Background: For clinical decision making it is important to identify patients at risk for adverse outcomes after colorectal cancer (CRC) surgery, especially in the older population. Because the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) surgical risk calculator is potentially useful in clinical practice, we performed an external validation in a Dutch multicenter cohort of patients ≥70 years undergoing elective non-metastatic CRC surgery.
Methods: We compared the ACS NSQIP calculator mean predicted risk to the overall observed rate of anastomotic leakage, return to operation room, pneumonia, discharge not to home, and readmission in our cohort using a one-sample Z-test. Calibration plots and receiver operating characteristic (ROC) curves were used to determine the calculator's performance.
Results: Six hundred eighty-two patients were included. Median age was 76.2 years. The ACS NSQIP calculator accurately predicted the overall readmission rate (predicted: 8.6% vs. observed: 7.8%, p = 0.456), overestimated the rate of discharge not to home (predicted:11.2% vs. observed: 7.0% p = 0.005) and underestimated the observed rate of all other outcomes. The calibration plots showed poor calibration for all outcomes. The ROC-curve showed an area under the curve (AUC) of 0.75 (95% confidence interval [CI] 0.67-0.83) for pneumonia and 0.70 (0.62-0.78) for discharge not to home. The AUC for all other outcomes was poor.
Conclusions: The ACS NSQIP surgical risk calculator had a poor individual risk prediction (calibration) for all outcomes and only a fair discriminative ability (discrimination) to predict pneumonia and discharge not to home. The calculator might be considered to identify patients at high risk of pneumonia and discharge not to home to initiate additional preoperative interventions.
Keywords: Colorectal cancer; Elderly; External validation; Postoperative outcome; Surgery.
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