Opium Use and Risk of Lower Gastrointestinal Cancers: PopulationBased CaseControl Study in South of Iran

Background: Colorectal cancers, including colon, rectum and anus, are relatively prevalent in Iran. Use of opium and its derivatives is also considerably prevalent in some areas in Iran. Objectives: The aim of this study was to assess the association between use of opium and its derivatives, and incidence of lower gastrointestinal (LGI) cancers. Methods: This study was a matched case-control study in Shiraz (south of Iran). Cases were the new colorectal cancers from cancer registry center of Shiraz University of Medical Sciences and controls were selected from healthy volunteers of cases’ neighbors matched for age and gender (2 controls per 1 case). Data related to consumption of opium and its derivatives, smoking, alcohol use and diet status were collected through a structured questionnaire. The conditional logistic regression models were used to assess all associations. Results: 160 cases and 320 controls participated in the present study with non-response rate less than 9 %. Opium use was associated with increased risk of colorectal cancer (adjusted OR = 4.4; 95% CI: 2.2 - 8.8). Also, a dose-response association was observed between cumulative consumption of opium and the colorectal cancer incidence (OR = 3.8; 95% CI: 1.5 - 9.1), and (OR = 4.6; 95% CI: 1.7 - 12.0) for low and high use, respectively. Also, the significant dose-response association was observed for low (OR = 3.4; 95% CI: 1.2 - 9.2) and high (OR = 7.7; 95% CI: 1.5 - 38.6) opium use with presence of colon cancer. Conclusions: The results of this study showed that opium use can be an important risk factor for colorectal cancer in Iran.