Impact of the extent of lung resection on postoperative outcomes of pulmonary metastasectomy for colorectal cancer metastases: an exploratory systematic review

BACKGROUND: Pulmonary metastasectomy (PM) with curative intent has become a widely accepted treatment for lung metastases from solid tumours in selected patients, with low perioperative morbidity and mortality. In particular, PM is strongly recommended in selected patients with secondary lesions from colorectal cancer (CRC), due to its excellent postoperative prognosis. Nevertheless, the impact of the extent of PM on recurrence and survival remains controversial. This review aimed at assessing differences in short- and long-term postoperative outcomes depending on the extent of lung resection for lung metastases. METHODS: A systematic literature review of studies comparing anatomical and non-anatomical resections of lung metastases was performed (Prospective Register of Systematic Reviews Registration: 254931). A literature search for articles published in English between the date of database inception and January 31, 2021 was performed in EMBASE (via Ovid), MEDLINE (via PubMed) and Cochrane CENTRAL. Retrospective studies, randomised and non-randomised controlled trials were included. The Cochrane Collaboration tool was used to determine the risk of bias for the primary outcome for included studies. RESULTS: Out of 432 papers, three retrospective non-randomised studies (1,342 patients) were selected for systematic reviewing. Although our search design did not exclude any primary tumour histology, all selected studies investigated surgical resection of lung metastases from CRC. Because of variations in the compared surgical approaches to pulmonary metastases, a meta-analysis proved unfeasible. There was a tendency to perform anatomical resections for larger metastases. Multivariate analyses revealed that anatomical resections were protective for recurrence-free survival (RFS), while the impact of such procedures on overall survival (OS) remained uncertain. A significantly higher incidence of resection-margin recurrences was observed in patients who underwent non-anatomical resections. DISCUSSION: Anatomical resections of lung metastases from CRC seem to be associated with improved RFS. However, well-constructed comparative clinical trials focusing on the extent of PM are needed.