Surgical Margin of Resected Colorectal Liver Metastases:: How Accurate is Surgeon Prediction?

Objective: The aim of this study was to describe the surgeon's ability to accurately predict the margin following resection of colorectal liver metastases (CRLM). Summary background data: The decision to resect CRLM is based on the surgeon's ability to predict tumor free resection margins. However, to date, no study has evaluated the accuracy of surgeon margin prediction. Methods: In this single-institution prospective study, the operating attending and fellow independently completed a preoperative and postoperative questionnaire describing their expected resection margin in 100 consecutive cases (200 assessments) of colorectal liver metastasis resections. In cases with multiple metastases, the closest margin was assessed as the margin of interest for the primary outcome. Surgeon assessments were compared to the gold-standard histopathologic assessment. Results: After excluding aborted cases, 190 preoperative and 190 postoperative assessments from 95 cases were included in the analysis. The pathologic margin was noted to be wide (≥1 cm), 1 mm to 1 cm, narrow (<1 mm), and positive in 28 (29.5%), 55 (57.9%), 5 (5.3%), and 7 (7.4%) cases, respectively. The 88 cases with negative margins were all predicted to be negative. None of the cases with positive margins were predicted to be positive. Ninety-one (48%) preoperative and 104 (55%) postoperative predictions were accurate. The sensitivity of predicting a margin <1 mm was 8.3% preoperatively and 16.7% postoperatively. The positive predictive value for preoperative and postoperative predictions of margin <1 mm was 18.2% and 26.7%, respectively. Conclusions: Surgeons are inaccurate at predicting positive and close surgical margins following resection of CRLM. A predicted close margin should not necessarily preclude resection.