Genomic Medicine

- Overview

Genomic medicine is an emerging medical discipline that involves the use of an individual's genomic information as part of their clinical care (eg, for diagnosis or treatment decisions) and the health outcomes and policy implications of that clinical use. 

Genomic medicine has already made an impact in the fields of oncology, pharmacology, rare and undiagnosed diseases, and infectious diseases. 

- Genomic Cancer Tests

To get a tissue sample from your cancer, your doctor will perform a biopsy. It is already a standard part that doctors use to diagnose cancer. Genomic testing is a relatively new process that allows tumors to be tested for mutations that drive cancer growth. This is very helpful in determining treatment.

Genomic testing looks at the genes in your cancer to help your doctor make more informed decisions about your disease and match you with the right treatment. These tests are also useful if your cancer has not responded to the treatment you have been receiving, or if it has come back. 

The type of genomic test your doctor does is different from the DNA tests you can buy online through companies like Ancestry or 23andMe. These consumer-based tests give you an idea of your genetic profile and how your DNA may affect your health. They cannot help your doctor diagnose or treat your cancer. A genomic test ordered by your doctor provides specific information about your cancer cells and the best way to treat your cancer. 

To perform a genomic test, your doctor will first need a blood or tissue sample from your cancer. The sample will be sent to a laboratory, which will test it for certain genetic changes that affect how the cancer grows and how it responds to treatment.

- Gene Sequencing

The next step in the process is to sequence the cancer's DNA. Your DNA is a long code made up of four units, called bases: 

• Adenine (A)
• Cytosine (C)
• Guanine (G)
• Thymine (T)

Each is paired - A with T and C with G. The sequence or sequence of these pairs contains the code or instructions for making the proteins your body needs to function. DNA sequencing tests look at the order of these pairs to find normal changes that help cancer grow. 

Because your genome contains about 3 billion base pairs, sequencing typically takes a long time. A new high-tech method called next-generation sequencing scans multiple strands of DNA at once to speed up the process and get results to you and your doctor faster. 

Genome sequencing can be done in different ways. Whole-exome sequencing looks at the portion of the genome that codes for proteins. Whole genome sequencing looks at all the DNA in your cancer. 

Another test counts the number of times certain genetic mutations occur in your cancer, which is called tumor mutational burden. This test can help your doctor predict whether a group of drugs called immune checkpoint inhibitors will work against your cancer.

[More to come ...]