Impact of smoking and opium cessation on gastrointestinal cancer risk: A 15-year longitudinal study in Golestan Cohort.

Smoking and opium use are risk factors for gastrointestinal cancers, yet the extent to which cessation reduces cancer risk remains unclear, particularly in non-Western populations. This study analyzed data from the Golestan Cohort Study in northeastern Iran, comprising 50,045 adults aged 40-75 years followed for a median of 15 years. Participants were classified into never-users, current smokers or recent quitters (less than 5 years), and long-term quitters (more than 5 years). For esophageal cancer, long-term quitters demonstrated substantial risk reductions (HR for smoking: 0.68; 95% CI: 0.47-0.99; HR for opium: 0.33; 95% CI: 0.12-0.90), while current users and recent quitters of both smoking and opium indicated increased risks (HR for smoking: 1.53; 95% CI: 1.14-2.07; HR for opium: 1.50; 95% CI: 1.20-1.88). For stomach cancer, long-term smoking quitters showed a protective effect, with a 35% risk reduction though no significant risk reduction was observed for long-term opium cessation. For pancreatic cancer no significant risk reduction was noted among long-term quitters. This study highlights that cessation of smoking or opium use for more than 5 years can reduce the risk of esophageal cancer, while risk reduction for other types of gastrointestinal cancers requires longer cessation duration.