April 8, 2010 — Newly diagnosed cancer patients, particularly those with colorectal or esophageal tumors, are 50% more likely to die after surgery if they have type?2 diabetes than if they do not, researchers report in the April issue of Diabetes Care.
Researchers, led by Bethany B. Barone, ScM, from the Department of Epidemiology, Johns Hopkins School of Public Health in Baltimore, Maryland, conducted a systematic review and meta-analysis of short-term postoperative mortality after initial cancer treatment. They identified 8828 prospective articles, of which 20 met the inclusion criteria for qualitative systematic review.
Fifteen studies, ranging in size from 70 to 32,621 patients (median, 427 patients), reported sufficient information to be combined in a meta-analysis. This showed that preexisting diabetes was associated with a 51% greater risk for short-term postoperative mortality in cancer patients, even after confounders and publication bias were accounted for.
Preexisting diabetes was associated with increased odds of postoperative mortality across all cancer types (odds ratio, 1.85, 95% confidence interval, 1.40?- 2.45), the authors report.
"Diabetic patients, their oncologists, and their surgeons should be aware of the increased risk when they have cancer surgery," said coauthor Hsien-Chieh "Jessica" Yeh, PhD, assistant professor of general internal medicine and epidemiology at the Johns Hopkins University School of Medicine.
"Care of diabetes before, during, and after surgery is very important. It should be part of the preoperative discussion," she said in a statement.
How Is Risk Increased?
Senior author Frederick L. Brancati, MD, told Medscape Oncology that this study and a recent meta-analysis that showed a 40% increased risk for death in the long-term (JAMA. 2008 17;300:2754-2764) both raise the question of timing.
"Was it just diabetes leading to cardiovascular risk 'on its own,' independent of cancer? This study of short-term mortality postop indicates that there's immediate risk, related in time to cancer treatment," said Dr. Brancati, chief of the Division of General Internal Medicine at Johns Hopkins School of Medicine.
In the current paper, the researchers suggest 2 ways that preexisting diabetes might influence postoperative mortality risk after cancer surgery: sepsis or other serious infections (with risk heightened by perioperative hyperglycemia), and myocardial infarction.
"Diabetes is a chronic risk factor for atherosclerosis in multiple vascular beds, including the coronary arteries, and is a strong predictor of myocardial infarction and cardiovascular disease death in the general population," they write.
This study has several limitations, the authors note, including "great heterogeneity in population demographics and in assessment of confounders."
The researchers found no studies evaluating the effect of diabetes on postoperative mortality in women with breast or endometrial cancer and, therefore, say they "are uncertain whether our findings apply to women with these cancers."
"Overall mortality is lower for these cancers, so it's harder to 'find the signal.' Therefore, researchers don't look there," Dr. Brancati explained.
Finally, the researchers were not able to compare the effect of diabetes on short-term survival in cancer patients who did and who did not undergo surgery. "This gap may be especially important because diabetes is known to influence treatment decisions and might steer some patients toward nonsurgical treatment," the authors write.
The analysis raises the question of whether better perioperative diabetes care would reduce the risk for postoperative mortality after cancer surgery, but the authors note that randomized controlled trials of intensive insulin therapy in surgical intensive care units "have yielded mixed results."
"The main implication of our study is that oncologists, surgeons, and cancer patients should be aware of the excess postoperative mortality risk related to diabetes when considering treatment options. Whether improvements in perioperative diabetes care can reduce this excess risk is uncertain," the authors conclude.
The researchers have disclosed no relevant financial relationships.
