Study Links Diabetes and Worse Outcomes in Long-Term Survivors of Metastatic Breast Cancer

Women who are longer-term survivors of metastatic breast cancer may have a worse survival rate if they have diabetes and poorly controlled blood sugar levels, according to a study presented at ENDO 2022.

The authors of the study point out that a well-established relationship between diabetes and breast cancer exists, but it’s still unclear how diabetes affects breast cancer outcomes. “This study aims to determine the impact/ association of diabetes and hyperglycemia on cancer progression and mortality in individuals with metastatic breast cancer,” the authors write.

This is the first study to specifically examine the effect of blood sugar control on cancer outcomes in patients with advanced breast cancer, according to lead researcher Y.M. Melody Cheung, MD, of Brigham and Women’s Hospital, Harvard Medical School in Boston.

The researchers studied 488 patients with metastatic breast cancer – 244 with diabetes and 244 without. The study found that overall survival at five years was similar between the two groups. However, among those who survived at least eight years after their cancer diagnosis, survival for those without diabetes was better than those with diabetes (87% vs. 67% at 10 years). In these longer-term survivors, survival was also better among those with good blood sugar control compared with those with poor blood sugar control (83% vs. 63% at 10 years).

“These data provide some reassurance that hyperglycemia may not be a major contributor to overall mortality in the first 5 years, in most individuals with metastatic breast cancer,” the authors conclude. “However, amongst longer-term survivors, diabetes was associated with worse survival, suggesting that individualized diabetes and glycemic goals should, therefore, be considered in patients with metastatic breast cancer.”