What Genomic Testing Can Tell You About Health Risks

Genomic testing looks at the ways in which your genes interact and what those interactions mean to your health. Genomic testing is different from genetic testing because it looks at all of your genes, rather than detecting a single gene mutation.

Genomic testing can show how your body works on a molecular level and what that means for disease risk, progression, or recurrence.

Genomic testing is commonly used in cancer treatment to determine how a tumor will likely behave. This can help healthcare providers predict how aggressive your cancer will be and whether it is likely to spread (metastasize) to other parts of the body.

Genetics vs. Genomics

Genetics and genomics are both associated with genes, but tests have entirely different aims and applications.

Genetics

Genetics is the study of the effects that genes have on an individual.

Genes provide the body instructions on how to make proteins. Proteins determine the structure and function of each cell of the body.

Genes are made up of building blocks called DNA that are arranged in a string called bases. The order, or sequencing, of bases will determine which instructions are sent and when.

Many genes are coded to make specific proteins. Non-coded genes regulate how and when the proteins are made by turning on and off certain genes. Any deviation in how a gene works may influence the risk of certain diseases, depending on which proteins are affected.

In some cases, a single gene mutation can lead to conditions such as cystic fibrosis, muscular dystrophy, and sickle cell disease. The BRCA1 and BRCA2 mutations are associated with breast and ovarian cancer.

Genomics

Genomics is the study of the structure, function, mapping, and evolution of the complete set of DNA, including all of the genes.

The genetic material plus all of sequences are called the genome. Genomics aims to analyze the function and structure of a genome to:

• Understand how complex biological systems (like the the cardiovascular system and endocrine system) influence each other
• Predict what problems can happen if genetic interactions interfere with normal biological functions

There are between 20,000 to 25,000 different protein-coding genes and about 2,000 non-coded regulatory genes in the human genome.

Genomics is important because it helps show why some people are genetically predisposed to certain illnesses, even if the way certain genes interact is unknown.

Rather than identifying a single genetic pathway, genomics evaluates the multitude of genetic variables that affect the development or treatment of a disease (such as cancer or diabetes).

By understanding these ever-changing variables, healthcare providers can make more informed choices in treatment—often preemptively.

What Genomic Testing Is Used For

Genomic testing is based on current understanding of the human genome. This process began with the collaborative Human Genome Project from 1990 to 2003.

Scientists have been able to increasingly identify which genetic anomalies translate to the development and characteristics of a disease. This information explains why some people develop more aggressive forms of cancer, live longer with HIV, or don't respond to certain forms of chemotherapy.

Genetic tests can confirm or rule out a suspected genetic condition. Genomic testing takes it one step further by providing:

• Risk markers to screen for diseases
• Prognostic markers to predict how fast a disease will progress, how likely it is to recur, and the likely outcome of a disease
• Predictive markers to guide treatment choices and avoid toxicity
• Response markers to determine the efficacy of various treatments

While genomics focuses on the implications of our genetic makeup irrespective of all other factors, it is not used in isolation.

The growing movement toward personalized medicine is changing how we approach diseases in general. Rather than a one-size-fits-all solution, personalized medicine takes into account the high variability in genetics, environment, and lifestyle to offer a more tailor-made solution for each individual.

How Genomic Testing Works

Genomic testing is typically offered as a panel of targeted genes, ranging from an analysis of genetic "hot spots" (well-established sites of mutation) to full gene sequencing.

The tests are typically performed in a specialized lab certified under the Clinical Laboratory Improvement Amendments (CLIA). There are more over 500 CLIA-certified genetics labs in the United States.

Once the sample is obtained, it usually takes between one and four weeks to receive the results.

Depending on the condition being treated, a genetic counselor may be on hand to help you understand the limitations of the test and what the results mean and don't mean.

Next-Generation Sequencing

Next-generation sequencing is the primary tool for genomic testing.

It identifies and evaluates the genetic sequence of millions of short DNA segments called reads. The reads are then assembled into a complete sequence to determine which genetic variations (variants) are present and what they mean.

Next-generation sequencing is extremely flexible and can be used to sequence only a few genes, such as for a hereditary breast cancer panel, or the whole genome used typically for research purposes to screen for rare diseases.

Since most variants have little or no known impact on human health, they will be filtered out to identify the few that are medically meaningful. These variants will then be scored on a five-point scale ranging from:

1. Benign (not disease-causing)
2. Likely benign
3. Uncertain
4. Likely pathogenic (disease-causing)
5. Pathogenic

While most labs will report the pathogenic and likely pathogenic findings, some will also include the uncertain, likely benign, and benign findings as well. An interpretation from a certified geneticist would also be included.

Primary and Secondary Results

Results directly related to a suspected condition are referred to primary results, while those that are medically meaningful but unrelated are called secondary (or incidental) results.

Secondary findings are often relevant and may reveal a person’s genetic risk of a future disease, carrier status, or pharmacogenetic findings (how your body processes a specific drug). In some cases, testing may also be performed on your parents to help identify which variants are shared and which are de novo (not inherited).

Genomic Testing in Cancer

Genomic testing has become an integral part of treating and managing different types of cancer, including breast cancer and lung cancer.

Genetic tests may help identify a person’s risk of cancer, but genomic testing helps identify the genetic markers associated with the characteristic of the disease.

Genomic tests can help predict:

• The behavior of a tumor
• How fast a tumor will grow
• How likely a tumor will metastasize

This is important because the cells of a tumor can mutate rapidly. Even if a single genetic variant is responsible for a tumor, the disease itself can take many different courses, some aggressive and others not.

While a genetic test may help identify the malignancy, a genomic test can identify the most effective ways to treat it.

If a tumor suddenly mutates, a genomic test can spot if the mutation is receptive to targeted therapy. One example is the drug Nerlynx (neratinib) used to target and treat early-stage HER2-positive breast cancer.

Genomic vs. Genetic Testing in Breast Cancer

Home Genomic Testing

Home genomic testing is widely available.

Some home genetic tests are designed solely to trace a person’s ancestry, like the AncestryDNA and National Geographic Geno 2.0 tests.

23andMe offer consumers the chance to identify their risk of certain genetic health disorders and predisposition to the following conditions:

• Alpha-1 antitrypsin deficiency (a genetic disorder linked to lung and liver disease)
• Celiac disease
• Early-onset primary dystonia (an involuntary movement disorder)
• Factor XI deficiency (a blood clotting disorder)
• Gaucher disease type 1
• Glucose-6-phosphate dehydrogenase deficiency (a red blood cell disorder)
• Hereditary hemochromatosis (an iron overload disorder)
• Hereditary thrombophilia (a blood clotting disorder)
• Late-onset Alzheimer’s disease
• Parkinson’s disease