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It is unclear whether diabetes and glycemic control affects the outcomes of breast cancer, especially amongst those with metastatic disease. This study aims to determine the impact of diabetes and hyperglycemia on cancer progression and mortality in individuals with metastatic breast cancer (MBC). Patients with a diagnosis of MBC between 2010-2021 were identified using the MBC database at two academic institutions. We evaluated the effects of diabetes and glycemic control on overall survival (OS) and time to next treatment (TTNT). We compared 244 patients with diabetes (median age 57.6 years) to 244 patients without diabetes (matched for age, sex, ethnicity and receptor subtype). OS at 5-years (diabetes: 54%, 95% CI; 47-62% vs. controls: 56%, 95% CI; 49-63%, p=0.65) and TTNT at 1-year (diabetes: 43%, CI; 36-50% vs. controls: 44%, CI; 36-51%, p=0.33) were similar between groups. A subgroup analysis comparing those with good and poor glycemic control amongst patients with specific receptor subtype profiles, showed no differences in OS at 5-years, or TTNT at 1-year. In an 8-year landmark subgroup analysis, there was worse OS amongst individuals with diabetes compared to controls, and OS was found to be better amongst those with good glycemic control compared to those with poor control. Diabetes was not associated with increased mortality in individuals with MBC at 5-years. However, diabetes and hyperglycemia were associated with worse OS amongst a cohort of longer-term survivors. These findings suggest that individualized diabetes and glycemic goals should be considered in patients with MBC. |
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