Opium as a risk factor for upper gastrointestinal cancers: a population-based case-control study in Iran.

BACKGROUND Gastrointestinal cancers, including esophageal, gastric, liver and pancreatic are relatively common in Iran. Furthermore, consumption of opium and its derivatives (O&D) are considerable. This study, aimed to examine the association between consumption of O&D and the incidence of upper gastrointestinal (UGI) cancers. METHODS In a matched case-control study in Kerman (located in southeast of Iran), 142 patients with UGI cancers and 284 healthy people (matched in terms of age, sex and residence (urban/rural)) were recruited. Variables (using O&D, smoking, alcohol use and diet) were collected using a structured questionnaire. Conditional logistic regression models were used to assess the above mentioned association. RESULTS Opium use was associated with an increased risk of UGI cancers with an adjusted OR 4.0 (95% CI=2.2-7.0). A very strong dose-response relation was observed between consumption of O&D and the incidence of UGI cancers. (Three consumption levels-none, low and high; OR=18.7; 95% CI=5.5-63.3). This dose-response relationship was also strong even in patients with gastric cancers (OR=9.2; 95% CI=2.5-33.7). CONCLUSION The results of this study showed that opium consumption can be a strong risk factor for UGI cancers in Iran.