BackgroundPulmonary metastasectomy is considered a potentially curative treatment for selected patients with metastatic colorectal cancer (CRC). Several prognostic factors have been analysed, but to date, it is still not well defined which is the optimal resection margin during lung metastasectomy (LM). This study analyses the long-term results and prognostic factors after LM in CRC patients with particular attention to the resection margins. Primary endpoint of this study is to assess the correlation between resection margins and long-term outcomes.MethodsObservational cohort study on all proven cases of CRC lung metastases (2000–2016) resected with curative intent in a single centre.ResultsThe series included 210 consecutive patients (M/F 133/77) with a mean age of 65.4 (± 9.96) years, 75% (159/210) of them with a solitary metastasis. Mean size of metastasis was 2.57 cm (± 1.45). One hundred sixty-eight patients underwent wedge resections (80%) and lymphadenectomy was carried out in 90 cases (42.9%). With a mean follow-up of 56 months (range 5–192), we observed a 1-, 3- and 5-year overall survival (OS) of 95%, 74% and 54%, respectively. The patients were divided into three groups according to the resection margin distance from the tumour: (a) ≥ 2 cm (145 cases); (b) < 2, ≥ 1 cm (37 cases); and (c) < 1 cm (12 cases). The OS was significantly different between the three groups (p = 0,020); univariate and multivariate analyses showed that a narrow resection margin was an independent prognostic factor of worse survival (p = 0.006 and HR 3.4 p = 0.009).ConclusionsLong-term survival of patients after LM is strongly associated with a greater distance between the lesion and the resection margin.