Much of the following is taken from Rodu and Godshall's Tobacco harm reduction: an alternative cessation strategy for inveterate smokers. See the original for further reading or for details on the research behind the conclusions.
Oral leukoplakia is an ominous sounding term used frequently in discussions about oral lesions resulting from ST use. The term literally means "white plaque," and it is used to describe areas of the mouth lining that become thickened by ST use or smoking. The World Health Organization has determined that leukoplakias resulting from ST use are considerably different from those resulting from smoking. The distinctions are based on the frequency of occurrence, the location in the mouth, and how often these leukoplakias result in mouth cancer.
The condition is rare, occurring in less than 1% of the general population, primarily in long-time smokers 40 to 60 years old. Smoking-related leukoplakias most commonly involve the undersurface of the tongue and throat area, locations that account for 75% of oral cancer in the U.S..
Oral leukoplakias occur in up to 60% of ST users, within 6 months to 3 years of starting ST use. They primarily occur at the site of ST use and are largely a result of local irritation. The frequency of appearance depends on the type of ST that is used. Moist snuff, which is more alkaline than chewing tobacco, more often leads to leukoplakia. However, moist snuff in pre-portioned pouches (like snus) causes fewer cases of leukoplakia than does the loose form.
There are distinct differences in how often ST and smoking leukoplakias show pre-cancerous changes called dysplasia. Dysplasia is seen infrequently in ST leukoplakias (less than 3%). Furthermore, even when dysplasia is present in ST leukoplakia, it usually is found in earlier stages than in leukoplakias among smokers, where it is seen in about 20% of cases.
ST leukoplakias only rarely progress to cancer. For example, one study found no case of cancer in 1,550 ST users with leukoplakia who were followed for 10 years, and a second study reported no case of oral cancer among 500 regular ST users followed for six years. A retrospective study of 200,000 male snuff users in Sweden found only one case of oral cancer per year, an extremely low frequency. In comparison, a follow-up study reported that 17% of smoking leukoplakias transformed into cancer within seven years.
In conclusion, oral leukoplakia occurs commonly in ST users, but it primarily represents irritation and only very rarely progresses to oral cancer.
