>Indeed, although ST studies indicate that ST increases the risk of oral cavity and pancreatic cancer, at least for some forms of ST (9–11), both are substantially less than the risk of these cancers from smoking (11, 12). The former risk seems to be a consequence of exposure to tobacco-specific nitrosamines (TSNA) because in Sweden, where ST products are produced in a way to substantially reduce TSNAs, the risk of oral cavity cancer does not seem to be increased (11).

>Still, it should be noted that the risk of pancreatic cancer from low-TSNA tobacco is substantially lower than from smoking, and so this comparison adds reassurance for the long-term safety of NRT.

>A smoking cessation study by Stepanov and colleagues, however, showed that NNK metabolites were not detectable in persons using NRT (34, 35). However, they did find intermittently high levels of NNN similar to baseline smoking levels among some oral NRT users and in 1 of 9 persons using the NRT patch (36). Although these data indicate a potential cancer risk to NRT users, especially oral users, it is important to realize that NNN is only one of the TSNAs in cigarette smoke, let alone of the many other tobacco smoke carcinogens, and so in this context the risk, if any, seems small compared with continued smoking.

[1] http://cancerpreventionresearch.aacrjournals.org/content/4/1...