Impact of Diabetes on Patient Outcomes in Breast Cancer Patients

Abstract

Background: Diabetes and the etiology of breast cancer are clearly associated. However, the impact of diabetes on prognosis is not yet understood. Therefore, we conducted a retrospective cohort study to examine the relationship between diabetes and patient outcomes in breast cancer patients.

Methods: We investigated 332 Japanese women with breast cancer who underwent curative surgery at our hospital. Patients without sufficient clinical information including hemoglobin A1c (HbA1c) and those with an observation period of less than 1 year were excluded.

Results: Among the patients examined, 106 had diabetes at the time of their breast cancer diagnosis. Among the 296 patients with invasive breast carcinoma, 36 patients developed distant metastases during the mean observation period of 45 months. Sixteen patients died due to breast cancer, while 13 died of other causes. Multivariate analysis revealed that diabetes, tumor size, and estrogen receptor (ER) status were independent factors related to distant metastasis-free survival (DMFS) (p = 0.038, p < 0.001, and p = 0.006, respectively). Kaplan-Meier curve analysis revealed that diabetes negatively affected the outcomes of ER-negative breast cancer patients both in DMFS and overall survival (p = 0.045 and p = 0.029, respectively). Meanwhile, patient outcomes did not differ according to the level of HbA1c in diabetes patients.

Conclusion: Patients with diabetes had a significantly shorter DMFS, and the negative effect of diabetes on patient outcomes was more evident in ER-negative breast cancer. Our data indicates the importance of primary prevention of diabetes for breast cancer patients.

Keywords: Breast cancer; Diabetes; Glycemic control; Insulin resistance; Prognosis.

Fig. 1

Association between clinicopathological features and patient outcomes. Factors relating with DMFS (a) and OS (b) were analyzed employing the Cox proportional hazards model. Forest plots are also shown for HRs in the univariate analysis. BMI, body mass index; ER, estrogen receptor; PgR, progesterone receptor; HER2, human epidermal growth factor receptor 2; HR, hazard ratio; CI, confidence interval.

Fig. 2

Kaplan-Meier curves of 296 patients with invasive breast cancer according to diabetes status. Kaplan-Meier curves of DMFS (a–c) and OS (d–f) according to diabetes. The blue curve indicates patients with diabetes, and the brown curve indicates those without diabetes. Data are shown for all patients (a, d), ER-positive patients (b, e), and ER-negative patients (c, f), respectively.

Fig. 3

Patient outcomes with diabetes according to HbA1c. Kaplan-Meier curves of DMFS (a) and OS (b) according to HbA1c in patients with diabetes. The blue curve indicates patients with high HbA1c (>7.0%), and the brown curve indicates those with low HbA1c (≤7.0%).