Efficacy of adjuvant chemotherapy after resection of pulmonary metastasis from colorectal cancer: a propensity score–matched analysis

Pulmonary metastases from colorectal cancer are resected due to the favourable 5-year overall survival rates of 30–60% reported in many studies. However, the efficacy of subsequent adjuvant chemotherapy remains unclear. We retrospectively collected clinical data of 1237 patients who underwent surgical resection of pulmonary metastasis from colorectal cancer at 46 Japanese institutions between 2004 and 2008. Patients with non-curative resection, pre-operative chemotherapy, extra-thoracic metastasis, complications after surgery, and inadequate data were excluded. Then, a 1:1 propensity score nearest-neighbour matching between patients with and without adjuvant chemotherapy was performed, considering relevant co-variables, and survival of patients between groups was compared. Data of 524 patients (surgery alone, 269 patients; surgery with adjuvant chemotherapy, 255 patients) were used for matching. From each group, 192 patients with similar background characteristics between groups were selected. Adjuvant chemotherapies included fluoropyrimidine alone (71%), an oxaliplatin-containing regimen (23%), or an irinotecan-containing regimen (6%). In the surgery alone and adjuvant chemotherapy groups, 5-year overall survival rates were 68% and 69%, and 5-year disease-free survival rates were 40% and 34%, respectively. There were no significant differences between the two groups in terms of overall survival (hazard ratio [HR]: 1.00, 95% confidence interval [CI]: 0.69–1.45, P = 1.00) and disease-free survival (HR: 1.07, 95% CI: 0.82–1.39, P = 0.62). Adjuvant chemotherapy after curative resection of lung-limited metastasis from colorectal cancer did not show a survival benefit in the propensity score–matched analysis and should not be recommended without further clinical trials. •Pulmonary metastases (PM) from colorectal cancer (CRC) are resected.•Five-year survival rates after resection of PM from CRC are 30–60%.•Efficacy of adjuvant chemotherapy after resection of PM is unclear.•We used the propensity score nearest-neighbour matching method to minimise bias.•Adjuvant chemotherapy showed no survival benefit after resection of PM.