For patients whose cancer has spread beyond the breast and nearby glands – the most deadly stage of the disease – the new test could be used to improve and individualize their treatment as the disease progresses, researchers have said.

Around 10 percent of women have metastatic, or stage four, breast cancer at the time of their diagnosis, according to cancer support charity Macmillan. The average survival rate is around two years.

This is the first time scientists have been able to analyze two kinds of acquired DNA mutation in a single blood test. In addition, the test can spot mutations in the estrogen receptor gene ESR1, linked to resistance to anti-hormone therapies such as aromatase inhibitors.

“This study represents proof of concept, and further validation is now needed to confirm the clinical usefulness of this test before any test could be rolled out…The researchers may have developed a way to track breast cancer as it grows, allowing doctors to act swiftly and give patients the treatments that are right for them as early as possible. On top of that, such a tailored approach could spare patients receiving drugs, and the side effects that go with them, that aren’t likely to work.”