Impact of insulin use on outcomes of diabetic breast cancer patients: a systematic review and meta-analysis

OBJECTIVE: The study aimed to assess the impact of insulin use on outcomes of breast cancer patients with diabetes mellitus (DM). MATERIALS AND METHODS: Databases of PubMed, Embase, and CENTRAL were searched to identify all types of studies comparing mortality or recurrence between insulin and non-insulin DM patients with breast cancer. Adjusted hazard ratios (HR) were pooled for a meta-analysis. RESULTS: Eleven studies were included. Meta-analysis indicated a statistically significant increased risk of all-cause mortality in insulin users as compared to non-users (HR: 1.52 95% CI: 1.23 to 1.86 I-2=83% p<0.0001). Our results also demonstrated a statistically significant increase in the risk of breast cancer mortality amongst insulin users as compared to non-users (HR: 1.33 95% Cl: 1.08 to 1.63 I-2=43% p=0.007). Only four studies assessed the impact of insulin therapy on recurrence rates. Meta-analysis indicated a statistically significant increased risk of breast cancer recurrence in insulin users vs. non-users (HR: 1.43 95% Cl: 1.13 to 1.80 I-2=0% p=0.003). Mortality results were stable on sensitivity analysis. CONCLUSIONS: Diabetic breast cancer patients on insulin have increased mortality and recurrence rates as compared to insulin non-users. Owing to the several limitations of the review. results should be interpreted with caution. Future studies should assess the impact of timing, duration, dosage. and type of insulin therapy on clinical outcomes.