Background: 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.
Patient and methods: 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.
Results: 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).
Conclusions: 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.
Keywords: Adjuvant chemotherapy; Colorectal cancer; Propensity score matching; Pulmonary metastasis.
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