The prognostic importance of the number of metastases in pulmonary metastasectomy of colorectal cancer

BACKGROUND The presence of multiple metastatic pulmonary nodules is a predictor of poor survival after pulmonary metastasectomy. However, there is a paucity of data addressing the exact number of pulmonary metastases over which prognosis becomes grave. The aim of our study is to investigate the prognosis of pulmonary metastasectomy from colorectal cancer (CRC) depending on the number of pulmonary metastases. METHODS Patients who had undergone pulmonary metastasectomy for CRC between November 1994 and December 2013 were included. Survival and recurrence patterns were analyzed with regard to the number of pulmonary metastases. Patients were divided into three groups depending on the number of pulmonary metastases that were detected by the final pathologic report: group I--single metastasis; group II--2-3 metastases; and group III--4+ metastases. RESULTS A total of 615 patients who had undergone pulmonary metastasectomy from colorectal cancer were included. The median follow-up period was 31 months (range 2-211 months). The median disease-free interval (DFI) from the time of the primary operation for colorectal cancer was 20 months (range 0-209 months). There were 414 patients in group I (single metastasis), 159 in group II (2-3 metastases), and 42 in group III (4+ metastases). The overall 5-year survival rate was 64.2%. The 5-year survival rates in groups I, II, and III were 70.0, 56.2, and 33.7%, respectively (group I vs. II, p<0.001; group II vs. III, p=0.012). The 5-year recurrence-free rates were 39.5, 30.6, and 8.5% in groups I, II, and III, respectively (group I vs. II, p<0.001; group II vs. III, p=0.056). Multivariable analysis revealed that age, multiple pulmonary nodules, thoracic lymph node metastasis, and adjuvant chemotherapy are independent predictors of survival. CONCLUSIONS The overall survival and recurrence after pulmonary metastasectomy for CRC is dependent on the number of metastases. Surgical treatment can be offered to patients with three or fewer pulmonary metastases. However, more meticulous patient selection is required to decide whether a surgical approach is feasible in patients with four or more pulmonary metastases.