to guide your health care
No genetic test can exclude your risk of developing cancer, but it can tell you if you have a higher risk than most people.
Who should have cancer genetic testing?
We follow international and local guidelines about which patients should be referred to a genetic counsellor to assess the appropriateness of genetic testing. These guidelines can be complex, and not all doctors agree on the same approach, but in general the following groups of people are included:
Women who have already been diagnosed with breast cancer:
Most doctors agree that not all women with breast cancer need genetic counselling and testing. This is however highly recommended for women with breast cancer who meet one of the following criteria:
- Diagnosed with breast cancer at a relatively young age (below 50 years)
- You have an unknown family history (adopted or estranged from family) or limited family structure (small family or family members mostly male)
- Triple-negative breast cancer (especially below 60 years of age)
- You have been diagnosed with breast cancer a second time (not a recurrence of the first cancer)
- You have breast cancer in both breasts (bilateral)
- You are of Ashkenazi Jewish and/or Afrikaner descent
- You have a family history of breast (especially at a younger age or in men or 3 or more affected relatives), ovarian, pancreatic, prostate and/or colon cancer
- You have lobular breast cancer and you or one or more family members have diffuse gastric (stomach) cancer
Women who have been diagnosed with ovarian cancer:
International guidelines recommend that all women with ovarian cancer are offered genetic counselling and testing as they may qualify for targeted chemotherapy called PARP-inhibitors (Lynparza), if they are found to carry either a germline (inherited and in all cells of the body) or somatic (in the cancer cells only) BRCA1 or BRCA2 cancer-causing variant. This is especially important in women with ovarian (including fallopian tube and peritoneal) cancer who:
- Are diagnosed with epithelial type of ovarian cancer (especially high grade serous)
- Are of Ashkenazi Jewish and/or Afrikaner descent
- Have a family history of breast (especially at a younger age or in men or 3 or more affected relatives), pancreatic, prostate, ovarian, endometrial (womb) and/or colon cancer.
Individuals who do not have cancer:
Genetic testing is sometimes appropriate for you, even if you yourself have not been diagnosed with cancer. If any of the following scenarios apply to you, you are encouraged to seek advice regarding genetic testing from a genetic counsellor:
- You have a family member who is known to carry a cancer-causing gene variant (for example in the BRCA1 or BRCA2 genes)
- You have a strong family history of cancer: many family members have been diagnosed with cancer, especially if it is the same type of cancer and most of the cancers occurred under the age of 60 years.
- You or one of your parents are adopted and you are concerned about your cancer risks.
Men who have been diagnosed with prostate cancer:
Prostate cancer in men is common and therefore not all men with this type of cancer needs to have genetic counselling and testing. However, if you meet one of the following criteria it is encouraged:
- Diagnosed with prostate cancer at a relatively young age (below 65 years)
- You have high grade (Gleason score more than 7) or intraductal prostate cancer (at any age)
- You have an unknown family history (adopted or estranged from family) or limited family structure (small family)
- You are of Ashkenazi Jewish and/or Afrikaner descent
- You have a family history of prostate (especially more than 2 affected relatives), breast (especially below the age of 50 years or a male relative), ovarian and/or pancreatic cancer.
Individuals who have been diagnosed with colon cancer:
Just as breast cancer, there are many genes known to be associated with the development of colon cancer. Therefore you may want to consider genetic counselling and testing if you meet on or more of to following criteria:
Individuals who have been diagnosed with an endocrine cancer:
If you have been diagnosed with one or more of the following endocrine cancers (growths on secretary glands in the body) and/or meet the following criteria, genetic testing is highly recommended:
- You have medullary thyroid cancer
- You have been diagnosed with more than one endocrine cancer
- You have a pheochromocytoma or paraganglioma
Individuals with other types of cancers:
Genetic counselling and testing is advised in all individuals with the following rare types of cancers:
- exocrine pancreatic cancer
- adrenocortical carcinoma
How are the genetic tests done?
Genetic testing can be done on samples of blood or saliva (spit), or a swab of the inside of a cheek. The laboratory extracts your DNA from these samples and screens your DNA for gene variants associated with a particular disease (cancer).
