Over the past few years, you may have heard about genetic or genomic testing for cancer but you may be confused as to when you should consider doing a genomic test and how it might actually help you in your health journey. The answer depends on the question you may have. Let's consider the following scenarios :
1. You are aware that there is a history of cancer in the family and you want to know if you have genes that predispose you to cancer
In this case, you would typically do a polygenic risk score-based test like Oncomap or Genomepatri that helps you understand risk but also the factors that can help you mitigate risk through lifestyle. These tests help predict your risk for cancer and thus motivate you to make lifestyle changes and to take regular screening tests so you can diagnose cancer early. Just to help you with statistics, 50% of cancers are preventable and most cancers are treatable if caught early. For example in India, Colorectal Cancer has a vast difference in recovery rates based on the stage of cancer- ranging from 97.7% to 43.9% at stages 1 and 4 respectively. Lung Cancer to has the same pattern, with one-year survival at 87.3% for stage 1 and 18.7% for stage 4. The sample you provide in this case could be saliva or blood.
2. Someone in your family or friend circle has already gotten cancer.
The doctor wants to find a treatment that would best work for them. Let's say colorectal cancer. In this case, you would use what we call tumour DNA sequencing. Basically, the DNA in these tumour cells have changes that show cancer. This is called somatic mutation testing. This analysis would typically be used to understand what treatment would best work for you. The sample in this case would be tissue from the site of cancer.
3. Someone in your family recently had cancer and you want to understand if you have the same mutation.
In this case, typically they would test the person who got cancer first, find the mutations causing it and then the rest of the family members would be tested for the same mutation to see if they have inherited the mutation. In this case, the test recommended would be a combination of Next Generation Sequencing(NGS) and Sanger Sequencing to test for the immediate family or NGS for all members.
4. You read about Angelina Jolie decided to go through double mastectomy as a preventative measure.
You speak to your doctor and based on your family history want to understand if there is a risk that you may have and if surgery is an option for you. The sample would be blood or saliva and it would be a Sequencing based test.
5. Cancer was diagnosed at an unusually young age typically below the age of 50.
This alarms the family members and they want to test for mutations that predispose them to cancer.
6. Too many types of cancer were diagnosed in the same patient causing panic in the family.
This could mean that there is a pathogenic/harmful mutation and you want to identify it.
7. Birth defects
Birth defects that are known to be associated with inherited cancer syndromes that show up as skin growths and skeletal abnormalities.
In all of the above cases, Genetic Counselling is generally recommended before any test is ordered and after the test report is given so that the patient/ customer is aware of what the testing may reveal and to help interpret results. This counselling should be performed by a trained genetic counsellor or other health care professional who is experienced in cancer genetics. If a test is ordered in the presence of an oncologist when a patient is already diagnosed it is typically used to design the course of treatment.