U.S. scientists are developing a screening test for breast cancer that checks a woman's saliva for evidence of the disease to help find tumours early, when they are most treatable.
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 tumours and those with malignant breast tumours.
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, produced by tumour cells, affect cell growth, cell metabolism and cell self-destruction – all of which go awry in cancer, Dr. Streckfus said.
He and his colleagues tested saliva from 30 women – 10 healthy, 10 with malignant breast cancer and 10 with benign tumours.
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, Dr. Streckfus said. But U.S. government approval for the test may be sought within five years.
Focus on developing countries
Mammography and breast self-examination for tumours are leading methods used for early detection of breast cancer.
But Dr. Streckfus said mammograms – X-rays of the breasts – are too expensive in many developing countries, so a cheap, easy-to-perform screening test would be valuable.
"On a global perspective, mammography is not very common," he said in a telephone interview. "Even in our neighbour, Mexico, there are very few mammography centres around."
Dr. Streckfus said he envisioned a saliva test as a quick, inexpensive and simple screening method. In developed countries like the United States or Canada, he said, such a test could complement existing screening methods.
Breast cancer is the leading cause of cancer death among women worldwide, the American Cancer Society says.
The organization estimates that 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 that women 40 and older get a mammogram every year. Dr. Streckfus said the new test could be done more frequently to find tumours that might arise between mammograms.
Other researchers said last week that 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.
