Is diabetes mellitus a risk factor for all-cause and cardiovascular mortality among breast cancer patients?

Abstract

Type 2 diabetes mellitus (DM) is a known cardiovascular disease (CVD) risk factor that is also associated with an increased risk of breast cancer (BC) and a poorer prognosis according to recent studies. The aim of our study was to assess the impact of DM on all cause, cancer-specific, CVD-related and kidney disease mortality in BC patients. This retrospective study included 2284 female BC survivors recruited from the registry of the cardio-oncology unit of Casablanca, who were diagnosed with primary non-metastatic invasive BC between 2014 and 2021 and an age-matched comparison group without BC. We estimated multivariable-adjusted hazard ratios (HRs) for mortality rates with 95% confidence intervals (CI). Among BC patients ( n = 2284), over a median follow-up of 8 years, we estimated all-cause deaths, cancer and CVD deaths respectively to 165, 43 and 38. When comparing mortality in women with and without breast cancer, we found that DM was associated with: all-cause mortality (HR: 1.41; 95% CI: 1.13–2.05 versus 1.77; 1.36–2.12) ( P = 0.073) in controls; cancer-specific mortality (HR: 1.64; 95% CI: 1.03–2.78 versus 2.12; 1,17–3,27) ( P = 0.19), and CVD-specific mortality (HR: 1.54; 95% CI: 1.12–1.83 versus 1.83; 0.97–3.72) ( P = 0.039) and kidney disease mortality (HR: 2.11; 95% CI: 1.65–2.72 versus 1.76; 1.19–3.31). Our study showed a positive association between history of physician-diagnosed DM and risk of CVD-related mortality as well as kidney disease mortality in BC patients compared to women without BC. However, BC survivors with DM had similar risk of all-cause and cancer-specific mortality during the study period. Greater attention on diabetes management is recommended in BC survivors with diabetes, especially if associated with other CVD risk factors.