Estimates of the current and future burden of cancer attributable to active and passive tobacco smoking in Canada
Introduction
In 1986, the International Agency for Research on Cancer (IARC) determined that there was sufficient human evidence to classify tobacco smoking and second-hand smoke as carcinogenic to humans (Group 1) (International Agency for Reseach on Cancer Working Group on the Evaluation of Carcinogenic Risks to Humans, 1986). The IARC working group concluded that tobacco smoking is associated with cancers of the lung, oral cavity, larynx, esophagus, bladder and pancreas. Cancers of the stomach, paranasal sinus, nasopharynx, liver, kidney, ureter, uterine cervix, ovary, colorectum and myeloid leukemia have since been added to the list in subsequent IARC monographs (International Agency for Reseach on Cancer (IARC), 2012; International Agency for Research on Cancer (IARC), 2004). A recent large meta-analysis showed that active tobacco smoking is also associated with breast cancer (Macacu et al., 2015). In addition, IARC concluded that there is sufficient evidence that secondhand smoke exposure (i.e. passive smoking) causes lung cancer (International Agency for Reseach on Cancer (IARC), 2012). Since the most recent IARC monograph on tobacco use in 2012, large meta-analyses have shown that secondhand smoke exposure (i.e. passive tobacco exposure) is also associated with an increased risk of colorectal, breast and cervical cancers (Macacu et al., 2015; Yang et al., 2016; Zeng et al., 2012).
There are many complex biological mechanisms hypothesized that link tobacco smoke to cancer. The most widely accepted mechanism involves the binding of inhaled carcinogens to DNA and forming DNA adducts, which in turn can cause miscoding and permanent mutations. These mutations can cause the loss of normal cell proliferation and lead to cancer when mutations occur in oncogenes or tumor suppressor genes (International Agency for Reseach on Cancer (IARC), 2012).
In 2012, an estimated 45,464 deaths from all causes in Canada were attributable to smoking tobacco and the total costs of tobacco use were $16.2 billion, including both direct and indirect health care costs (Dobrescu et al., 2017). Given these statistics, reducing the prevalence of smoking through prevention strategies should be a top priority for public health agencies. Previous analyses conducted in the United Kingdom (Parkin, 2011), Australia (Pandeya et al., 2015) and globally (Reitsma et al., 2017) have estimated the burden of cancer attributable to smoking tobacco. In addition, previous estimates for Canada and the provinces of Ontario and Alberta estimated that 15–16% of cancer is attributable to tobacco smoking (Cancer Care Ontario, 2014; Krueger et al., 2016; Poirier et al., 2016). However, current detailed estimates for Canada and individual provinces are not available. Previous studies did not estimate the proportion of cancer that could be prevented in the future with reductions in smoking prevalence.
Given the strong, consistent relationships between active and passive tobacco smoking and the associated cancer sites, we aimed to estimate the proportion of incident cancer cases in 2015 that can be attributed to past tobacco exposure in Canada (attributable burden). We also estimated the proportion of cancers in the future (to 2042) that could potentially be prevented through the implementation of one of several intervention scenarios targeted at reducing the prevalence of active tobacco smoking and passive exposure (avoidable burden).
Section snippets
Methods
The detailed methodological framework for the current study was previously published (Brenner et al., 2018). A brief overview of the methods is included in this supplement. To estimate the attributable and avoidable burden of cancer in Canada, three measures of data were required: 1) risk estimates (i.e. relative risks, RRs) for the association between smoking and each cancer, 2) the prevalence of active tobacco smoking and passive exposure in Canada and provinces, and 3) age- and sex-specific
Prevalence of tobacco exposure
Based on results from the 2003 CCHS survey, an estimated 24.1% of Canadians were current smokers and 29.5% were former smokers (Table 2). The unadjusted prevalence of current smokers was higher for men (26.6%) than women (21.7%). This difference in rates by sex was also true for former smokers, where the prevalence was 33.3% and 25.8% for men and women, respectively. The prevalence of former smoking increased by age group ranging from 15.8% in those aged 20–34 years to 42.7% in those aged
Discussion
Our results suggest that of cancers diagnosed in 2015 associated with active tobacco smoking and passive exposure, 29.4% (32,655 cases) were attributable to active tobacco smoking and 2.7% (1408 cases) were attributable to passive tobacco exposure in never smokers. These estimates correspond to 17.5% and 0.8% of all cancers diagnosed in 2015, respectively. Of the 33,672 cancer cases attributable to tobacco exposure, more than half (18,549) were lung cancer cases. Other than cancer sites
Acknowledgments
We gratefully acknowledge the statistical work completed by Farah Khandwala. Darren Brenner was supported by a Canadian Cancer Society Capacity Development Award in Cancer Prevention and Christine Friedenreich was supported by a Health Senior Scholar Award from Alberta Innovates and an Alberta Cancer Foundation Weekend to End Women's Cancers Breast Cancer Chair.
