Blood test for cancer screening

The new circulating tumour DNA test (ctDNA)

Diagnostic technology for the early detection of cancer has taken another massive leap forward with the commercial release of new, relatively simple blood tests. These tests that detect tumour DNA as it arises will increasingly become a routine part of all health screens and will replace the need for other invasive tests such as smears and tissue biopsies. However, genetic testing is set to become even less invasive as ctDNA has also been detected in other bodily fluids, including urine and saliva. Other less expensive tests such as Progastrin, for detecting multiple gastro-intestinal, gynaecological and skin cancers are also becoming increasingly available.

In addition, as part of the whole new approach to 'precision medicine' the new circulating tumour DNA test is already being developed further with more tumour-specific marker tests, that can identify the type of cancer, which informs where the cancer originates from.

All the cells in our bodies are in a constant cycle of birth, growth and death and so the test is made possible because dying cancer / tumour cells release their DNA into the bloodstream. These bits of genetic material are called cell-free circulating tumour DNA (ctDNA). The point is that these bits of DNA are mutated and therefore different to the normal, healthy DNA and it is this difference in genetic sequence that the test can detect. Further information on this test can be found on the Genetic Home Reference site.

Clinical and diagnostic relevance

There is still a lot of work to ascertain the true value of these tests as clinically valuable screening tools as all the usual caveats over the performance of diagnostic tests exist. Much work is currently being undertaken. Sensitivity (how early something can be detected), specificity (accuracy) and clinical relevance have to be further investigated. The type and origin of the cancer will affect ctDNA levels, and other variables include the following factors:

  • previous treatments
  • demographic, and
  • environmental factors
  • Sometimes mutations may appear in different parts of the material (making detection more difficult
  • Rates at which ctDNA is cleared from the system

However, this is the natural evolution and proper scientific way for evaluating the use of all new diagnostic tests. It is envisaged that this highly practicable method is the future of onco-diagnostics. In addition, the tests will become useful markers (known as surrogate markers) for monitoring the success of treatments.

Leading Clinical Oncologist, Dr Andy Gaya tells Total Health that the way in which cancer is now detected and treated will be completely revolutionised by the release of these new screening tests combined with a host of new treatments including Proton Therapy, biological and other targeted therapies.



A fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. 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 building blocks of the genes in almost all living organisms - spelt out in full as deoxyribonucleic acid. Full medical glossary
A viral infection affecting the respiratory system. 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 animal or plant that supports a parasite. Full medical glossary
relating to the intestines, the digestive tract between the stomach and the anus 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
A way to identify people who may have a certain condition, among a group of people who may or may not seem to Full medical glossary
A group of cells with a similar structure and a specialised function. Full medical glossary
An abnormal swelling. Full medical glossary
Liable to vary or change. Full medical glossary