Perineural and lymphovascular invasion predicts for poor prognosis in locally advanced rectal cancer after neoadjuvant chemoradiotherapy and surgery

Background: Perineural invasion (PNI) and lymphovascular invasion (LVI) are associated with poor prognosis in colorectal cancer, but their clinical significance is still controversial for patients with locally advanced rectal cancer (LARC) who had received neoadjuvant chemoradiotherapy (nCRT) and surgical resection. The aim of this study was to confirm the correlation between PNI and/or LVI and clinical prognosis and to further confirm whether PNI and/or LVI can be used as potential prognostic indicators of adjuvant chemotherapy after nCRT and surgery in LARC. Methods: From February 2002 to December 2012, a total of 181 patients with LARC who had received nCRT and surgical resection were retrospectively reviewed. Overall survival (OS) and disease-free survival (DFS) were determined by the Kaplan-Meier method, log-rank test, and Cox proportional hazard regression model. Results: The median follow-up time was 48 months (range, 3 to 162 months). All the PNI-positive and/or LVI-positive patients showed adverse DFS and OS (P<0.001). In multivariate analysis, PNI and LVI were independent prognostic factors for DFS. PNI, rather than LVI, was also an independent prognostic factor for OS. In a subgroup analysis, PNI-positive, rather than LVI-positive, may benefit from adjuvant chemotherapy. Conclusion: For patients with LARC undergoing nCRT and surgery, PNI-positive and/or LVI positive were associated with poorer DFS and OS. And PNI-positive, rather than LVI-positive, may benefit from adjuvant chemotherapy.