Surgical margins and risk of local recurrence after wedge resection of colorectal pulmonary metastases

Objective: During resection of pulmonary metastases, the need to spare lung parenchyma is often weighed against the increased risk of local recurrence if an inadequate surgical margin is obtained. We sought to identify risk factors for local recurrence after wedge resection of pulmonary metastases of a colorectal origin. Methods: A retrospective study of patients who underwent a wedge resection for colorectal pulmonary metastases from 2006 to 2016 was performed. Cox regression with robust variance was used to estimate the risk of local recurrence per nodule treated. Results: We identified 335 patients who underwent 679 wedge resections. The 2-year local recurrence risk for each nodule was 11.8%(95% confidence interval, 8.9%-14.6%), and the 5-year risk was 20.6%(95% confidence interval, 16.2%-24.8%). Longer margin length decreased the risk of local recurrence (hazard ratio, 0.434 per additional cm of length; P = .015), whereas larger tumor size increased this risk (hazard ratio, 1.520 per additional cm of size; P = .012). However, other factors tested, including tumor grade, KRAS mutation status, and response to induction chemotherapy, did not affect recurrence risk. A pathologic margin length of at least half the tumor size was estimated to result in a local recurrence rate <11%. Conclusions: Among surgically resected colorectal pulmonary metastases, technical factors related to margin length and tumor size were associated with the risk of local recurrence, whereas tumor grade and KRAS status were not. However, the increased risk of local recurrence with larger tumors was diminished with a sufficient margin length.