Genetic testing has become increasingly accessible in recent years. The process is straightforward: submit a sample of blood or saliva, and you can learn about your risk for cancer and other hereditary diseases. But is this testing worth your time? According to John Neary, a licensed genetic counsellor with Hartford HealthCare’s Katherine A. King Rudolph Cancer Genetics Programme, the answer depends on your concerns. If you are worried about cancer risk, genetic testing can assist in customising your medical plan and provide valuable information to your family members.
The focus of genetic testing is to detect harmful variations in the DNA. Our DNA is a unique blueprint, a code made up of four letters—A, T, G, C—representing the human genome. This code acts as a guide for our cells, determining their functions and behaviour. Our genetic makeup, inherited at birth, contains 3.1 billion DNA letters and approximately 22,000 genes. During genetic testing, specialists search for harmful changes or “typos” within this code. As Neary explains, these variations can disrupt the proper functioning of genes. The testing process is akin to spellchecking a person’s genetic code by comparing their DNA sequence to a known baseline.
Two primary forms of genetic testing are used for cancer. Germline analysis is used to identify inherited genetic factors that may increase cancer risk. A notable example is the BRCA1/2 gene, where specific variants can raise the risk of breast cancer. The second form, somatic analysis, examines the genetic makeup of a tumour. This type of testing helps doctors understand the “DNA typos” driving the cancer and can assist in tailoring treatment decisions.
Before diving into genetic testing, it is essential to first understand your family history. Gathering information on who in the family has been diagnosed with cancer, what type of cancer, and the age at diagnosis is crucial for assessing the risk of a cancer predisposition syndrome. According to Neary, having access to your family members’ genetic testing results can also be key. In many instances, doctors can gather medical records from relatives to clarify who in the family might be at risk for a cancer-related genetic factor.
Some types of cancer are more likely to warrant genetic testing. Family history aside, certain cancers should automatically raise the possibility of genetic testing for risk factors. Cancers diagnosed before the age of 50, such as breast or colon cancer, are examples. Others include triple-negative breast cancer, breast cancer in women of Ashkenazi Jewish descent, ovarian cancer, male breast cancer, pancreatic cancer, and metastatic prostate cancer. There are also several rare cancers that fall under this category.
When it comes to managing cancer risk, your doctor is your most important resource. It is important to understand that having a genetic risk factor for cancer does not guarantee a diagnosis. Instead, it increases the likelihood of developing cancer during one’s lifetime. With this knowledge, doctors can help patients manage their risk more effectively. Genetic testing is often the first step in identifying hereditary cancer syndromes. From there, doctors can develop an early action plan which may involve referrals to specialists or genetic counselling. A licensed genetic counsellor can assist in determining if genetic testing is necessary and guide you through the next steps. Together with your doctor, you can create a personalised risk-management plan tailored to your specific needs.
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