Understanding the Difference Between Genetic vs. Genomic Cancer Screenings
Genetic vs. genomic — the terms are sometimes used interchangeably, but they are not synonymous. Both factor into health and disease. When it comes to cancer screenings, genetic screenings concern risk factors while genomic focuses on the makeup of tumor DNA.
Genetic vs. Genomic
We inherit our genes from our parents. Our genes are responsible for more than our physical appearance. Think of them as the body’s blueprints. They produce proteins enabling the body to function. Every cell in the body contains tens of thousands of genes. A mutation in a single gene can cause out of control cell growth. The result is a tumor.
Genomic is a term that refers to the genome — the study of all your genes. It is another term for the entirety of your DNA. However, the genome should not be confused with the epigenome (also referred to as epigenetics), which, “is a multitude of chemical compounds that can tell the genome what to do. Genomics includes how genes interact with each other and the individual’s environment” as noted by the National Human Genome Research Institute. While people share almost 100% of their genome, there is 0.001% of individual DNA that differs.
Genetic vs. Genomic Cancer Screenings
As the nonprofit Cancer Research Institute notes, cancer is a disease of mutations. Some mutations are inherited — the genetic component — while others are acquired during a person’s lifetime. In fact, the majority of cancers result from acquired mutations while hereditary mutations make up only about 10% of cancers. With cancer screenings, whether a person undergoes genetic vs. genomic testing depends on if there is a family history of cancer or if cancer is already detected.
Genetic Testing
Genetic testing uses blood, saliva or swabs from check cells to determine whether specific gene mutations exist. It is used to ascertain the likelihood of developing a specific type of cancer. If cancer has already been diagnosed, genetic testing reveals whether a gene mutation played a role in the disease.
For example, a woman with a family history of breast cancer may undergo genetic testing to find out whether she has the BRCA1 gene. If she does, her odds of developing breast cancer increase significantly. The good news is that she can opt for a prophylactic mastectomy which reduces the risk of developing breast cancer by up to 95%. The BRCA1 gene also indicates a higher risk of ovarian cancer.
So, the woman may opt to have a prophylactic oophorectomy (a surgery) to remove the ovaries.
Anyone with a family history of certain cancers is generally a candidate for genetic testing. Keep in mind that positive genetic testing results do not mean it is inevitable that the person will develop cancer. Nor does a negative result mean the person won’t develop the disease. It simply means the individual does or does not carry the related gene mutations.
Genomic Testing
Genomic testing looks at cancer genes per se, not heredity. This testing examines changes within the cancer cell. Such changes may occur through behavioral or environmental exposure such as smoking or radiation exposure. However, the cancer cell changes may take place due to random mutations within the cell. Genomic testing is not limited to cancer. Such testing is also performed on normal cells to detect all inherited mutations.
Genomic testing for mutations may reveal how a particular cancer will progress. That ranges from its aggression rate to how likely it is to metastasize (spread). When oncologists know how the cancer is likely to behave, they have a better idea about treatment options. Therapies targeted to attack a mutation cell defect can prevent damage to normal cells.
For cancer patients, genomic testing can determine how gene variations affect medication response. Genomic testing changes over time because the tumor cells continue mutating. Any molecular changes in the tumor can cause resistance to treatment.
Genomic testing is often used for people whose tumors didn’t respond well to radiation, chemotherapy and other standard therapies. It is also used on those whose cancers stopped responding to these treatments. For those with advanced or hard to treat cancers, a more comprehensive type of genomic testing is used. In this testing, a biopsy of the tumor is taken. Cancer cells are isolated, and DNA sequencing takes place. The genetic profile is then scanned for abnormalities. The goal is discovering exactly how the tumor functions. When abnormalities are identified, they are matched to known mutations responsive to other treatments. The person may undergo therapies known to have targeted these mutations.
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Jane Meggitt’s work has appeared in dozens of publications including USA Today, Zack’s, Financial Advisor, nj.com, The Houston Chronicle and The Nest. She is a graduate of New York University.
Sources
Urology Health – Ask the Experts: What is the Difference between Genetic and Genomic Testing?
National Human Genome Research Institute – Epigenomics Fact Sheet
National Human Genome Research Institute – Genetics vs. Genomics Fact Sheet
Cancer Research Institute – Understanding Genomics and Genetic Testing in Cancer Immunotherapy
Komen – The Role of Genetic, Genomic and Tumor Profiling Tests
Mayo Clinic – Preventive (prophylactic) mastectomy: Surgery to reduce breast cancer risk