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 exposure	3.6
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.

Nebraska Legislature Passes Tobacco Harm Reduction Resolution

The Nebraska legislature on March 27 passed resolution LR 499 to “recognize the importance of tobacco harm reduction strategies as an additional choice to assist cigarette smokers in quitting.” (website here). The measure was introduced by Senator Bob Krist (District 10).
The resolution’s rationale is simple: “many persons addicted to cigarette smoking are unable to quit,” and “studies show that smokeless tobacco presents a fraction of the health risk of smoking cigarettes.” It observes that “Tobacco control policies that facilitate the migration of smokers to less risky smokeless products may be more effective at reducing the deaths, diseases, and expenses associated with smoking than policies that rely solely on the abstinence-only approach.”

Nebraska’s legislature is the third (the second this year, discussed previously here) to recognize the potential for safer smoke-free tobacco products to serve as cigarette substitutes for inveterate smokers.

Nebraska has the only unicameral (one chamber) and only nonpartisan legislature in the nation (more information here). The 49 senators further distinguished themselves by resolving to make the lives of Nebraska smokers a higher priority than the abolition of all tobacco products.

From Norway: Snus Risk Perception Can Drive Smoking Cessation; The Right to Truth and Health

Norway has been documented recently as the second European country to embrace the substitution of snus for cigarettes, confirming the “Swedish experience” of tobacco harm reduction. Karl Erik Lund, a researcher at the Norwegian Institute for Alcohol and Drug Research, has published a series of studies illustrating the “Norwegian experience” (here and here). His newest study shows that a smoker’s willingness to try snus is closely correlated with one’s perception of the product’s health risks relative to cigarettes. The study appears in Nicotine & Tobacco Research (abstract here).

Dr. Lund used a survey of 14,700 men age 20-50 years with a 49% response rate. Participants included 1,155 former smokers and 1,417 current smokers (80% of whom had tried to quit).

Snus, used by 32% of former smokers, was the most common method used to quit smoking. Nicotine gum was a distant second, at 14%.

Dr. Lund measured perceptions among current and former smokers of the risks of snus compared with cigarettes. Here are the results for former smokers:

Perception of Snus Risk Among Former Smokers
	Percent
Far more or somewhat more risky	3
About the same	31
Somewhat less risky	35
Far less risky	32

Compared with former smokers who incorrectly believed that snus has the same or higher risks compared to cigarettes, the 32% of smokers who correctly believed that snus was “far less risky” were 11 times more likely to have used snus to quit smoking. In addition, the “somewhat less risky” group was 3.5 times as likely to have used snus.

Perceptions among current smokers also had important implications:

Perception of Snus Risk Among Current Smokers
	Percent
Far more or somewhat more risky	3
About the same	37
Somewhat less risky	37
Far less risky	23

Compared with smokers who incorrectly believed that snus has the same or higher risks than cigarettes, the 23% of smokers who correctly believed that snus was “far less risky” were five times more willing to try snus in a future quit attempt. In addition, the “somewhat less risky” group was over twice as likely to try snus.

Dr. Lund described the implications: “The main finding in our study was that correct perception of the relative risk between snus and cigarettes was positively correlated with having used snus when quitting smoking. Likewise, among current smokers, correct beliefs of differential risks between the two products were positively correlated with the willingness to use snus in future quit attempts. Thus, providing accurate risk estimates to smokers may not only have an ethical justification, dissemination of such information might also result in increased quit rates for smoking.

“Lacking any compelling evidence of net harm to society from correcting misperceptions of the relative risk between cigarettes and snus, the human right for the individual to receive accurate information about options to reduce risk should prevail. Going beyond the no-safe-tobacco message to provide better informa¬tion … is necessary to respect the individual right to health relevant information and smokers’ autonomy and may also—as our study indicates—result in increased quit rates for cigarette smoking. Some have argued that failure to disseminate infor¬mation about reduced risks for fear that population nicotine use may increase could be regarded as paternalism and create public mistrust of health messages about tobacco use. To prevent uptake of snus among youth, public health and tobacco control professionals could use other methods than withholding information about relative risks, including taxation, restrictions, and information campaigns aiming to change the cultural symbolism of snus use…Devising a way to inform smokers about the risk contin¬uum of tobacco products (without anyone decoding this infor¬mation as snus being risk free) should be an important research priority in countries where snus is allowed to compete with cigarettes for market share.”

In the U.S., where smokeless tobacco products compete with cigarettes, public health authorities must begin to communicate truthful information about the differential risks to smokers. Disinformation and obfuscation about the relative risks of varying tobacco products costs lives and disgraces those who pursue such actions. Truthful communication about tobacco harm reduction is a public health imperative.

Human Papillomaviruses and Oral Cancer

For many decades smoking and alcohol abuse were the major risk factors for oral cancer. In contrast, smokeless tobacco use, while commonly misperceived as a common cause, has played virtually no role. Now, there is emerging scientific evidence that human papillomaviruses (HPVs), which are recognized to cause cervical cancer in women, may cause oral cancer. A new study by Anil K. Chaturvedi, from the National Cancer Institute, and investigators from five other institutions, provides evidence that HPVs have played an increasing role in some cancers of the mouth and pharynx (abstract here).

Chaturvedi and colleagues looked for HPVs in cancers of the base of tongue, tonsil and oropharynx collected by cancer registries in Hawaii, Iowa and Los Angeles from 1984 to 2004. They found that HPVs were present in only 16% of tumors during the 1980s, but by 2004 over 70% of these tumors were HPV positive.

Chaturvedi and colleagues concluded that “HPV-positive [oropharyngeal cancers] will likely constitute a majority of all head and neck cancers in the United States in the next 20 years,…” and “by 2020, the number of HPV-positive [oropharyngeal cancers] is expected to surpass the number of cervical cancers, the focus of prophylactic HPV vaccination.” The investigators argued for “evaluation of the efficacy of vaccination to prevent oral HPV infections, particularly given the unavailability of screening for [orophyyngeal cancers].”

It is important to note that Chaturvedi only looked at a subset of mouth and throat cancers. Oral cancer also occurs under and on the sides of the tongue, and these tumors are less likely to be HPV positive.

The authors note that “[oropharyngeal cancer] incidence increased from 1973 to 2004 in the United States, particularly among young individuals (< 60 years of age), men, and whites.” However, they didn’t provide the perspective that oral cancer is a very rare disease. I have analyzed the National Cancer Institute’s cancer registry; in 2003, there were only 10,400 cases of oral cancer in the United States, and there were 12,200 cases of pharynx-throat cancer (reference here). I wrote that “[i]f every oral cancer was detected by one of the 128,000 general dentists in the United States, then on average each dentist would make one diagnosis every 12 years.”

The authors classify the cancers into HPV positive and negative, and they write that “the declining incidence of HPV-negative [oropharyngeal cancers] parallels declines in smoking in the United States.” However, very little is known about the interaction between HPV and smoking or alcohol use.

Chaturvedi and colleagues make a good case that the increasing number of HPV-positive oropharyngeal cancers “argues for evaluation of the efficacy of vaccination to prevent oral HPV infections...” Vaccination has the potential to reduce the incidence of cervical cancer among women, and further to reduce HPV infections among both women and men.

If vaccination is a no brainer for cervical cancer and for HPV-positive oropharyngeal cancer, what about cancer caused by smoking? The epidemiologic evidence documents that smokeless tobacco and e-cigarettes have the potential to immunize smokers against these and other deadly illnesses.