Predictive validity of American College of Surgeons: National Surgical Quality Improvement Project risk calculator in patients with ovarian cancer undergoing interval debulking surgery.

INTRODUCTION

In gynecologic patients, few studies describe the accuracy of the American College of Surgeons-National Surgical Quality Improvement Project (ACS-NSQIP) pre-operative risk calculator for women undergoing surgery for ovarian cancer.

OBJECTIVE

To determine whether the ACS-NSQIP risk calculator accurately predicts post-operative complications and length of stay in patients undergoing interval debulking surgery for advanced stage epithelial ovarian cancer.

METHODS

For this multi-institutional retrospective cohort study, pre-operative risk factors, post-operative complication rates, and Current Procedural Terminology codes were abstracted from records of patients with ovarian cancer managed with open interval debulking surgery from January 2010 to July 2015. A power calculation was done to estimate the minimum number of complications needed to evaluate the accuracy of the ACS-NSQIP risk calculator. Predicted risk compared with observed risk was calculated using logistic regression. The predictive accuracy of the ACS-NSQIP risk calculator in estimating post-operative complications or length of stay was assessed using c-statistics and Briar scores. Complications with a c-statistic of >0.70 and Brier score of <0.01 were considered to have high discriminative ability.

RESULTS

A total of 261 patients underwent interval debulking surgery, encompassing 21 unique Current Procedural Terminology codes. Readmission (n=25), surgical site infection (n=35), urinary tract infection (n=12), and serious post-operative complications (n=57) met the minimum event threshold (n>10). All predicted complication rates fell within the IQR of the observed incidence rates. However, the ACS-NSQIP calculator demonstrated neither discriminative ability nor accuracy for any post-operative complications based on c-statistics and Brier scores. The calculator accurately predicted length of stay within 1 day for only 32% of patients and could not accurately predict which patients were likely to have a prolonged length of stay (c-statistic=0.65).

CONCLUSION

Among patients undergoing interval debulking surgery, the ACS-NSQIP did not accurately discriminate which patients were at increased risk of complications or extended length of stay. The risk calculator should be considered to have limited utility in informing pre-operative counseling or surgical planning.