Surgery for pulmonary metastases from colorectal cancer: survival and prognostic factors

Background: This study aimed to describe overall survival following pulmonary metastasectomy for colorectal cancer (CRC) in Sweden, and to assess the discrimination of a recently proposed risk prediction model.

Methods: Individual-level data of 756 patients who underwent resection of pulmonary metastases from CRC between 2009 and 2015 were obtained from ThoR, a Swedish national quality register for thoracic surgery. We classified patients into three risk categories according to the number of preoperative risk factors [age, disease-free interval (DFI), presence of extrathoracic lesions, number of pulmonary metastases] established in a prior study. We estimated the hazard ratios (HRs) and 95% confidence interval (CI) by Cox regression and the restricted mean survival time difference as group contrast measures.

Results: During a median follow-up time of 2.9 years, 35% (268/756) patients died. At 5 years, overall survival was 56% (95% CI: 51-60%). In a Cox regression model with risk category as the only independent variable, the HR for all-cause mortality was 1.94 (95% CI: 1.38-2.72, P<0.001) and 4.35 (95% CI: 2.49-7.62, P<0.001) in the moderate- (n=558) and high-risk categories (n=32), respectively, versus the low-risk category (n=166). At 5 years, the differences in restricted mean survival time were 6 months (P<0.001) and 1.5 years (P<0.001) in the moderate- and high-risk categories, respectively, versus the low-risk category.

Conclusions: Five-year survival after surgery for pulmonary metastases from CRC in Sweden was similar or higher compared with contemporary reports. A prognostic model, initially developed in Japanese patients, had excellent discrimination in an external validation cohort of Swedish patients.