Thoracoscopic surgery versus open surgery for lung metastases of colorectal cancer: a multi-institutional retrospective analysis using propensity score adjustment†.

OBJECTIVES: Thoracoscopic surgery for lung metastasectomy remains controversial. The study aimed at determining the efficacy of thoracoscopic surgery for lung metastasectomy. METHODS: This was a multi-institutional, retrospective study that included 1047 patients who underwent lung metastasectomy for colorectal cancer between 1999 and 2014. Prognostic factors of overall survival were compared between the thoracoscopic and open thoracotomy groups using the multivariate Cox proportional hazard model. The propensity score, calculated using the preoperative covariates, included the era of lung surgery as a covariate. A stepwise backward elimination method, with a probability level of 0.15, was used to select the most powerful sets of outcome predictors. The difference between the radiological tumour number and the resected tumour number (delta_num) was also evaluated. RESULTS: The c-statistics and the P-value of the Hosmer-Lemeshow Chi-square of the propensity score model were 0.7149 and 0.1579, respectively. After adjusting for the propensity score, the thoracoscopy group had a better survival rate than the open group (stratified log-rank test: P = 0.0353). After adjusting for the propensity score, the most powerful predictive model for overall survival was that which combined thoracoscopy [hazard ratio (HR): 0.468, 95% CI: 0.262-0.838, P = 0.011] and anatomical resection (HR: 1.49, 95% CI: 1.134-1.953, P = 0.004). Before adjusting for the propensity score, the delta_num was significantly greater in the open group than in the thoracoscopy group (thoracoscopy: 0.06, open: 0.33, P = 0.001); however, after adjustment, there was no difference in the delta_num (thoracoscopy: 0.04, open: 0.19, P = 0.114). CONCLUSIONS: Thoracoscopic metastasectomy showed better overall survival than the open approach in this analysis. The thoracoscopic approach may be an acceptable option for resection of pulmonary metastases in terms of tumour identification and survival outcome in the current era.