Long‐term outcomes and prognostic factor of metachronous para‐aortic lymph node metastasis in colorectal cancer

Abstract Aim Despite the relatively rare incidence of para‐aortic lymph node metastasis (PALNM) after surgery for colorectal cancer, it is often fatal, and treatment strategy is still debated. This study aimed to investigate the long‐term outcomes of patients with metachronous PALNM and their prognostic factors. Method Thirty‐six institutions belonging to the Japanese Society for Cancer of the Colon and Rectum participated in this retrospective cohort study. A total of 148 patients with metachronous PALNM after resection of primary colorectal cancer between January 2011 and December 2015 were included in the analysis. Results Of the 148 patients, 37 received PALNM resection, whereas 111 did not. The primary tumour characteristics were not different between the resection and non‐resection groups. The median number of PALNMs was significantly larger and synchronous metastasis other than PALNM was more frequent in the non‐resection group than in the resection group (2 vs. 1, P = 0.030; 71.2% vs. 29.7%, P < 0.001). The 5‐year overall survival rate in the whole cohort was 30.6%, which was significantly higher in the resection group than in the non‐resection group ( P < 0.0001). The resection method of PALNM did not affect survival. Undifferentiated tumour, ≥4 PALNMs, synchronous metastasis other than PALNM, and non‐resection of PALNM were significant unfavourable prognostic factors in the multivariate Cox regression analysis. Conclusion PALNM resection appears desirable when it is feasible in patients with metachronous PALNM. However, surgeons should also consider unfavourable prognostic factors including undifferentiated tumour, ≥4 PALNMs and synchronous metastasis other than PALNM.