Glutathione S-transferase theta 1 (GSTT1) deletion polymorphism and susceptibility to head and neck carcinoma according to 107 articles: A systematic review with five analyses

Abstract GSTT1 enzyme plays a key role in the neutralization of electrophilic compounds such as carcinogens. Herein, we aimed to evaluate GSTT1 deletion polymorphism and susceptibility to head and neck carcinoma (HNC) according to 107 articles in a systematic review with five analyses. The databases of PubMed/Medline, Web of Science, Scopus, and Cochrane Library until June 21, 2023, with no restrictions to identify pertinent articles. The quality scoring was done using the Newcastle-Ottawa Scale (NOS) tool. The Review Manager 5.3 software was used to calculate the effect sizes, which were displayed as the odds ratio (OR) along with a 95% confidence interval (CI). Both the publication bias and sensitivity analyses were performed using the Comprehensive Meta-Analysis version 3.0 software. To mitigate the risk of false-positive or negative conclusions from meta-analyses, a trial sequential analysis (TSA) was conducted using TSA software.: Of 1966 records retrieved from four databases, 107 full-text articles were included in the analysis. The combined analysis revealed that the pooled OR was 1.28 (95% CI: 1.14 to 1.44; p-value < 0.0001). In terms of ethnicity, the pooled OR was highest in mixed ethnicities. For cancer type, nasopharyngeal cancer had the highest OR. When considering sample size, studies with less than 200 samples had a higher OR compared to those with 200 or more samples. The control source did not significantly affect the OR. The studies with a quality score of 7 or more had a higher OR compared to those with a score less than 7. When both age and sex are considered, while the OR of 1.42 is significant, the high heterogeneity suggests caution in interpreting these results. Finally, in the group where neither age nor sex was considered, no significant association was found. The p-values for both Egger’s test (0.904) and Begg’s test (0.237) are greater than 0.10. TSA reported that the study does not have sufficient statistical power. This comprehensive meta-analysis revealed a significant association between the GSTT1 null genotype and an increased risk of HNC, with variations based on factors such as ethnicity, cancer type, sample size, control source, and quality score.