The Evolution of Genetic and Genomic Testing

As early as the 1950s, scientists developed genetic tests for genetic conditions such as Down syndrome, cystic fibrosis, and Duchenne muscular dystrophy.1 Today, genetic testing can be done before and during pregnancy to determine if genetic disorders are able to be passed on or to determine a condition in utero. With other research, scientists are also able to test how certain medications will be processed in treatment, based on an individual’s genetic makeup.

While genetics looks at the functioning and composition of a single gene, genomics looks at all the genes and their relationships and influence over diseases like cancer. In the Human Genome Project (2003), researchers mapped the human genetic code – anywhere from 20,000 to 30,000 genes in every human cell.

Initially, the technology being developed through blood samples could not differentiate between actual tumor cells and circulating or shedding tumor cells. The circulating tumor DNA (ctDNA) often did not have enough material or nucleotides to be considered an exact match of the patient’s DNA. Biopsies needed to be performed to get a more accurate representation of the tumor type.

While ctDNA can be useful when needing to perform a biopsy in an area difficult to access, or in determining if a tumor is shrinking based on comparative levels, the ctDNA does not provide a complete set of DNA. Scientists had hoped to achieve better results from this “liquid biopsy” of ctDNA, but results have shown a range of significant high false negatives.

The limitations of using the circulating tumor cells for biopsy can be attributed to a very small percentage or undetectable amount of ctDNA in the sample, possibly from a tumor being in the early stages and having fewer cells shedding; or a tumor may have been eradicated but amounts of ctDNA are still in the system.2

As every patient is different, so is every cancer – solidifying the need for a standard of genomic testing on cancer.
 
 
 
 
  1.  https://report.nih.gov/nihfactsheets/ViewFactSheet.aspx?csid=43
  2. https://ghr.nlm.nih.gov/primer/testing/circulatingtumordna