ABSTRACT
Objective To evaluate the efficacy and security of metformin in the treatment of endocrine resistance and postmenopausal hormone receptor positive advanced breast cancer. Methods 60 cases of postmenopausal HR+advanced breast cancer whose first-line or second-line endocrine therapy failed were randomly divided into study group(n=30),treated with metformin combined with AI and control group(n=30),treated with placebo combined with AI. Standard RECIST guidelines were used to evaluate the clinical response. The objective response rate(ORR),clinical benefit rate(CBR),progression-free survival,and adverse reactions of two groups were compared. Results The ORR of two groups were 16.7%and 10%respectively and the difference was not statistically significant(P > 0.05). But CBR in study group was significantly higher than that in control group (63.3%vs 36.7%),and the difference was statistically significant(P<0.05). The median PFS in study group was slightly longer than that in control group (3.7 m vs 4.2 m),but there was no statistical difference. Multivariate regression analysis showed that PFS was only associated with the previous endocrine therapy. No serious adverse reactions occurred in two groups. Conclusion Metformin is expected to improve secondary endocrine resistance in breast cancer,but large prospective clinical studies are needed to confirm it.