Genetic testing and biomarkers for Cancer

Finding new and significant biomarkers in a patient's DNA is being widely reported as the future of diagnostic-led medicine. The theory is that by knowing a patient's genome, finding the presence of mutations and knowing how these mutations affect the effectiveness of different treatment options means that every patient will potentially be able to receive personalised treatment regimes.DNA sequencing

This approach to personalised medicine is increasingly becoming routine. For example breast cancer patients are now offered testing for the presence of BRCA gene mutations. This is because it is known that different drugs such as Herceptin have different outcome profiles depending on the presence of these mutations. Mutations, or changes in the gene sequencing within the DNA can occur spontaneously. The result of a mutation is that the cell will produce a different type of protein from normal - and it is these proteins that may have an important role in the subsequent development of tumours, or be a target for drug therapy. There are now over fifty approved drugs that mention the possibility to test for the presence of relevant biomarkers on their labels.

Why test for RAS Biomarkers?

An important set of genes that are involved in whether or not a cell grows and divides are called RAS genes.and these produce the RAS proteins, which act as an on / off switch. It has been shown that mutated RAS proteins can be responsible for affecting the on / off switch and therefore helping tumours to develop. The presence of this gene is particularly important for patients with cancer of the colon as some drugs are not effective in tumours that carry the RAS gene. Genetic testing for the presence of the RAS biomarkers in patients with metastatic colorectal cancer is therefore significant.and this is now increasingly provided routinely from specialist test centres such as the Haematology Department at Hammersmith Hospital and other molecular profiling laboratories.

There are now hundreds of different genetic tests and many more are being developed. However, it is one thing to discover a new genetic mutation, but quite another to ascertain the medical significance. The question for most tests still remains, "so what?". It is also important to differentiate the types of application. For example, some markers may be useful for diagnosing inherited disorders, whereas others will be used to inform treatment effectiveness, or what is termed 'pharmacogenomics'.

It is still relatively early days and a huge amount of work still has to be done in order to answer the 'so what?' question. However, rapid advances in research, The need for interpreting the results from genetic testing is becoming a highly important science in its own right.

Another factor is that the tests themselves are subject to human error and subjective interpretation. One company leading the way in this field, Sophia Genetics, say, "One of the biggest problems with understanding the significance of genetic testing is that there are a number of human decisions that are required with existing approaches to analyzing and interpreting genetic information. While this may be acceptable in a research setting where new discoveries are being made, it is not ideal in a clinical diagnostic environment where Clinicians and Oncologists are striving for the highest degrees of repeatability and accuracy."

Sophia Genetics therefore place emphasis on machine learning and what they call, "Iterative Bayes decision making that builds an unbiased view of the data — not using a specific training set or time period."

Regardless of the scientific hurdles and complexities around interpretation and application, the rapid advances in genes biology means that there will be an explosion of new biomarker tests. While patients will want to receive the benefits, it will be critical to ensure that there are proper safeguards to ensure the appropriate transition of these tests from the research labs to routine pathology testing.

A substance that can be measured to help healthcare professionals to assess normal processes, disease processes or a person's response to treatment. Full medical glossary
Abnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. Full medical glossary
The basic unit of all living organisms. Full medical glossary
The large intestine. Full medical glossary
The specialisation of cells or tissues for a specific function. Full medical glossary
The building blocks of the genes in almost all living organisms - spelt out in full as deoxyribonucleic acid. Full medical glossary
The basic unit of genetic material carried on chromosomes. Full medical glossary
Relating to the genes, the basic units of genetic material. Full medical glossary
An element present in haemoglobin in the red cells. Full medical glossary
A change in the genetic material (DNA) of a cell, or the change this this causes in a characteristic of the individual, which is not caused by normal genetic processes. Full medical glossary
Compounds that form the structure of muscles and other tissues in the body, as well as comprising enzymes and hormones. Full medical glossary
rheumatoid arthritis Full medical glossary
Relating to the rectum, the lowest part of the bowel leading to the anus. Full medical glossary
An abnormal swelling. Full medical glossary