A NEW liquid biopsy blood test that could revolutionise the way doctors monitor and tackle the spread of cancer is being developed by scientists. The test is sensitive enough to detect a stray cancer cell among a billion blood cells, which would indicate that an existing tumour has spread elsewhere in the body or is likely to. It also shows if the level of blood-borne cancer cells falls in response to treatment, giving doctors a clearer gauge of success, and analyses the cells biological makeup to inform predictions of their next move. The test could replace the painful tissue sampling currently used to monitor the growth of tumours, and could eventually be used instead of procedures like mammograms or colonoscopies to screen for new cancers. Four large cancer hospitals across the US will begin testing the procedure this year. They will use the test to discover more promptly whether their treatments of patients existing cancers are proving effective. Dr Daniel Haber, one of the tests inventors, said: If you could find out quickly, 'this drug is working, stay on it, or 'this drug is not working, try something else, that would be huge. The needle biopsies through which many cancers are diagnosed generally do not provide enough of a sample to tell doctors how the tumour is likely to grow. To measure the size of the cancer, patients are typically given a CT scan months after receiving drug or radiation treatment. But the time lag often means they die before an effective treatment plan is found. It is hoped that the new blood test would enable doctors to measure the success of treatments far sooner, meaning more options could be tried during a patients make-or-break months. Dr Haber said doctors could deliver a treatment one day and sample the patients blood the next in order to see if circulating tumour cells had gone. The test features a microchip covered in almost 80,000 tiny bristles. These are coated with antibodies that trap cancer cells when blood is pumped around the chip. Researchers then apply a stain to the bristles, which makes the cancer cells glow, allowing them to count them and capture them for analysis. Telegraph