Although tobacco use is still one of the strongest risk factors associated with mouth cancers, precancerous lesions in the mouths of non-smokers are more twice as likely to progress to cancer than those in smokers, according to the University of British Columbia (UBC) and BC Cancer. Also, lesions in non-smokers progress to cancer faster than smoking-associated lesions.
“This is the first published study where the main focus was to examine the difference in risk of progression to oral cancer between non-smokers and smokers with oral precancerous lesions,” said Leigha Rock, a PhD candidate at UBC and coauthor of the study. “While other studies have also reported a higher rate of transmission among non-smokers, we looked at multiple risk factors including genetic markers.”
The researchers examined the case history of 445 patients with oral epithelial dysplasia (OED), a type of precancerous oral lesion, enrolled in the British Columbia Oral Cancer Prediction Longitudinal Study. One-third of the patients were non-smokers.
“As smoking rates decline, we are seeing an increase in the proportion of these types of lesions in non-smokers,” said Rock.
Lesions on the floor of the mouth in non-smokers were 38 more times more likely to progress to cancer than they were in smokers. The study also is the first to report on quicker progression to cancer in non-smokers, as both the three-year and five-year rates of progression were 7% and 6.5% higher than smokers, respectively.
The researchers suggest the marked difference in outcomes is due to a difference in the root causes of the lesions. In smokers, the OED is likely the result of environmental factors, whereas in non-smokers, genetic susceptibility or mutations are likely to blame.
“Our findings show that molecular genomic markers can identify high-risk lesions, regardless of risky habits like smoking, and should be an important consideration in patient management,” said Rock.
The study’s results stress the importance of taking oral lesions seriously, especially when they occur in non-smokers, the researchers note.
“If you see a lesion in a smoker, be worried. If you see a lesion in a non-smoker, be very worried. Don’t assume it can’t be cancer because they’re a non-smoker. Our research indicates non-smokers may be at higher risk,” said Rock.
The study, “Characterization of epithelial oral dysplasia in non-smokers: First steps towards precision medicine,” was published by Oral Oncology.