Funding sources
This research is supported by the Canadian Cancer Society Partner Prevention Research Grant (grant #703106).
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2023, Social Science and MedicineMortality Attributable to Environmental Tobacco Smoke Exposure in Spain in 2020
2023, Archivos de BronconeumologiaImpact of tobacco control policies implementation on future lung cancer incidence in Europe: An international, population-based modeling study
2021, The Lancet Regional Health - EuropeCitation Excerpt :For six countries lacking incidence data, incidence had to be estimated based on mortality data by applying a mortality to incidence ratio, a proxy for case fatality which though partly reflects health system effectiveness [47]. Overall, our results are in line with previous national or regional studies indicating that the future burden of lung cancer in Europe could be considerably reduced by implementing evidence-based tobacco control policies [11,48-52]. We examined the association between implementation of tobacco control polices and the percentage change in smoking prevalence over time.
Projected estimates of cancer in Canada in 2022
2022, CMAJ. Canadian Medical Association JournalCitation Excerpt :Nos estimations mettent en évidence les domaines dans lesquels il faut déployer plus d’efforts. En matière de prévention primaire, étant donné l’augmentation constante de l’incidence du cancer du poumon chez les femmes avant les récentes baisses, des mesures ciblées visant à réduire la consommation de tabac chez les populations plus jeunes et chez les femmes restent nécessaires15. En outre, les taux de tabagisme sont plus élevés au sein de plusieurs populations, comme les personnes à faible revenu, celles qui vivent en milieu rural et les membres des Premières Nations, les Inuits et les Métis16.
Projected estimates of cancer in Canada in 2022
2022, CMAJCitation Excerpt :Our estimates highlight where additional efforts are needed. In terms of primary prevention, given steady rising incidence of lung cancer among females before the recent declines, targeted measures to reduce tobacco consumption among younger populations and females remains necessary.15 In addition, smoking rates are higher among several populations, such as individuals with lower income, those living in rural areas, and First Nations, Inuit and Métis people.16
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Additional members of the ComPARe Study Team: Eduardo Franco, Gerald Bronfman Department of Oncology, Division of Cancer Epidemiology and Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Québec, Canada; Will King, Department of Public Health Sciences, Queen's University, Kingston, Ontario, Canada; Paul Demers, Occupational Cancer Research Centre, Toronto, Ontario, Canada; Prithwish De, Cancer Care Ontario, Toronto, Ontario, Canada; Leah Smith, Canadian Cancer Society, Toronto, Ontario, Canada; Elizabeth Holmes, Canadian Cancer Society, Toronto, Ontario, Canada; Dylan O'Sullivan, Department of Public Health Sciences, Queen's University, Kingston, Ontario, Canada; Karena Volesky, Gerald Bronfman Department of Oncology, Division of Cancer Epidemiology and Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montréal, Québec, Canada; Zeinab El-Masri, Cancer Care Ontario, Toronto, Ontario, Canada; Robert Nuttall, Health Quality Ontario, Toronto, Ontario, Canada; Mariam El-Zein, Gerald Bronfman Department of Oncology, Division of Cancer Epidemiology McGill University, Montréal, Québec, Canada; Sheila Bouten, Department of Oncology, McGill University, Montréal, Québec, Canada; Tasha Narain, Department of Public Health Sciences, Queen's University, Kingston, Ontario, Canada; Priyanka Gogna, Department of Public Health Sciences, Queen's University, Kingston, Ontario, Canada.