Doctors may soon have a new weapon in their fight against breast cancer, say researchers working on a simple blood exam to reveal how the body processes metals.

By detecting alterations in the trace metal zinc inside our bodies, the test could yield earlier diagnosis of breast cancer, says the team headed by scientists at Oxford University in Britain.

Changes seen in the isotopic composition of the zinc detected in a patient's breast tissue could possible identify a "biomarker," or measurable indicator, of the early stages of breast cancer, the researchers report in Metallomics, a journal of the Royal Society of Chemistry.

They took a technique normally utilized to detect trace metal isotopes for studying climate change and planetary formation and used them to analyze how human body processes metals.

It is more than 100 times as sensitive to changes in isotopic compositions of metals than anything presently available to clinicians, the researchers say.

Analyzing zinc in the blood of ten subjects -- five breast cancer patients and five healthy controls -- the researchers could detect subtle but important differences in isotopic zinc that result when cancer subtly changes the manner in cells deal with the metal.

Similar changes seen in copper in one of the study's breast cancer patients suggests trace metals could be a valuable clue in cancer diagnosis.

"It has been known for over a decade that breast cancer tissues contain high concentrations of zinc but the exact molecular mechanisms that might cause this have remained a mystery," says Oxford research leader Dr. Fiona Larner of the university's Department of Earth Sciences.

The new analysis technique, common to earth science research, if it reveals how breast cancer can be traced to changes in zinc in a person's blood, can hold out "the promise of an easily-detectable biomarker of early breast cancer," Larner says.

The technique, which could be the basis for a simple, non-invasive, diagnostic blood test, may also lead to the development of advanced treatments for cancer, she adds.

"The hope is that this research is the beginning of a whole new approach," Larner says. "Understanding how different cancers alter different trace metals within the body could enable us to develop both new diagnostic tools and new treatments that could lead to a 'two-pronged' attack on many cancers."

The technique could identify biomarkers of the first stages of breast cancer long before any overt symptoms appear, the researchers suggest.