Incidence trends in bladder and lung cancers between Denmark, Finland and Sweden may implicate oral tobacco (snuff/snus) as a possible risk factor

Abstract

Background The dominant risk factor for urinary bladder cancer has been cigarette smoking, but, as smoking prevalence is decreasing in many populations, other risk factors may become uncovered. Such new risk factors could be responsible for halting the declining incidence of bladder cancer. We hypothesize that snuff use by Swedish men may increase the rate for bladder cancer, as snuff contains carcinogenic nitrosamines. Methods We carried out an ecological study by comparing incidence trends in lung and bladder cancers between Danish, Finnish and Swedish men in order to test if the Swedish bladder cancer rate deviates from the Danish and Finnish ones. We used the NORDCAN database for cancer data from 1960 through 2016 to test the hypothesis. Results In the three countries, the incidence of lung cancer started to decrease after a peak incidence, and this was later followed by declining incidence in bladder cancer in Denmark from 1990 to 2016 by 14.3%, in Finland by 8.3% but not in Sweden (the decline of 1.4% was not significant). The difference in trends can be partly explained by the increasing incidence in Swedish men aged 70 or more years. Sweden differs from the two other countries by low male smoking prevalence but increasing use of snuff recorded by various surveys. Conclusion The stable bladder cancer trend for Swedish men was opposite to the declining trends in Denmark, Finland and globally. We suggest that this unusual finding may be related to the increasing use of snuff by Swedish men. Average users of snuff are exposed to at least 3 times higher levels of carcinogenic tobacco-specific nitrosamines than a smoker of one daily pack of cigarettes.

Incidence and survival in oral and pharyngeal cancers in Finland and Sweden through half century

“…Smoking prevalence declined fast for SE men [ 32 ]; they reduced their daily smoking prevalence from 28.4% in 1988/89 to 15.7% in 2004/05 to the lowest level among European men, while among FI men 35.5% smoked in 1988/89 and 28.0% smoked in 2004/05 [ 33 ]. SE men compensated tobacco smoking by oral tobacco (snuff/snus) but this habit seems not to cause oral cancer [ 27 , 33 – 35 ]. Among SE women smoking prevalence slowly decreased to about 20% in 2000 matching prevalence of FI women for whom the prevalence had slowly increased.…”

“…After 2000, female smoking prevalence slowly decreased in both countries [ 36 ]. The incidence in lung cancer in SE women exceeded that of SE men after 2010 which was an epochal incidence crossing in the history of tobacco carcinogenesis [ 27 , 35 ]. We hypothesize that the reduction in smoking level and modest consumption of alcohol among SE men helped to stop the increasing trend in cancer of the oral cavity [ 36 ].…”

Survival in bladder and upper urinary tract cancers in Finland and Sweden through 50 years

“…Smoking increases complications in bladder cancer treatment and survival, but smoking prevalence is an unlikely explanation for men because Swedish men have had the lowest smoking frequency in Europe [ 37 – 40 ]. As an opposite trend, use of oral tobacco (snus) has increased among Sweden men (1988 19%, 2004 27%), and a combined daily use of either form of tobacco product has remained constant in Sweden (1988 43%, 2004 40%) [ 37 , 41 ]. While the use of oral tobacco has also increase among Swedish women (1988 1%, 2004 4%) and Finnish men (1988 nil, 2004 3%) its use in these groups is still relatively uncommon and not likely to affect our results [ 37 ].…”

“…In women daily smoking has been more common in Sweden (1988 32%, 2004 20%) than in Finland (1988 20%, 2004 21%) [ 37 ]. Snus may increase the risk and mortality of some cancers but only indirect data are available on its possible influence on survival in bladder cancer [ 41 , 42 ]. However, trends in smoking and the use of oral tobacco might explain why Swedish males and females lost their lead in 5-year survival to their Finnish counterparts.…”

“…While 5-year survival remained more than 10% unit below 1-year survival, it was worrisome that after the early 1990s the gap (difference) between 1-and 5-years survival narrowed only modestly, if at all. Further improvements in survival call for control of smoking, assessment of the role of snus in Sweden [ 41 ], emphasis on early diagnosis, including prompt cystoscopy and imaging investigations in hematuria, and upfront curative treatment with surgery and adjuvant therapies, combined with awareness of high relapse rates in treated bladder cancer patients requiring regular cystoscopy follow up.…”