Diabetes Drug May Improve Survival in Patients With Ovarian Cancer

Sanjeev Kumar, MBBS

The oral diabetic medication metformin may help improve survival in patients with ovarian cancer, according to the results of a retrospective case-control study from the Mayo Clinic in Rochester, Minnesota.

Previous studies have shown promise for metformin as an anticancer compound. For this study, researchers used Mayo Clinic hospital records to identify patients with ovarian cancer who also received metformin for a minimum of 1 year at or after their cancer diagnosis (mean duration = 2.3 years; range, 1-11 years). Duration of metformin therapy prior to their cancer diagnosis was unknown.

The study’s ovarian cancer cohort comprised women with ovarian cancer who were also taking metformin (n = 72) and a randomly selected control group of patients with ovarian cancer who did not receive metformin (n = 143). Median disease-specific survival (DSS) for the entire group was 5.5 years. For the control group, the 5-year survival rate was 44%, whereas the survival rate for patients on metformin was 73% (P = .002).

Because epithelial ovarian cancer (EOC) accounts for most ovarian cancer mortality, the researchers identified a subset of patients with EOC from the initial cohort who had received metformin (n = 61) and compared these cases with a control group of patients with ovarian cancer who had not received metformin (n =178). Variables such as age, disease stage, histology, and receipt of platinum- versus non-platinum—based chemotherapy were similar between the two groups, which together comprised the EOC cohort (N = 239).

For the entire EOC cohort, the 5-year DSS rate was 52%. For the subset of EOC cases taking metformin, the DSS rate was significantly better than DSS in the control group: 67% versus 47%, respectively (P = .006). The researchers found that metformin was an independent predictor of survival, even after adjusting for body mass index, tumor grade, histology, surgical cytoreduction, disease stage, and chemotherapy (hazard ratio = 2.2; 95% CI, 1.2-3.8; P = .007).

When the EOC cohort was compared with a diabetic control group of patients with EOC whose diabetes was being treated with insulin or medications other than metformin (n = 103), 5-year DSS was lower for the diabetic control group (40%) as compared with the EOC cohort and nondiabetic controls. In this analysis, researchers also looked at 5-year DSS associated with specific antidiabetic medications. Metformin use was associated with a higher DSS rate (67%) than insulin (43%) and other antidiabetic medications (34%; P = .004).

The researchers noted that their findings are consistent with an earlier University of Chicago study reported in the January 2012 issue of Obstetrics & Gynecology, which found an association between metformin and improved recurrence-free survival in patients with ovarian cancer.

“Our study demonstrated improved survival in women with ovarian cancer who were also taking metformin,” co-lead author Sanjeev Kumar, MBBS, a fellow in Gynecologic Oncology at the Mayo Clinic, said in a statement. “Although causation could not be assessed by our retrospective study, metformin nevertheless is a strong contender for further clinical studies in ovarian cancer,” the researchers concluded.

Kumar S, Meuter A, Thapa P, et al. Metformin intake is associated with better survival in ovarian cancer [published online ahead of print December 3, 2012]. Cancer. doi:10.1002/cncr.27706.