WASHINGTON (Reuters) - Scientists in the United States are developing a screening test for breast cancer that checks a woman’s saliva for evidence of the disease to help find tumors early, when they are most treatable.

A color-enhanced MRI of a breast is seen in an undated file photo. Scientists in the United States are developing a screening test for breast cancer that checks a woman's saliva for evidence of the disease to help find tumors early, when they are most treatable. REUTERS/National Cancer Institute/Handout

In research published on Thursday, the scientists said they identified 49 proteins in saliva that the screening test would track to distinguish healthy women from those with benign breast tumors and those with malignant breast tumors.

Breast cancer triggers a change in the type and amount of proteins in secretions from the salivary glands, said Charles Streckfus, a professor of diagnostic sciences at the University of Texas Dental Branch at Houston.

The proteins are produced by tumor cells and affect cell growth, cell metabolism and cell self-destruction -- all of which go awry in cancer, Streckfus said.

Streckfus and colleagues tested saliva from 30 women -- 10 healthy women, 10 with malignant breast cancer and 10 with benign breast tumors.

The pattern of proteins is different in each of the three groups, the researchers reported in the journal Cancer Investigation.

More work needs to be done before a screening test based on these proteins can be made available to the public, Streckfus said. But U.S. government approval for the test may be sought within five years, he added.

FOCUS ON DEVELOPING COUNTRIES

Mammography and breast self-examination for tumors are leading methods used for early detection of breast cancer.

But Streckfus said mammograms -- X-rays of the breasts -- are too expensive in many developing countries and a cheap, easy-to-perform screening test would be valuable.

“On a global perspective, mammography is not very common,” Streckfus said in a telephone interview. “Even in our neighbor Mexico, there are very few mammography centers around.”

Streckfus said he envisioned a saliva test as a quick, inexpensive and simple screening method. In developed countries like the United States, such a test could complement existing screening methods, he added.

Breast cancer is the leading cause of cancer death among women worldwide, according to the American Cancer Society.

The organization estimated that about 465,000 women died from it globally in 2007, with 1.3 million new cases diagnosed. Declining death rates from breast cancer in developed countries have been attributed to early detection through mammography screening and to improved treatment, the organization said.

The American Cancer Society recommends women age 40 and older get a mammogram every year. Streckfus said the new test could be done more frequently to find tumors that might arise between mammograms.

Other researchers last week said they were developing a saliva test to screen for head and neck cancers. Their test also was years away from being available to the public.