Clinical significance of systemic chemotherapy after curative resection of metachronous pulmonary metastases from colorectal cancer

The use of systemic chemotherapy after resection remains controversial in patients with resectable metachronous pulmonary metastases from colorectal cancer (CRC). This retrospective study compared systemic chemotherapy with observation alone after resection of pulmonary metastases from CRC. Between 2001 and 2015, 91 patients with metachronous pulmonary metastases underwent curative surgical resection at five centers. Patients with stage IV at diagnosis were excluded. Overall survival (OS) was defined as the time from pulmonary resection until death. The disease-free interval (DFI) was defined as the time from pulmonary resection until recurrence or death. Among the 91 patients, 63 were in the chemotherapy group, while 28 were in the observation alone group. The characteristics were similar between the two groups, except for the carcinoembryonic antigen level after pulmonary metastases and the use of adjuvant treatment after resection of the primary tumor. With a median follow-up duration of 46 months (11-126), the estimated 5-year DFI and OS rates were 32.8 and 61.4%, respectively. The chemotherapy following pulmonary resection was not significantly associated with the DFI (p = 0.416) and OS (p = 0.119). Systemic chemotherapy after pulmonary resection was not found to have a significant effect on survival.