Clinical interventions are vital to slash the burden of disease associated with smokeless tobacco, and providing cessation treatment in clinical settings is critical, say researchers.
In a recent perspective in The New England Journal of Medicine, Mark Parascandola, Suzanne Nethan and Kamran Siddiqi write:
Smokeless tobacco (ST) use is a leading contributor to oral cancer and mortality worldwide – but both ST use and oral cancer are preventable.
ST products are used by more than 360m people in 140 countries. Most of them (77%) are in low- and middle-income countries (LMICs), especially in Southeast Asia. ST use is particularly high in Bangladesh, India, Pakistan and Papua New Guinea.
And whereas rates of cigarette smoking have declined in most countries in recent decades, ST use has been increasing.
ST is classified by the International Agency for Research on Cancer (IARC) as a group 1 carcinogen in humans.
According to data from GLOBOCAN (Global Cancer Observatory), the incidence of oral cancer, the primary type of cancer linked to ST, has been increasing, particularly in countries with high ST use.
There were 389 846 new cases of oral cancer globally in 2022. In South Asia, oral cancers are the most common cancers among men. By far the largest numbers of oral cancer cases and deaths occur in India – not surprising, given its population size and prevalence of ST use.
ST products are made, entirely or partly, from tobacco leaves or extract and are consumed orally without being burned. The category encompasses a diverse array of manufactured and custom-made products, including chewing tobacco, snuff, gutka, khaini, betel quid with tobacco, snus, toombak, and iqmik.
ST products often include other ingredients for added flavour or to enhance nicotine delivery. Areca nut, widely used in South Asia, Southeast Asia, and the Pacific, is itself a group 1 carcinogen with addictive properties.
According to a recent estimate, more than 120 000 cases of oral cancer (30%) were attributable to ST use, areca nut use, or both in 2022. The most cases attributable to ST use (87.8%) occurred in south-central Asia, followed by south-eastern Asia and eastern Asia.
Although the cancer risks posed by ST use are well documented, the proportion of oral cancers attributed to ST use varies with the prevalence of use and with particular product characteristics, patterns of use, and the prevalence of other carcinogenic exposures (e.g., smoking, alcohol use, or human papillomavirus).
In India and Sudan, according to a 2008 review, more than 50% of oral cancers were found to be attributable to ST, compared with about 4% among men in the United States. Both ST use and oral cancer disproportionately affect LMICs and populations with lower incomes and levels of education.
Furthermore, prognosis and survival among patients with oral cancers are disproportionately worse in LMICs.
The differences in attributable risk of cancer are also driven by the diversity of product types and modes of use around the world.
The levels of known carcinogens and other harmful constituents in ST products vary widely among regions and even among products within the same market, as a function of the tobacco type, the processing method, storage conditions, and added ingredients.
In LMICs, ST products are often manufactured in local cottage industries or assembled by street vendors, which introduces greater variation. In India alone, ST has grown into a multimillion-dollar industry, with more than 400 brands.
Flavoured nicotine pouches, without tobacco, have also appeared on the market in some countries.
ST use continues to increase, particularly in countries that already face a high burden of use and related health effects. Since 2000, ST use has increased (in absolute terms and as a proportion of all tobacco use) in Bangladesh, India, and Nepal (in India, ST accounts for 61% of total tobacco use).
In addition, unlike cigarette smoking, ST use is seen as socially acceptable and hence is popular among women in some countries. For example, in Burkina Faso, the majority of tobacco use among men (80%) is in the form of cigarettes, whereas women who use tobacco almost exclusively choose ST.
Increased uptake of ST among young people also poses a major public health challenge.
Data from the Global Youth Tobacco Survey covering 12-to-16-year-olds in 138 countries indicate that the overall prevalence of ST use was 4.4% between 2010 and 2019, though the percentage varied according to location, was much higher among boys than among girls, and increased with age.
The prevalence of ST use among young people is particularly high in Western Pacific island countries, including the Marshall Islands (26.1%), Micronesia (21.3%), Palau (16.0%), and Papua New Guinea (15.2%).
Over the past few decades, ST product manufacturers have used new formulations and marketing techniques to appeal to young people, including manipulating nicotine content, using attractive flavourings, and developing products that can be used discreetly in situations or places where cigarette smoking is prohibited.
Despite the documented adverse health effects of ST, research on ST and policies designed to reduce its use have generally lagged behind those for cigarettes, particularly in LMICs.
Nevertheless, there are important opportunities and critical actions that health professionals can take in clinical settings to intervene in cases of tobacco use and to prevent oral cancers caused by ST.
These interventions are relevant not only to LMICs with the highest burden, but also to the United States and other high-income countries where ST use is prevalent in particular subgroups, such as South Asian immigrants and people living in rural areas.
According to the IARC, there is sufficient evidence that behavioural interventions in adults are effective in helping people to stop using ST, although the evidence for pharmacologic interventions (alone or combined with behavioural interventions) is still emerging.
A recent systematic review showed similar evidence, revealing substantial efficacy of behavioural interventions for cessation and limited evidence supporting varenicline and nicotine lozenges.
An updated Cochrane review has also shown that higher ST abstinence rates are achieved with behavioural interventions than with minimal support, and higher rates are achieved with brief advice than with no support.
Varenicline and nicotine replacement therapy probably also improve ST quit rates, though the supporting evidence is of low certainty.
Although most of the evidence to date comes from high-income countries, studies are under way in LMICs burdened by ST use. On the basis of this combined evidence, the World Health Organisation recommends offering behavioural interventions, varenicline, or nicotine replacement therapy for ST users who are interested in quitting. Although health professionals are now increasingly likely to counsel patients about cigarette smoking, they frequently overlook ST use.
Education and training programmes for health professionals generally do not provide up-to-date information on ST use – particularly in certain populations – and its associated risks and cessation interventions. Health professionals who have regular contact with patients have many opportunities to talk with and counsel them about tobacco use, including ST.
During a simple oral examination, dentists and doctors not only can detect early signs of health effects, such as oral precancerous lesions in patients using ST, but they can also use such an examination as a “teachable moment” to encourage patients to quit.
Though evidence does not support oral cancer screening for the general population, studies in high-risk groups, including ST and areca nut users, have revealed a potential benefit from screening for early detection of oral cancers or precancerous lesions.
Further research is needed, but asking about ST use and providing cessation treatment in clinical settings remains a critical avenue for addressing ST use and preventing oral cancer.
Mark Parascandola, Ph.D – .National Cancer Institute, Bethesda, MD;
Suzanne Nethan, M.D.S –International Agency for Research on Cancer, Lyon, France;
Kamran Siddiqi, Ph.D – Hull York Medical School, University of York, York, United Kingdom.
See more from MedicalBrief archives:
Global deaths due to smokeless tobacco up by a third – UK Study
Smokers misunderstand risks of smokeless tobacco product snus
Tobacco harm reduction – The stunning success of snus in Sweden
Politically charged European Court of Justice rules for continued ban on snus