Optimal timing for lung metastasectomy in patients with colorectal cancer

OBJECTIVES: The possibility of occult metastasis remains a concern when deciding on lung metastasectomy. This study aimed to evaluate the utility of our two-step determination, which required confirmation that no new metastases had occurred over 3 months before surgery. METHODS: Patients who were referred for colorectal lung metastases between 2007 and 2015 were reviewed. Immediate wedge resection was performed for cases with a single peripheral metastasis, whereas surgical indications for others were determined by the two-step determination. Early increase was defined as the emergence of new metastases within 4 months after the diagnosis of lung metastases. RESULTS: Among 369 patients included, 92 were unresectable upon initial diagnosis, and 74 with single peripheral metastasis underwent immediate wedge resection. Surgical indications for the remaining 203 patients were ascertained based on the two-step determination. Surgery was not indicated in 48 patients (24%) due to new metastases or a favourable response to chemotherapy, with a median waiting duration of 4.8 months. Those who did not receive surgery had a worse prognosis than those who did (5-year overall survival: 21% vs 69%, P < 0.001) and were comparable to the initially unresectable group (5-year overall survival: 23%). Thirty-eight patients with early increase had lower surgical resection rates and worse prognoses than those without. Multivariable analysis identified early increase as an independent prognostic factor (hazard ratio: 4.49, P < 0.001). CONCLUSIONS: Patients with colorectal lung metastasis who developed new metastasis during the waiting period exhibited poor prognosis, suggesting the utility of the two-step determination of surgical indications.