Context Diabetes mellitus appears to be a risk factor for some cancers, but the effect of preexisting diabetes on all-cause mortality in newly diagnosed cancer patients is less clear. Objective To perform a systematic review and meta-analysis comparing overall survival in cancer patients with and without preexisting diabetes. Data Sources We searched MEDLINE and EMBASE through May 15, 2008, including references of qualifying articles. Study Selection English-language, original investigations in humans with at least 3 months of follow-up were included. Titles, abstracts, and articles were reviewed by at least 2 independent readers. Of 7858 titles identified in our original search, 48 articles met our criteria. Data Extraction One reviewer performed a full abstraction and other reviewers verified accuracy. We contacted authors and obtained additional information for 3 articles with insufficient reported data. Results Studies reporting cumulative survival rates were summarized qualitatively. Studies reporting Cox proportional hazard ratios (HRs) or Poisson relative risks were combined in a meta-analysis. A random-effects model meta-analysis of 23 articles showed that diabetes was associated with an increased mortality HR of 1.41 (95% confidence interval [CI], 1.28-1.55) compared with normoglycemic individuals across all cancer types. Subgroup analyses by type of cancer showed increased risk for cancers of the endometrium (HR, 1.76; 95% CI, 1.34-2.31), breast (HR, 1.61; 95% CI, 1.46-1.78), and colorectum (HR, 1.32; 95% CI, 1.24-1.41). Conclusions Patients diagnosed with cancer who have preexisting diabetes are at increased risk for long-term, all-cause mortality compared with those without diabetes.

A B S T R A C T PurposeThe goal of this study was to perform a systematic review and meta-analysis to examine the effect of pre-existing diabetes on breast cancer-related outcomes. MethodsWe searched EMBASE and MEDLINE databases from inception through July 1, 2009, using search terms related to diabetes mellitus, cancer, and prognostic outcome. Studies were included if they reported a prognostic outcome by diabetes status, evaluated a cancer population, and contained original data published in the English language. We performed a meta-analysis of pre-existing diabetes and its effect on all-cause mortality in patients with breast cancer and qualitatively summarized other prognostic outcomes. ResultsOf 8,828 titles identified, eight articles met inclusion/exclusion criteria and described outcomes in patients with breast cancer and diabetes. Pre-existing diabetes was significantly associated with all-cause mortality in six of seven studies. In a meta-analysis, patients with breast cancer and diabetes had a significantly higher all-cause mortality risk (pooled hazard ratio [HR], 1.49; 95% CI, 1.35 to 1.65) compared with their nondiabetic counterparts. Three of four studies found pre-existing diabetes to be associated with more advanced stage at presentation. Diabetes was also associated with altered regimens for breast cancer treatment and increased toxicity from chemotherapy. ConclusionCompared with their nondiabetic counterparts, patients with breast cancer and pre-existing diabetes have a greater risk of death and tend to present at later stages and receive altered treatment regimens. Studies are needed to investigate pathophysiologic interactions between diabetes and breast cancer and determine whether improvements in diabetes care can reduce mortality in patients with breast cancer.

Assessing glycemia in diabetes can be a challenge, but approaches are available that promote successful management of blood glucose and may thereby lead to a significant reduction in morbidity and mortality related to diabetes.