25 June 2015
A team at John Hopkins University have identified DNA of head and neck tumours in the blood and saliva of a number of patients.
The researchers published their findings in the journal Science Translational Medicine and say the study could lead to better cancer screening tests.
Dr Nishant Agrawal, associate professor of otolaryngology and oncology at the Johns Hopkins University School of Medicine, said the research demonstrated that tumour DNA can be picked up from blood or saliva. This, according to the researchers, could offer the best chance of detecting cancer in these areas.
"In our study, testing saliva seemed to be the best way to detect cancers in the oral cavity, and blood tests appeared to find more cancers in the larynx, hypopharynx and oropharynx. However, combining blood and saliva tests may offer the best chance of finding cancer in any of those regions," Dr Agrawal said.
Inborn genetic predispositions for most head and neck cancers are rare, but other mutations that don't generally occur in normal cells have long been considered good targets for screening tests, he explained.
Along with his team, Dr Agrawal analysed the blood and saliva of 93 patients who had been recently diagnosed with head and neck cancer. They looked for certain tumour-promoting, HPV-related DNA, as well as searching for TP53, PIK3CA, CDKN2A, FBXW7, HRAS and NRAS for non-HPV-related cancers.
The study found DNA from tumours in the saliva of nearly three-quarters of the patients (76 per cent) and in the blood of 87 per cent. When the team looked at how well their tumour DNA tests found cancers in certain regions of the head and neck, they found that saliva tests fared better than blood tests for oral cavity cancers.
Dr Agrawal said: "One reason that saliva tests may not have been as effective for cancer sites in the back of the throat is because we didn't ask patients to gargle; we only asked them to rinse their mouths to provide the samples."
However, he explains that the sensitivity of the tests overall depend on the cancer site, with results varying from 86 to 100 per cent. The team also found that saliva tests fared better for early-stage cancers.
The researchers warn that further investigation is needed to test the DNA detection method in larger groups of patients, including healthy people.
In addition, Dr Agrawal said: "We don't yet have definitive data on false positive rates, and won't until there are more studies of the tests in healthy people."
Posted by Phillip Briggs
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