There are many ways you can have your DNA screened. Testing can be done to look for one specific gene variant or more extensive testing can be done which looks for cancer-causing variants in a number of different genes. Your genetic counsellor (or doctor) will discuss the many options with you and advise you on the most appropriate test for your situation. For example, if the cancer-causing gene variant in your family is known, for instance if your mother is known to carry a cancer-causing BRCA1 gene variant, then testing to only look for this variant will be appropriate. If you are of Afrikaner or Ashkenazi Jewish descent and you have breast cancer, genetic testing will focus on the most common BRCA1 and BRCA2 gene variants known to cause breast cancer within these population groups. If you or your family members have been diagnosed with different types of cancers, and the genetic cause of the cancer in the family is unknown, a more comprehensive gene panel, including many genes associated with the development of cancer, will be recommended.
How do I decide which genetic test is the most appropriate one for me?
Single Gene/ Familial Variant Testing
If the gene variant causing cancer in your family is known, and you are blood-related to the family member who carries the cancer-causing gene variant, genetic testing for this variant only might be appropriate. The cost of single gene or familial variant testing is usually the most cost-effective option as it is very specific. If you would like to undergo this test, you will need to provide your doctor/genetic counsellor with a copy of your family member’s positive genetic test result. In some instances, a blood sample from the family member might also be required.
BRCA1 and BRCA2 Founder Variant Testing
A founder gene variant is a pathogenic (cancer-causing) gene variant that is observed at a high frequency amongst individuals of a particular population group. In South Africa, we have BRCA1 and BRCA2 founder variant testing available for individuals who are of Ashkenazi Jewish, Afrikaner and Xhosa ancestry.
This is a quick test that usually provides a result within a week. It is also the cheapest testing option and most medical aids will cover the cost. However, this is not a comprehensive test as it only looks for a limited number of cancer-causing gene variants in the BRCA1 and BRCA2 genes.
Let’s use the following analogy to explain this better. Let’s say the BRCA1 and BRCA2 genes are instruction manuals that tell your body how to protect you against a specific type of cancer. If there is a spelling mistake in these manuals, your body will not be able to protect you. Genetic testing reads these instruction manuals (your genetic code) to see if it can identify any spelling mistakes (cancer-causing gene variants) which causes you to be less protected against cancer. With the founder variant testing option, the entire instruction manual is not read, instead we only go look on specific pages for mistakes. Therefore, if your founder variant test comes back normal (negative) you may still have a spelling mistake (gene variant) on a different page in the instruction manual.
Comprehensive screening of high-risk genes specific to your cancer diagnosis:
Comprehensive screening entails have a thorough look at a specific gene, meaning the entire instruction manual will be read from page 1 to the last page. This is done through sequencing and MLPA.
This test entails having a thorough look at the specific genes associated with your cancer diagnosis. For breast cancer and colon cancer, there are local gene panels available through PathCare and/or Ampath. These gene panels include between 2 and 9 high-risk genes (BRCA1 and BRCA2 is included for breast cancer). The local gene panels are expensive (about R11 000 to R13 000 depending on the test and your medical aid) and is rarely funded by the medical aid, even with motivation from your doctors. It takes long, about 6 to 8 weeks, to get these results back.
As local testing is expensive, we offer more affordable testing through an USA-based laboratory called Invitae. This laboratory offers many gene panels specific to a particular cancer diagnosis. These gene panels include comprehensive screening of about 20 or more genes. The cost is 250 US Dollars (about R3700 depending on the exchange rate. We do these tests at our practice and charge an additional handling fee of R250 to send the sample to the USA. Local medical aids do not cover the cost of this test. However, the plus side of using the Invitae laboratory, is that family members will be offered free of charge testing if a cancer-causing gene variant is identified.
Extended gene panel testing
The extended gene panel testing is the most comprehensive form of testing as it not only includes the genes associated to a specific type of cancer, but genes associated to all types of inherited cancers. The extended panel testing is only available through the international lab Invitae Laboratories. You can select up to 93 known cancer-associated genes and the cost will still be 250 US Dollars with a R250 handling fee as described above. Once again, local medical aids will not cover the cost of this test. This extended gene panel test is especially recommended if you have a strong family history of several different types of cancer.
We can assist patients world-wide!
See our genetic counsellor for more information
Genetic counseling can help you proactively identify genetic risk factors, based on an expert review of your personal and family health histories. A genetic counselor can help you get appropriate genetic testing and address risks through personalized medical recommendations for you and your doctor to put into action.Click here
Panorama Centre for Surgical Oncology