Blood test could improve breast cancer detection and monitoring

UK and US researchers have developed a highly sensitive blood test that can be used to monitor breast cancer patients with early-stage disease, and could one day help doctors to continuously check how well breast cancer treatments are working.

Many people with early-stage breast cancer are treated with drugs to shrink the tumour, followed by surgery to remove any remaining cancer. However, for around 30% of these patients, no breast cancer cells are found when they go under the knife, as the earlier treatments were completely effective. Currently, doctors have no way of knowing which women could avoid this unnecessary, invasive procedure.

Researchers at the Translational Genomics Research Institute (TGen) and the Mayo Clinic in Arizona, in collaboration with scientists at the Cancer Research UK Cambridge Institute, have now developed a method for tracking breast cancer that could one day help doctors better tailor treatments and prevent unnecessary surgeries. Their work has been published in the journal Science Translational Medicine.

Called TARDIS (TARgeted DIgitial Sequencing), the technique is more precise than other cancer blood tests as it looks for DNA sequences specific to each patient’s cancer. A traditional biopsy of the tumour is taken first, the tumour DNA is sequenced and bioinformatics is used to identify mutations likely to be present in all cancer cells. The method is said to be up to 100 times more sensitive than existing tests and could one day allow doctors to continuously monitor how well breast cancer treatments are working.

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

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

The 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 who had no breast cancer cells remaining at the point of surgery than for those who did.

The researchers will now carry out a larger study, involving over 200 patients, to further validate the effectiveness of the test, and to determine the concentration of circulating DNA in the blood that could indicate to doctors that treatment prior to surgery has been successful. This could lead to clinical trials to find out whether the test can be used to reliably inform treatment decisions in a real-world setting.

“This could be a game changer,” said study co-author Professor Carlos Caldas, Director of the Breast Cancer Programme at the Cancer Research UK Cambridge Institute. “Instead of patients undergoing six to eight cycles of chemotherapy (15–21 weeks of treatment), after one or two cycles (3–6 weeks) we would use the TARDIS test to look for a significant drop in circulating tumour DNA. If a drop was not detected, the treatment could be stopped or changed.

“Finding cancer DNA in the blood is like looking for a needle in a haystack. But by developing a test that’s unique to each patient, and looking for mutations present across the entire tumour, we’ve made it much harder for the circulating tumour DNA to hide, significantly increasing the chance of identifying cancer relapses earlier.”

Professor Karen Vousden, Cancer Research UK’s Chief Scientist, added: “Our understanding of what drives individual patients’ cancers has opened up numerous opportunities for more personalised treatments for people with breast cancer. Although still in its early stages, this innovative new technology has the potential to increase the number of people who can benefit.

“A blood test that indicates whether a therapy has been effective could prevent some patients from undergoing further unnecessary treatments, transforming patient care.”

Image credit: ©stock.adobe.com/au/Africa Studio

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