Tuesday, April 24, 2012

I’m a Smokeless Tobacco User – Will I Get Mouth Cancer?

That’s a surprisingly common question, and one not easily answered. The task is made more difficult by the routine exaggeration of risks by anti-tobacco zealots. Still, it’s important to try.

First of all, risk is a complicated concept, so it is vital to understand all the information that is contained in a risk estimate. It starts with an incidence rate, which is the number of new cases of a disease that is seen in a population over a specified period of time. The Surveillance Epidemiology and End Results (SEER) program at the National Cancer Institute has collected information on incidence since 1973.

 SEER data reveals that there were about 34 cases of oral/throat cancer annually among 100,000 men ages 40-84 years from 2001 to 2006. This is an overall rate, which can be apportioned among the following groups: men who have not been exposed to known causes of oral cancer, current smokers, former smokers and alcohol abusers.

Non-exposed men make up about 45% of the population, and they have the baseline rate of oral/throat cancer (the relative risk, RR = 1.0). Current smokers make up about 25% of the population, and their RR for oral/throat cancer is eleven, compared with non-exposed men. Former smokers also comprise 25% of the population and have an RR of 3.4. Alcohol abusers comprise the remaining 5% and have an RR of 4.0. The overall incidence rate of 34 per 100,000 men per year is apportioned among the following groups:

Oral/Throat Cancer Among Men Age 40-84 Years Old in the U.S., 2001-2006
Exposure Group Rate (cases per 100,000 men per year)
No exposure3.6
Current Smokers 22.0
Former Smokers 6.8
Alcohol Abusers 1.6
All 34.0

What does this mean to the individual male user of moist snuff or chewing tobacco?

Dr. Philip Cole and I reviewed oral/throat cancer risks among smokeless tobacco users (abstract here) in 2002. We found that users of moist snuff (including snus) and chewing tobacco did not have risks that were significantly higher than those of nonusers of tobacco. Our findings were confirmed by a comprehensive meta-analysis of all epidemiologic studies of smokeless tobacco use and cancer (discussed by me here).

This exercise reveals that there are 3.6 cases of oral cancer among 100,000 smokeless tobacco users each year (or 36 cases among a million users), the same rate seen in non-exposed men. While it is not “zero” risk, it is no higher than the risk among men who are neither smokers nor heavy drinkers.

The concept of individual risk is also applicable to those individuals who believe they developed oral cancer due to smokeless tobacco use. Many such cases have become causes célèbres among anti-tobacco groups and the media. While all instances of cancer are distressing, associating one’s disease with a specific cause is highly problematic. Claims of causation should be examined objectively.

Scientific research has documented that cases of oral cancer associated with powdered dry snuff occur after decades of use. In one of the largest case series, powdered dry snuff users with oral cancer were on average 78 years old and had used the product for 55 years. Science may not support those oral cancer victims who blame smokeless tobacco for their condition if they used the product for less than two decades or developed cancer at a young age.

An objective investigation of a smokeless tobacco claim would consider other risk factors as well. Did the individual also smoke or use alcohol excessively? Has the person had a human papillomavirus (HPV) infection, which is now recognized as a cause of oral/throat cancer? These are important risk factors for oral cancer that should not be overlooked.

Finally, virtually everyone is at risk, however small, for every disease. Although oral cancer is rare, it most commonly occurs in smokers and/or heavy drinkers who are 50 years or older. However, as an oral pathologist, I have diagnosed oral cancer in 25-year-olds who didn’t smoke or drink.

Harm reduction doesn’t allow us to enjoy risk-free lives. It does give us valuable information to manage the risks of the activities that make life enjoyable.


Anonymous said...

And all this time I was told that smokeless tobacco and cigarettes were on the same level of risk. I was told this by dentists! The medical community should be ashamed!

Anonymous said...

In my experience health professionals tend to think everyone is high risk. They don't see the millions of people who have no problems every day. They only see the problems day in and day out. I believe a lot of health professionals have a skewed belief because of this. Go talk to a dermatologist who will tell you that you'll for sure get skin cancer if you don't cover up all your skin. This is because they see skin cancer all day long and see it as more of a pandemic than individual problem.

Thank you for this article. I have often wondered what the average time of use before cancer was.

Joseph said...

As a Dentist of 24 years and much of that time in a fishing community where many men chewed tobacco, I have NEVER seen one case of Oral Cancer in that population. Several among non-tobacco users.
For years I explained the risks and used the statistic of 2x relative risk......"which is double of nearly nothing", I would add. Now I tell my patients that we don't think it is even that high and the most important thing to do is move the site of chew placement around so as to minimize irritation and allow for a good examination; after all, if I can't see the cancer I cannot further evaluate it.

So when is intervention by society for the "Dangerous Addiction" necessary? How many baseball players have died of Oral Cancer? Out of how many baseball players total that chewed?Seems to me they ought to start with more deadly behaviors. For example, The death rate for motorcycle riders is around 72 per 100,000 registered motorcycles. This is the DEATH rate. I know, make all professional athletes drive cars. Silliness !!!!

Anders said...

There is no evidence that snuff or snus causes cancer.

Unknown said...

I've been saying this for years. Even had a debate with a friend last week. I told him to show me where it causes cancer. Now if people who use st don't take care of their mouth. Then that's where the big issue comes from