More favorable progesterone receptor phenotype of breast cancer in diabetics treated with metformin.

The coexistence of type 2 diabetes with breast cancer may result in poorer cancer-related survival due to a number of mediating factors including an alteration of tumor tissue hormonal sensitivity. Previous studies have shown that receptor status of breast tumors in diabetics may be changed; however, the mode of therapy for diabetes was usually ignored. This work presents the results of an analysis of the receptor status of breast carcinomas in 90 postmenopausal women suffering with diabetes mellitus type 2 who had been cured, for not less that 1 year prior to surgery, with different modes of antidiabetic therapy, including a dietary treatment only, sulfonylurea preparations, insulin therapy, and metformin as a monotherapy or in combination with sulfonylurea derivatives. No differences in estrogen receptors occurrence in tumor tissue were found in different treatment groups. The frequency of progesterone receptor-positive mammary carcinomas in women who were treated with metformin, irrespective of whether it was combined with sulfonylurea preparations, was significantly higher than in the sulfonylurea only group (P=0.043) and in the combined group of patients treated with either sulfonylurea or insulin (P=0.041). The exclusion of the patients who received neoadjuvant chemotherapy (24 persons) did not significantly affect the above results. The data may be used as an explanation of the distinctions in cancer characteristics and course between diabetic patients treated with either metformin or sulfonylurea derivatives and insulin.