Code and the crab

Genomic testing is reshaping the way we find and treat cancer

- Priya Menon

In cancer, diagnoses are done largely by looking through the microscope at the appearance of cancer cells and, often, the organ the cancer comes from offers the most important way of making the diagnosis. But, over the past couple of decades, doctors and researchers have realised that a much better way to diagnose cancer is by the molecular abnormalities that distinguish cancer cells from normal ones; these abnormalities are often changes in the DNA sequence in the genome of the cancer cells.

Cancer is a disease of the genome. Each cell within our body contains all of the genetic code required for human life and development. This genetic code is composed of over three billion DNA molecules, joined together into 46 long strings known as chromosomes. Collectively, the DNA that makes up all 46 chromosomes is known as the genome. Every time a cell divides, it makes two copies of its DNA that are passed on to its daughter cells. But, occasionally, errors are made while copying the DNA, resulting in mutations in the daughter cells. The great majority of mutations are harmless, but some can develop into a tumour.

Cancer genomics is the study of these mutations. For example, 12 years ago lung cancer was classified as either small cell or nonsmall cell. Today, it is identified by nearly 30 genomic mutations or changes. Identifying specific mutations in patients marks a radical shift from a one-sizefits-all treatment towards more personalised therapy.

Precision medicine

Precision medicine’s central principle centres on the ability to identify personal gene characteristics and match them to specific treatment options. It is an emerging approach in cancer treatment and prevention.