DNA blood test could track early breast cancer

A new blood test could be up to 100 times more sensitive at monitoring the progress of early stage breast cancer than existing tests, scientists believe.

A consultant analyses a mammogram. Picture: Rui Vieira/PA Wire

The targeted digital sequencing (TARDIS) test analyses tiny fragments of tumour DNA in the bloodstream and doctors hope they will be able to use it to track the effectiveness of early treatments.

It can detect “extremely low concentrations” of cancer DNA at an earlier stage than existing blood tests, according to Dr Muhammed Murtaza, from the Translational Genomics Research Institute (TGen) in Arizona, where the test was developed.

It could also prevent women from having unnecessary surgery to remove tumour residue after chemotherapy, with lower concentrations in the blood suggesting that treatment has already been successful.

Breast cancer is the UK’s most common cancer, with around 55,000 women and 350 men being diagnosed each year.

Professor Carlos Caldas, director of the Breast Cancer Programme at the Cancer Research UK Cambridge Centre, which contributed to the study, said: “This could be a game-changer.

“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.”

The research is published in the Science Translational Medicine journal.

People with early-stage breast cancer can be treated with chemotherapy to shrink their tumour before having surgery to remove any remaining cancer.

But experts say that no cancer cells are found in almost a third (30 per cent) of those who go under the knife after treatment.

The researchers hope it could be used to monitor the progression of other cancers that are treated with drugs before surgery.

The test is more accurate than others because it looks for DNA sequences specific to each patient’s cancer, the researchers say.

A biopsy of the cancer is taken, its DNA sequenced and scientists then look for mutations common across all cancer cells.

The researchers analysed 80 blood samples from 33 women with early stage and locally advanced breast cancer.

They found that the concentration of tumour DNA in the bloodstream of patients who had no breast cancer cells remaining at the point of surgery was lower than in those that did.

They will now carry out a study on more than 200 patients to further analyse what the test can show.

Prof Caldas added: “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.”