Wednesday, January 6, 2016

Chewers and Dippers: Beware Bogus Mouth Cancer Claims by Dentists and Others

As a practicing oral and maxillofacial pathologist for over 25 years in the Southeast U.S. – also known as Smokeless Tobacco Country – I diagnosed over a thousand mouth cancers in smokers and heavy drinkers, but few in nonsmokers who used moist snuff or chewing tobacco.  Large epidemiologic studies conducted over the past 40 years confirm the much higher mouth cancer risk posed by cigarettes versus smoke-free products (here and here). 

Recognizing the public health impact of this data, I have given hundreds of lectures to dentists and other health professionals about the benefits of switching inveterate smokers to safer smoke-free tobacco – a scientifically validated form of harm reduction.  On occasion, I am confronted by a dentist who insists that they have seen in their practice many oral cancers caused by smokeless tobacco.  Given that smokeless tobacco users’ cancer risks are no higher than those of nonusers (discussed here and here), the possibility of a dentist seeing numerous smokeless-related cancers is remote.  A dentist in Oklahoma recently made that claim to one of my tobacco harm reduction colleagues.

To test the validity of that claim, we can focus on data involving men age 45 and older, as smokeless tobacco use among women is rare.  Incidence (new case) rates for mouth cancer in Oklahoma are unknown, but CDC data reveals (here) that the death rate from mouth cancer among men in Oklahoma is about 11% higher than the U.S. rate.  From that, we can assume that the Oklahoma incidence rate is also 11% higher. 

According to the Surveillance, Epidemiology and End Results (SEER) program at the National Cancer Institute (here), the national incidence rate for mouth cancer is 23 cases per 100,000 men age 45+ years per year.  With census data showing there are 716,468 men age 45+ years in Oklahoma, applying the 11% adjustment we can extrapolate that there are 183 cases of mouth cancer in Oklahoma annually.

If every case of mouth cancer in Oklahoma was diagnosed by the state’s 2038 dentists (here) – and that is highly unlikely – on average, each dentist would see one case every 11 years.  (This estimate is similar to one we provided in a research article in 2007 -- abstract here).  Some dentists might see an unusually large number of smokers and heavy drinkers in their practice, so they might see a few more mouth cancers.  But their totals would still be minuscule.

The fact is, dentists and other general health professionals do not see high numbers of dippers and chewers with mouth cancer.


Carl V Phillips said...

Another reason why those claims are implausible: Recall that you and I ran the numbers once and determined that on average, a (regular) dentist would detect 0.5 cases of oral cancer during his entire career.

Carl V Phillips said...

After reading the post a little more carefully on the third pass, I realize I need to clarify my last comment (that will teach me): In contrast with that 2007 estimate you and Phil did, I recall that we were responding to the "keep an eye out for oral cancer!!!" advice to dentists. So we narrowed it down to the cases that were in the areas of the mouth that a dentist could actually see a lesion before it became so advanced (painful and such) that a pathologist like yourself or another medical provider would be consulted. So those were the ones that a dentist would plausibly be the one to detect.

Also, have you seen any updates to the RR estimates for the real effects of drinking (and smoking), given that it used to be claimed that they caused 75%+, but now we think that HPV causes in the range of half. That almost certainly means the official numbers are wrong (though it could be that many cases are multifactorial, caused by both HPV and a chemical exposure).

Unknown said...

If you want to delve further into the lunacy of a dentist making such claims(I once heard a practicing dentist claim he had diagnosed five oral cancers over his 27 year career, and could comfortably attribute three of them to smokeless tobacco.), one could focus solely on oral cancers that are more likely to occur in smokeless users (gum and cheek). Then you would see more like 5 cases in 100,000 men, of which many dentists would never see over the course of his career.

Anonymous said...

Dr. Rodu,

I have read your posts over the last several years and just want to express how thankful I am for your insight, acuity and critical application of science and statistical analysis in regards to smokeless use. Thank you.
I have enjoyed very light cigar use over several decades. As I have gotten older I have become slightly intolerant to smoke in general and sought out smokeless (ST) products as a way to enjoy the taste of tobacco without the smoke & time requirements to sit down with a good cigar.
To my knowledge I am neither addicted to nor do I care for the effects of nicotine but the flavor of a dark tobacco after a good meal or in the morning with a cup of coffee is just a little piece of heaven in a world that increasingly seems to be filled with difficulty, competition and increasing global conflagration.
As I am mindful of my health I am concerned about the potential carcinogenicity of ST. I am predisposed to the American ST products, particularly several of the Copenhagen brands due to their rich smokey taste and the expectoration which I enjoy. Always a light user (1 - 3 cans a year) I have now moved to snus seeking the lower TSNA loads and healthier manufacturing processes afforded by the Scandinavian product. Here too though I recently read some reports from the Mayo Clinic and others now warning of the consequences of snus use, particularly the purportedly elevated instances of pancreatic cancer in conjunction with snus use and I think, good gracious... is there any way to use this product without incurring some horrible, long-term outcome?
Your research and clear, accessible postings on this issue have allowed me to surmise that, "something's rotten in the State of Denmark," with regards to popular conceptions both in the public and the medical professional with regards to the dangers of ST/snus use.
I noticed several years ago in the rural area in which I work and live, that among several people I know who have been daily Copenhagen ST users for decades, they have reported zero issues with their oral health or any other problems they are aware of. I am also aware of two people from my professional contacts who would have appeared to have both lost teeth due to American smokeless use. However on the balance I have known many more people with decades of American ST use with no recognizable problems. Thus began my suspicion that at least anecdotally, American ST (fire cured/fermented) ST use just doesn't strike me as devastatingly dangerous as some sectors would have us believe. Your scientific and statistical results posted on this site would add credence to this outlook.
I will continue to use ST/snus sparingly and will monitor this blog for ongoing developments to help me make informed decisions aside from the almost 24/7 deluge of ST naysaying coming out of US medical/governmental establishment.
Thank you for your hard work and continued maintenance of this site!

befrits said...

Dear Professor Rodu and dear Anonymous,

Anonymous, if you check back here on your comment I would suggest you carry using snus as you please and read the following blog post:

Professor: Male rates of pancreatic cancer in Sweden is 1 case higher per 100,000 in incidence and mortality in Sweden. Excess is all in all 50 cases nationally. If we were to, just for the hell of it, attribute every single one of those cases exclusively to snus use and split the "winnings" among only the snus users; we would still end up with no more than 50 cases/fatalities per year among 1 million snus users.

That would equate to a 99,6% harm reduction rate, since oral cancer from snus has been ruled out. It seems even Swedish Public health authorities no longer dare to point out cancer scares on anything but pancreas from snus use.

Incredibly crude way of calculating and grossly overstated, but pretty functional to put things in perspective. It also seems to agree nicely with the Professors statements and research