The test in question is one of the first to successfully monitor breast cancer patients with early stage disease, and could be up to 100 times more sensitive than existing tests, according to a study published in Science Translational Medicine.

Researchers at the Translational Genomics Research Institute and the Mayo Clinic in Arizona, in collaboration with scientists at the Cancer Research UK Cambridge Institute, have developed the new method for tracking breast cancer that could one day hopefully help doctors better tailor treatments and prevent unnecessary surgeries for some people with the disease.

TARDIS (TARgeted DIgitial Sequencing)  – the technique – works by analysing the circulating tumour DNA, or tiny fragments of DNA from cancer cells in the bloodstream. This means that the test could one day allow doctors to use blood samples to continuously monitor how well breast cancer treatments are working – allowing them to personalise each patient’s treatment plan.

In a first validation study the researchers analysed 80 blood samples from 33 women with early stage and locally advanced breast cancer, and found that the test was able to identify circulating tumour DNA in every patient before they started treatment.

Because of this, researchers did further blood tests on the 22 women who received treatment before their surgery, such as chemotherapy, radiotherapy or hormone therapy. The test found that the concentration of circulating tumour DNA was lower for those patients that had no breast cancer cells remaining at the point of surgery, than for those that did.

Dr Muhammed Murtaza, lead author of the study and co-director of TGen’s Center for Noninvasive Diagnostics, where the test was developed, said that until now, blood tests for breast cancer have “only been sensitive enough to reliably identify tumour DNA in people with advanced disease.”

He went on to explain that the organisation has “shown that TARDIS is able to detect circulating DNA at extremely low concentrations in the blood, opening up the possibility of monitoring patients with early-stage breast cancer to find out how their disease is responding to treatment.”

TARDIS is more precise than other cancer blood tests as it looks for DNA sequences specific to each patient’s cancer. The test relies on a traditional biopsy of the tumour being taken first – where a sample of the tumour is removed with a needle. The tumour DNA is then sequenced, and bioinformatics is used to identify mutations likely to be present in all cancer cells.

The vast majority (around 95%) of breast cancer cases are diagnosed at an early or locally advanced stage (stages I-III), out of those with a known stage at diagnosis in the UK.