Effect of Diabetes on Perioperative Colorectal Cancer Surgery Outcomes

There are conflicting study results regarding the effect of diabetes on the outcomes of colorectal cancer patients. In a study published in PLOS One, investigators found that the effects of diabetes alone on perioperative colorectal cancer surgery outcomes are overstated.

For the study, investigators analyzed data from the Cabrini Monash University Depart of Surgery colorectal neoplasia database. Patients included in the study were in the database between January 2010 and April 2015, and had undergone resection of colorectal neoplasia.

The follow-up length ranged from a little over 5 years for patients undergoing surgery in January 2010 to 3 months for patients from April 2015, according to the study. The investigators hypothesized that patients with diabetes would have poor perioperative outcomes, and that diabetes was an independent risk factor for both 30-day mortality and perioperative morbidity.

The investigators compared patients with diabetes to patients without diabetes on a range of perioperative outcomes, and used the Pearson’s χ-squared tests and t-tests to assess the differences between the groups.

Confounding factors were controlled for by separate logistic and linear regression analyses, according to the study. The Huber-White Sandwich Estimator was used to calculate robust standard errors.

In the study period, a total of 1725 patients were analyzed over 1745 treatment episodes. Of the total study cohort, 267 patients had diabetes (268 surgical episodes), while 49 of the patients had 1 or more diabetes-related complication. There were 20 patients who had metachronous cancers.

The results of the univariate analysis showed that diabetes was associated with a significant increased risk of medical complications (OR 1.67, CI 95% 1.13-2.46) and surgical complications (OR 1.45 CI 95% 1.05-1.99), as well as an increased length of stay (1.53 days, CI 95% 0.21-2.75).

The investigators used a multivariable analysis adjusted for variables that were independently associated with each outcome. They found that diabetes was an independent contributor to an increased risk of surgical complications, with no significant effect on medical complications, returns to the operating room, 30-day mortality, or readmission within 30 days.

A further analysis was conducted based on patients with diabetes, with and without diabetic-related complications. The presence of diabetic-related complications was significantly associated with an increased 30-day mortality days (95% CI 0.7—7.1), according to the study.

Although there was a trend to increased medical and surgical complications, as well as an increased rate of return to the operating room, the results were not significant.

Some limitations to the study were that the numbers involved did not match some of the administrative-coding based studies that were previously published, meaning it may underestimate any clinical effect of diabetes; the diagnosis of diabetic complications and severity were based on clinical data instead of laboratory data, such as fasting glucose levels or HbA1c; the data was derived from 2 tertiary level hospitals; and the number of patients with type 1 diabetes in the study was low, despite a significant number of patients who were classified as insulin-requiring type 2 diabetes patients.

The authors concluded that where overall baseline morbidity and mortality levels are low, the effect of diabetes alone on perioperative surgical outcomes was found to be overstated with control of associated perioperative risk factors, such as cardiac, renal, and respiratory factors being more important.