Prognostic and Oncologic Significance of Perineural Invasion in Sporadic Colorectal Cancer.

BACKGROUND: The presence of perineural invasion (PNI) in colorectal cancer (CRC) indicates a more aggressive phenotype, resulting in a poor prognosis. The aims of this study were to evaluate the oncologic outcome of PNI+ tumors and to investigate whether PNI status affects patient survival.

METHODS: The study retrospectively enrolled 3807 patients from a single institution who underwent surgery for colorectal adenocarcinoma between January 2006 and December 2010. The patients were classified into two groups based on PNI status: PNI+ and PNI-.

RESULTS: The PNI+ group included 565 patients (14.8 %) and had significantly more involved circumferential resection margins (p = 0.001) and a more advanced TNM stage (p = 0.001) than the PNI- group. Compared with the PNI- group, the PNI+ group had worse 5-year overall survival (65 vs. 88 %; p = 0.001) and 5-year disease-free survival (63 vs. 85 %; p = 0.001). Among PNI+ patients with stage IIA disease, those who received adjuvant therapy had significantly greater 5-year overall survival than those who did not (89.3 vs. 50.8 %; p = 0.001). In multivariate analyses, PNI+ was an independent negative prognostic factor for 5-year overall survival (hazard ratio [HR] 1.518, 95 % confidence interval [CI] 1.175-1.961; p = 0.001) and 5-year disease-free survival (HR 1.495, 95 % CI 1.237-1.806; p = 0.001).

CONCLUSIONS: PNI positivity is an independent predictor of aggressive behavior and unfavorable prognosis in CRC. Further evaluation is needed to confirm the impact of PNI status on survival in stage IIA CRC.