Toluidine blue dye reveals oral cancers

Sep 1 2005

A team of Canadian scientists may have discovered a way to use a simple dye as a litmus test to identify abnormal areas of the mouth that may become cancers.

According to a study published in the September 1 issue of Cancer Research, the scientists found that lesions that took up the dye known as toluidine blue were six times more likely to become oral cancers.

The team also discovered that the dye-staining lesions contained molecular alterations that are linked to high risk of oral cancers -- even at early stages.

"In oral cavity lesions, tissue that stained positive with toluidine blue were more likely to advance to cancer than lesions that did not stain with the dye," said Miriam Rosin, Ph.D., Director of the BC Cancer Agency's British Columbia Oral Cancer Prevention Program and Professor, Simon Fraser University. Rosin is the senior author on the study, funded by the National Institute of Dental and Craniofacial Research, of the National Institutes of Health.

Toluidine blue is an accepted indicator of oral cancers, Rosin said. The current studies, however, demonstrate that the dye accurately predicts which pre-malignant lesions are likely to advance toward disease. Those lesions appear as white or, less frequently, red patches.

"The vast majority of those white patches are often from minor inflammation and irritation," Rosin said. Some, however, are inclined to become cancer--and are the ones targeted by this simple imaging technology.

In the study of 100 patients, Rosin and her colleagues learned that toluidine blue-stained lesions became squamous cell carcinomas more quickly than lesions that did not stain. The scientists also determined that dye-stained oral lesions were more likely to be aberrant not only at the gross tissue level but at the molecular genetic level as well. Toluidine blue was applied to lesions in the mouths of patients during dental visits to determine the value of the stain for imaging precancerous lesions.

"Oral premalignant lesions that stained with toluidine blue consistently contained loss of chromosomal genetic information," Rosin said. In patients with dye-stained lesions, Rosin and colleagues found a strong association with loss of genetic information, termed loss of heterozygosity (LOH), on one or more chromosomes.

"Patients with positively stained tissue had a higher incidence of LOH at multiple sites, including regions on chromosome arms 3p or 9p or both as well as on parts of other chromosomes" Rosin said. Rosin's Cancer Research article reports results from the initial phase of a long term study that followed 100 patients for 44 months. By the completion of the longitudinal study, Rosin and colleagues will monitor 400 patients.

The current report links the staining of cells with toluidine blue in mouth tissue to the higher risk of patients likely to develop squamous cell carcinomas. When biopsied, lesions that stained blue most often showed microscopic abnormal tissue development – dysplasia – that is associated with cancer risk.

The Rosin team then established that the dye-stained lesions had characteristic molecular alterations that are linked to higher risk for oral cancers -- even when the dye stained tissue is at an early stage, when dysplasia is minimal. Cells with molecular changes took up the blue dye before the lesion acquired extensive dysplasia. The findings are among the first steps in designing and implementing an imaging screening program that dentists and oral hygiene professionals can use to make first-line decisions about early stage biopsies and referrals for anti-cancer related care.

More than 300,000 people worldwide will be diagnosed with oral cancer this year. In the United States, 30,000 people will develop oral cancers. The five-year survival rate for oral cancer remains between 40 and 50 percent--a statistic that hasn't changed over the past several decades.

"The disease is usually identified fairly late in progression," Rosin said. "At that stage, it is frequently not amenable to the successful intervention that we'd like. The whole deal of changing survival outcome is that you have to get at the disease earlier."

British Columbia is a likely setting for developing a triage model to screen and identify high risk lesions among dental patients. Ninety percent of the Province's residents see a dentist at least once every two years. Approximately 2,500 dentists in British Columbia form a potential Province-wide screening network that will forward high risk patients to special care facilities.

"With enough training of those who are doing the screening, the dye should help the clinicians find those patients with lesions that should really be moved forward for assessment," Rosin said. Training and technology should enable the people at the point of screening to determine whether the lesion should be monitored, or if the patient should be referred for further assessment. In some cases, the dentist can decide immediately whether a biopsy should be taken at that point.

The multidisciplinary research team that collaborates with Rosin includes pathologists, oral medicine specialists, dentists, oral surgeons, radiation oncologists, molecular biologists, statisticians and epidemiologists.

Her colleagues include, the lead author on the publication, Lewei Zhang, Catherine Poh, Robert Priddy, University of British Columbia; Michele Williams, Joel Epstein, Scott Durham, Nhu Le, Greg Hislop, John Hay, Wan Lam, British Columbia Cancer Agency/Cancer Research Center; Hisae Nakamura, Denise Laronde, Simon Fraser University; and Ken Berean, Vancouver Hospital and Health Sciences Center, Vancouver, B.C., Canada.

http://www.aacr.org/