Tobacco and opium use and risk of liver and colorectal cancer mortality: Analysis of the Golestan Cohort Study (GCS).

BACKGROUND: Tobacco and opium consumption are prevalent in Iran and have been linked to increased risk of upper GI cancers. To investigate their role in lower GI cancers, the associations of tobacco and opium use with liver and colorectal cancer mortality were examined in this study. METHODS: From 2004-2008, participants aged 40 to 75 years were recruited through random systematic cluster sampling and primary healthcare worker contact in Golestan, Iran. Baseline assessment of tobacco and opium use, demographic information and cancer-relative risk factors were conducted through validated questionnaires. Cancer diagnoses and deaths were collected through regular follow-up between 2004 and March 6, 2023. Multivariate Cox proportional regression model evaluated the association between tobacco and opium use and liver and colorectal cancer mortality. RESULTS: During a median 15 years of follow up, 112 participants developed liver cancer and 201 developed colorectal cancer. Cigarette smoking (hazard ratio [HR] = 1.76, 95% confidence interval [CI] 1.05, 2.94) and water-pipe smoking (HR = 3.20, 95% CI 1.12, 9.13) were associated with liver cancer. Opium was not associated with liver cancer. We observed no associations between tobacco or opium use and risk of colorectal cancer. CONCLUSIONS: Cigarette and water-pipe smoking were associated with increased liver cancer mortality, whereas no significant associations were observed for tobacco and opium use and colorectal cancer mortality. IMPACT: Tobacco control could be a strategy for reducing liver cancer mortality in high-risk populations. Larger prospective studies are required to confirm the associations of tobacco and opium use with lower GI cancers.