Background: Tobacco exposure is one of the leading risk factors for cancer. However, cancer burden attributable to tobacco is often estimated for individual countries, few specific cancer sites, or single tobacco exposures, rather than across multiple tobacco exposures.
Objectives: This study aimed to estimate the cancer burden attributable to multiple tobacco exposures, including tobacco smoking, smokeless tobacco use, and secondhand smoke (SHS) exposure across 25 Asian countries.
Methods: We estimated population attributable fractions (PAFs) using country- and sex-specific prevalence of tobacco exposures (tobacco smoking, smokeless tobacco use, and SHS) from the WHO STEPwise Approach to Surveillance (STEPS) surveys and relative risks for established causal associations with specific cancer sites. Incident case counts for 15 cancer sites in 25 Asian countries were obtained from GLOBOCAN 2022. For SHS, we estimated lung cancer incident cases among never smokers. For each tobacco exposure, the number of attributable cancer cases was calculated by multiplying the sex-specific number of incident cases (overall or restricted to never smokers for SHS) by the corresponding PAF.
Results: For the combined PAFs across 25 countries, 28.0% (men: 43.4%, women: 4.8%) of incident cancers were attributable to the tobacco smoking, estimating 106,894 of 381,921 cases. Smokeless tobacco accounted for 35.3% (men: 37.8%, women: 29.2%) of incident cancer cases, estimating 34,927 of 98,959 cases. Additionally, 16.8% (men: 14.5%, women: 17.9%) of lung cancer cases among never smokers were attributable to SHS, estimating 2,507 of 14,955 cases.
The cancer PAFs attributable to tobacco smoking ranged from 7.6% for colorectal cancer (1,800 of 23,672 cases) to 72.8% for lung cancer (30,069 of 41,323 cases) among men, and from 0.7% for ovarian cancer (99 of 15,015 cases) to 16.9% for lung cancer (2,537 of 15,036 cases) and laryngeal cancer (304 of 1,799 cases) among women. The cancer PAFs attributable to smokeless tobacco ranged from 8.3% for pancreatic cancer (371 of 4,474 cases) to 52.7% for oral cavity cancer (12,863 of 24,400 cases) among men, and from 5.2% for pancreatic cancer (135 of 2,575 cases) to 43.8% for oral cavity cancer (4,685 of 10,706 cases) among women.
At country level, the tobacco exposure-attributable fraction estimates for cancers ranged from 9.25% (men: 17.32%, women: 0.47%) in Turkmenistan (263 of 2,848 cases) to 48.64% (men: 67.22%, women: 18.66%) in Bangladesh (42,566 of 87,509 cases). The three countries with the largest numbers of incident cases attributable to tobacco exposures in both men and women were Bangladesh (men: 36,318 cases, PAF in men: 67.22%; women: 6,248 cases, PAF in women: 18.66%), Vietnam (men: 23,934 cases, PAF in men: 41.41%; women: 1,169 cases, PAF in women: 4.14%), and Pakistan (men: 16,761 cases, PAF in men: 44.89%; women: 3,530 cases, PAF in women: 12.00%).
Conclusions/Implication: Tobacco use and secondhand smoke exposure accounted for a heavy cancer burden across Asian countries. Integrating cancer control measures together with strengthening comprehensive tobacco control policies is crucial to preventing the cancer burden.