A cheap screening test that allows doctors and dentists to use blood and saliva to detect most oral cancers is in the pipeline, researchers say.

A new test that uses blood and saliva to detect head and neck cancers has shown promise in a small number of patients, researchers say.

While it will likely be years before the test is available to the public, the findings by researchers at Johns Hopkins University have raised hopes for a cheap screening test that dentists or doctors could one day deliver during regular office visits.

Head and neck cancers affect about 50,000 people in the US each year and are on the rise among men.

The main risk factors are alcohol, smoking and human papillomavirus (HPV), a common sexually transmitted infection that often goes undetected.

"We have shown that tumour DNA in the blood or saliva can successfully be measured for these cancers," said lead author Nishant Agrawal, associate professor of otolaryngology and oncology at the Johns Hopkins University School of Medicine.

The study involved 93 patients with cancer that had previously been diagnosed.

In patients known to have HPV-driven cancers, scientists searched patients' blood and saliva samples for certain tumour-promoting, HPV-related DNA.

In those with cancer not linked to HPV, they looked for mutations in a handful of cancer-related genes.

The researchers found tumour DNA in the saliva of 71 of the 93 patients (76 per cent) and in the blood of 41 of the 47 (87 per cent).

About half of the patients provided both saliva and blood samples to the scientists, and the combined tests found tumour DNA in 45 of those 47 people (96 per cent).

"Combining blood and saliva tests may offer the best chance of finding cancer," said Agrawal on Wednesday.

More trials on a larger number of patients are needed before the test can seek market approval.

An early form of the test may cost thousands of dollars, but down the road it could be offered for $50 in a dentist's office or primary care setting, the researchers said.

"Our ultimate goal is to develop better screening tests to find head and neck cancers among the general population, and improve how we monitor patients with cancer for recurrence of their disease," said co-author Bert Vogelstein, professor of oncology at the Johns Hopkins Kimmel Cancer Center.

The research is published in the June 24 issue of Science Translational Medicine.