Diabetes Drug May Be Effective Treating Cancer

Metformin found to improve survival in breast cancer and shows promise in endometrial hyperplasia.

A commonly used type 2 diabetes drug improved survival in breast cancer patients and shows promise as a potential treatment for endometrial hyperplasia.

Metformin is an oral drug typically used as first-line treatment for type 2 diabetes to help control blood sugar levels and showed promise in recent studies. Findings from 2 new studies were presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago.

ASCO abstract 1569 was the first to examine the effect of metformin on breast cancer patient survival rates. Clinical outcomes were examined in 1215 breast cancer patients who underwent surgery between 1997 and 2013.

There were 97 patients who reported using metformin before they were diagnosed and 97 who used it after diagnosis.

The results of the study showed that patients who used metformin before their diagnosis were more than twice as likely to die as patients who never used metformin. Furthermore, breast cancer patients that took metformin after their diagnosis were 50% more likely to survive than non-users.

“Using metformin as a cancer prevention strategy has been controversial and results have been inconsistent, but our analysis reveals that use of the drug is time-dependent, which may explain the disparity,” said lead study author Yun Rose Li, MD, PhD. “While use of the drug may have a survival benefit for some breast cancer patients, those who developed breast cancer while already using Metformin may have more aggressive cancer subtypes.

“Our study also illustrates the complex interaction between underlying metabolic risks and breast cancer outcomes, and underscore the importance of a multi-system approach to cancer treatment.”

Upon further analysis, African Americans the age of 50 were more likely to use metformin.

The tumor size and progression was found similar among the groups, however, patients who used the drug after their diagnosis were more likely to have ER/PR positive tumors. Patients who used metformin before their diagnosis showed higher rates of Her2+ and triple negative tumors.

Authors note that further researcher needs to be done to examine the impact of metformin on cancer recurrence, but the findings do suggest that the differences in breast cancer tumor markers could be due to mechanistic differences in cancer initiation in patients who are taking metformin and develop cancer.

For ASCO abstract 5592, researchers studied the efficacy of metformin in women with newly diagnosed endometrial hyperplasia. Researchers enrolled 18 patients in the multi-institutional trial who were given metformin for 3 months.

The results of the study showed that 56% of patients responded to treatment, which researchers defined as a complete resolution of hyperplasia. The effect was most substantial in women with simple hyperplasia, who didn’t have any additional irregularities or complications.

“The results of our study may present an alternative treatment for particular forms of endometrial hyperplasia, in contrast to standard progesterone-based therapies or hysterectomy,” said lead study author Emily Ko, MD, MSCR. “Future prospective studies may better identify women for which metformin may be most beneficial, as well as the most effective dosing regimens.”