Impact of regional lymph node metastasis on pulmonary metastasis as the first recurrence site

Little is known about the impact of regional lymph node metastasis (LNM) on the first recurrence sites following curative colorectal cancer (CRC) surgery. The present study aimed to clarify the relationship between regional LNM stratified by N status and the first recurrence pattern in patients with stage I-III CRC. We performed a retrospective analysis of 1181 consecutive patients with stage I-III CRC who underwent curative surgery between 2010 and 2018. The total sample size included 1181 patients who underwent elective stage I-III CRC surgery. Median follow-up time was 60 months, and median time to recurrence was 12 months. Overall, the numbers of liver recurrence and pulmonary recurrence were 94 (7.9%) and 70 (5.9%), respectively. Higher N status was significantly associated with increased risk of pulmonary recurrence (N0 vs. N1a, p = 0.02; N0 vs. N1b, p < 0.01; N0 vs. N2a, p < 0.01; N0 vs. N2b, p < 0.01) and worse pulmonary recurrence-free survival, but not other recurrences. In Non-LNM patients, on the other hand, advanced T status was associated with increased risk of pulmonary recurrence. The regional LNM was strongly associated with pulmonary metastasis as the first recurrence site following stage I-III CRC resection.