Opium: An emerging risk factor for gastric adenocarcinoma

Opium use has been associated with higher risk of cancers of the esophagus, bladder, larynx, and lung; however, no previous study has examined its association with gastric cancer. There is also little information on the associations between hookah (water pipe) smoking or the chewing of tobacco products and the risk of gastric cancer. In a case‐control study in Golestan Province of Iran, we enrolled 309 cases of gastric adenocarcinoma (118 noncardia, 161 cardia and 30 mixed‐location adenocarcinomas) and 613 matched controls. Detailed information on long‐term use of opium, tobacco products and other covariates were collected using structured and validated lifestyle and food frequency questionnaires. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were obtained using conditional logistic regression models. Opium use was associated with an increased risk of gastric adenocarcinoma, with an adjusted OR (95% CI) of 3.1 (1.9–5.1), and this increased risk was apparent for both anatomic subsites (cardia and noncardia). There was a dose‐response effect, and individuals with the highest cumulative opium use had the strongest association (OR: 4.5; 95% CI: 2.3–8.5). We did not find a statistically significant association between the use of any of the tobacco products and risk of gastric adenocarcinoma, overall or by anatomic subsite. We showed, for the first time, an association between opium use and gastric adenocarcinoma. Given that opium use is a traditional practice in many parts of the world, these results are of public health significance. What's new? Opium use has been associated with higher rates of various cancers, and this study is the first to look at the relationship between opium use and gastric cancer risk. The authors collected information from 309 gastric cancer cases and almost twice that many age, gender and neighborhood‐matched controls about their opium use, among other lifestyle factors. Those that had ever used opium were three times more likely to have contracted gastric cancer. They found no association between gastric cancer and cigarette smoking, which is a more well‐known risk factor.