Enhancing the Efficacy of Metformin in Neoadjuvant Therapy for Breast Cancer: A Meta-Analysis Based on Randomized Clinical Trials

Introduction This meta-analysis aims to evaluate the impact of increasing the use of metformin in neoadjuvant treatment for breast cancer (BC) on the rate of pathological complete response (pCR) in patients. Methods A systematic search was conducted in four electronic databases: PubMed, Web of Science, Embase, and Cochrane Library. The search scope covered all the literature from the establishment of the databases to April 2025. The risk ratio (RR) and 95% confidence interval (CI) were calculated. The outcome indicator was the pCR rate. Result This meta-analysis included a total of 8 randomized controlled trials (RCTs), involving 474 patients. The results showed that there was no statistically significant difference in the pCR rate between the experimental group containing metformin and the control group (RR = 1.21, 95% CI: [0.85, 1.71], P = 0.28). Subgroup analysis revealed that there were no significant differences in the pCR rate between the two groups in patients with metabolic syndrome (RR = 2.09, 95% CI [0.55, 7.85], P = 0.28), patients without metabolic syndrome (RR = 1.12, 95% CI [0.81, 1.55], P = 0.49), patients from Eastern countries (RR = 1.15, 95% CI [0.63, 2.11], P = 0.65), and patients from Western countries (RR = 1.32, 95% CI [0.75, 2.32], P = 0.34). Conclusion This study did not observe any effect of increasing the use of metformin on the pCR rate of patients in neoadjuvant treatment for BC.