By using the Surveillance, Epidemiology, and End Results-Medicare database, we identified patients aged 66 years or older who had stages I through III
breast cancer that was diagnosed between 1992 and 2002. Multivariable regression analyses were performed to determine the effect of diabetes on use of
chemotherapy, toxicities, and outcomes. The risks of all-cause mortality and
breast cancer-specific (BCS) mortality were estimated with the Kaplan-Meier method.
RESULTS: Our cohort had 70,781 men and women, of whom 14,414 (20.36%) had diabetes. Among people who received
chemotherapy (n = 11,826), 21.0% were diabetics. In this group, diabetics had lower odds of receiving
anthracyclines (odds ratio [OR], 0.78; 95% CI, 0.71 to 0.87) and
taxanes (OR, 0.86; 95% CI, 0.75 to 0.99). Diabetes was associated with increased odds of being hospitalized for any
chemotherapy toxicity (OR, 1.38; 95% CI, 1.23 to 1.56), for
infection or
fever (OR, 1.43; 95% CI, 1.2 to 1.7), for
neutropenia (OR, 1.22; 95% CI, 1.03 to 1.45), for
anemia (OR, 1.24; 95% CI, 1.05 to 1.47), and for any cause (OR, 1.32; 95% CI, 1.19 to 1.46). Patients with diabetes had higher all-cause mortality (hazard ratio [HR], 1.35; 95% CI, 1.31 to 1.39). There was a significant interaction between diabetes and
chemotherapy use for BCS mortality. Diabetic and nondiabetic patients who did not receive
chemotherapy had similar BCS mortality, but diabetic patients who did receive
chemotherapy had higher BCS mortality than nondiabetic patients (OR, 1.20; 95% CI, 1.07 to 1.35).
CONCLUSION: In this observational, hypothesis-generating study, patients who have
breast cancer and diabetes are at increased risk of
chemotherapy-related toxicities compared with nondiabetic patients who are receiving
chemotherapy and have higher all-cause mortality.