Pre-existing diabetes associated with all-cause mortality in breast cancer
Diabetes increases the risk for death from any cause by nearly 50% in patients with breast cancer, according to results of a systematic review and meta-analysis. In addition, patients with both breast cancer and pre-existing diabetes are more likely to present with later-stage disease and to receive altered treatment regimens.
However, the researchers cautioned that “although all-cause mortality was increased in patients with breast cancer and diabetes, the association between breast cancer-specific mortality and diabetes is not clear.”
Researchers identified 8,828 studies on diabetes and the prognostic outcomes of breast cancer using the EMBASE and MEDLINE databases. Eight articles were included in the study because each reported prognostic outcomes by diabetes status, evaluated a cancer population and contained original data published in English, according to the researchers.
Six studies reported a risk estimate for diabetes and the link to all-cause mortality. Pooled results from these studies demonstrated that pre-existing diabetes was associated with a 49% increased risk for all-cause mortality in women with breast cancer (HR=1.49; 95% CI, 1.35-1.65).
Three of four studies examining the relationship between pre-existing diabetes and breast cancer stage reported a positive association. According to results from Fleming et al, women with diabetes had a higher risk for late-stage breast cancer (OR=1.17; 95% CI, 1.08-1.27). Results from Srokowski et al demonstrated that more women with diabetes were diagnosed with a more advanced stage compared with patients without diabetes (47% vs. 42% stage 2 or 3; P<.0001). Lastly, van de Poll-Franse et al found that patients with diabetes and breast cancer were more likely to be diagnosed with stage 3 or 4 disease (19% vs. 12%). However, the fourth study by Yancik et al reported no association between diabetes status and disease stage.
Pre-existing diabetes was also associated with altered treatment regimens and an increased risk for hospitalization due to chemotherapy toxicity. One study reported a negative association between diabetes and disease-free survival in black and white women with stage 1, 2 or 3 disease (HR=1.81; 95% CI, 1.03-3.18).
“The main implication of our study is that diabetes is associated with adverse outcomes in breast cancer throughout its full course, from initial presentation, during treatment (affecting the choice of treatment), and, ultimately, to mortality,” the researchers wrote. “Diabetes therefore deserves additional attention to assess possible causal relationships that potentially could be modified to improve outcomes.”
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