A new testing procedure can identify bowel cancer patients most likely to benefit from a targeted treatment.
Both magnetic resonance imaging (MRI) and a cancer DNA blood test helped doctors predict who would respond best to the drug regorafenib.
The most responsive patients revealed by the scan kept their cancer at bay for 9.4 months longer on average than those whose treatment failed early.
The blood test showed that patients with low circulating tumour DNA levels two months after starting on regorafenib survived an average 9.7 months longer than those experiencing no change or an increase.
Early data indicates that combining the two tests together might be even more promising.
The study, published in the journal Gut, involved 27 patients with chemotherapy-resistant advanced bowel cancer and formed part of a Phase II clinical trial testing regorafenib.
The drug, which restricts blood supply to tumours, is licensed as a last resort treatment for bowel cancer but not currently available on the NHS because of doubts about its effectiveness in unscreened patients.
Study leader Dr Nicola Valeri, from the Institute of Cancer Research, London, said: "We have developed new tests with the potential to detect very quickly which patients are likely to respond long term to the drug regorafenib, and that give an early warning of treatment failure in others who could be switched to another treatment.
"Bowel cancer that has spread around the body is a difficult disease to treat. Although a number of treatments are available they don't always work in the long term, so it's great that it seems we can now pick out patients for whom regorafenib could offer many extra months of life.
"We are now beginning a new trial to make sure that the tests work in a larger group of patients. If our findings are confirmed, we hope policy makers will reconsider the recommendation against use of regorafenib on the NHS for people with bowel cancer.
"We could then use the tests in the clinic to benefit patients who badly need hard and fast answers on whether their treatment will give them precious extra time with their loved ones."