Opium Usage and Risk of Head and Neck Cancer: A Systematic Review and Meta-Analysis

INTRODUCTION: Opium is among the most used substance of abuse worldwide. More than 50 million opium users are there worldwide, majority of whom are in Asia. Opium usage have been reported to be associated with cancer. This study aimed to find the association between opium use or abuse and head and neck cancer. METHODS: A systematic search was conducted in Medline, Scopus, Cochrane, and Google Scholar database for studies published from inception till 1(st) November 2019. Two authors independently reviewed the studies, did quality assessment, and extracted data in standardized data extraction form. Pooled estimate of OR for risk of head and neck cancer was calculated using random effects model using the method of DerSimonian and Laird, with the estimate of heterogeneity being taken from the inverse-variance model. Subgroup and sensitivity analysis were performed. The protocol was registered in PROSPERO (CRD42020156049). RESULTS: Fourteen studies were included in data synthesis (11 case control studies and 3 cohort studies). Eleven case control studies were included in synthesizing the results for meta-analysis. Pooled odds ratio for risk of cancer among opium users for the 11-case control study was 3.85 (2.18-6.79). Heterogeneity was high (I-squared=92.0%, Tau-squared=0.88). There was no publication bias in the study. Subgroup analysis showed highest OR for pooled estimate for risk of laryngeal cancer (19.98 (11.04-36.15)). CONCLUSION: There was almost four-fold rise in risk of head and neck cancer among opium users compared to non-users.