Scientists at the Institute of Cancer Research in London have developed a new blood test that could save countless lives. According to a report from the BBC, trials showed that the test was effective at detecting breast cancer relapses in 12 out of 15 women.

The secret to the test lies in the wonders of DNA. When people have tumors surgically removed, the cancerous growths often leave behind traces of their own genetic information. While experts believe that the test will probably not be ready for widespread use for a couple more years, many are confident in the new test’s ability to locate these miniscule traces of cancer, months before they grow into something more serious again.

The study examined 55 patients who were at a high risk for cancer relapse after having large tumors removed with surgery. Researchers examined the mutated DNA from tumor cells and then scanned blood samples for traces that matched. Of the 55 patients, 15 of them relapsed and developed subsequent tumors. The blood test was able to give 12 out of these 15 an advanced warning.

The other three patients had cancerous cells in their brains, where a protective blood-brain barrier may have trapped cancerous DNA from circulating throughout the body.

The blood work is relatively cheap, but scanning for DNA mutations remains expensive. The test is much less invasive and faster than traditional cancer screens, but it will still be some time before the test is fully developed and ready for use.