Background: Metformin has been associated with improved survival outcomes in various malignancies.
However, observational studies in head and neck cancer are inconsistent.
Objective: The study aimed to summarize and quantify the relationship between metformin use and the survival
of head and neck cancer.
Methods: A meta-analysis based on cohort studies was systematically conducted (published up to Jan 18, 2020),
identified from PubMed, Embase, Web of Science, Cochrane Library, Google Scholar, and Scopus databases.
Summary hazard ratios (HR) and 95% confidence intervals (CI) were calculated using a random-effects model.
Results: Seven retrospective cohort studies including 3,285 head and neck cancer patients were included. The
association between the use of metformin and cancer survival was not statistically significant: summarized HR of
0.89 (95% CI 0.66-1.18, P=0.413, I2=64.0%) for overall survival, summarized HR of 0.65 (95% CI 0.31-1.35,
P=0.246, I2=60.3%) for disease-free survival, and summarized HR of 0.69 (95% CI 0.40-1.20, P=0.191,
I2=73.1%) for disease-specific survival.
Conclusion: In this meta-analysis of 7 retrospective cohort studies, there was not a statistically significant association
between the use of metformin and better survival for head and neck cancer. However, the analysis may
have been underpowered. More studies of prospective designs with larger sample sizes are needed to investigate
the effect of metformin on the survival of head and neck cancer.