Blood tests could replace needle biopsies

The Álvaro Cunqueiro Hospital in Vigo, Pontevedra province, has launched clinical trials to see whether the so-called 'liquid biopsy' method would be accurate enough to replace the traditional process.

If it is, this means patients would have their results within a maximum of two hours, rather than having to wait for a minimum of two days, as is the case with the current method.

Were a blood test to suffice, a biopsy on a suspect lump or cell cluster – a common way of testing for cancer – could be carried out at an outpatient's nurses' station, saving resources, since at present, biopsies are conducted by surgeons or interventional radiologists.

Sample cells are taken with a needle, which means the process can be painful for the patient – especially where the process is extremely invasive, such as in an internal organ or collecting bone-marrow cells.

The cells taken are then normally examined under microscope by a pathologist, or can be analysed chemically.

'Liquid biopsies' come in two types – the circulating tumour cell assay, or cell-free circulating tumour DNA tests.

This procedure is more likely to gain a picture of the full genetic makeup of a tumour – needle biopsies may miss some features of the tumour's DNA and are not always effective in attempting to understand how cancerous cells are progressing.

Additionally, excisional biopsies – where the entire lesion or tumour is removed for analysis – and incisional biopsies, where a needle is used to take a sample, cannot be repeated over time to monitor tumour growth or ongoing genetic mutations.

Cell-free circulating tumour DNA liquid biopsies are the most thorough, given that around 100 times more cell-free DNA exists than DNA in circulating tumour cells, so the test can allow for fragments of DNA from tumour cells constantly being shed into the bloodstream to be examined.

Three years ago, an experiment involving taking blood from 846 patients with 15 types of cancer in 24 hospitals enabled medics to detect cancerous DNA in the blood of over 80% of those with metastasis and 47% of those with localised tumours, although the blood samples were not able to pinpoint where the tumours were located.

However, no false positive results were found.

If the hospital in Vigo is in fact able to replace traditional biopsies with 'liquid' methods, the system will be much faster, painless and cheaper as well as requiring fewer resources, the research team says.

Photograph: Wikimedia Commons