U.S. researchers said Monday they have developed a new blood test that has the potential to detect cancers in their earliest stages.

In a proof-of-principle study, researchers from Stanford University administered a drug called DNA minicircles to mice and found mice with tumors produced a substance that tumor-free mice didn't make and was easily detected 48 hours later in the blood.

The technique "represents an alternative paradigm for improved cancer detection," said the paper published in the U.S. journal Proceedings of the National Academy of Sciences. "If proven safe and effective, (it) eventually may have potential as a powerful cancer-screening tool for the general population."

The hunt for cancer "biomarkers" in the blood, or substances that indicate a probable tumor, is nothing new, but various tumor types naturally secrete characteristic substances with each requiring its own separate test, said Prof. Sanjiv Gambhir, the study's senior author, chair of radiology and director of the Canary Center at Stanford for Cancer Early Detection.

Complicating matters, these substances are also quite often made in healthy tissues, so a positive test result doesn't absolutely mean a person actually has cancer. In addition, a tumor, especially a small one, simply may not secrete enough of the trademark substance to be detectable.

Gambhir's team found a way to force any of numerous tumor types to produce a biomarker whose presence in the blood of mice unambiguously signifies cancer, because none of the rodents' tissues would normally be making it.

"This biomarker is a protein called secreted embryonic alkaline phosphatase (SEAP)," they said in a statement. "SEAP is naturally produced in human embryos as they form and develop, but it's not present in adults."