Can Opium Use Contribute to a Higher Risk of Colorectal Cancers? A Matched Case-control Study in Iran

BACKGROUND Colorectal cancers (CRCs) including colon, rectum and anal cancers are the third most prevalent cancers in the world. There are strong evidence showing the risk of the cigarette smoking, alcohol use, low physical activity and some types of diets in CRCs; however, few studies explored the relationship between opium use and CRCs. This study aimed to investigate the association between opioid use and the incidence of CRCs. METHODS In a population-based matched case-control study in Kerman, Iran, 175 patients with colorectal cancers and 350 healthy controls (matched for age, sex, and place of residence) were interviewed from Sep 2014 to Nov 2014. Opium and its derivatives, cigarette, alcohol, and diet use were collected using a valid and reliable questionnaire. Conditional logistic regression was used to estimate odds ratios with 95% confidence intervals. RESULTS The use of opioids was associated with an increased risk of CRCs (adjusted odds ratio= 4. 5, 95% CI: 2. 4-8. 7). In addition, a dose-response relationship was observed between the cumulative use of opioids and the incidence of CRCs (with low use OR=3. 7; 95% CI: 1. 5-8. 6 and high use OR= 8. 0; 95% CI: 2. 9-21. 7). This dose-response relationship was also strong in patients with colon cancers, with OR= 3. 9 (95% CI: 1. 5-9. 9) and 9. 4 (95% CI: 3. 3-27. 0) for the low and high uses of opioids, respectively. CONCLUSION Opioid use can lead to an increased risk of CRCs. Therefore, it is necessary to implement preventive policies to control the use of opioids.