Abstract
Purpose: The aim of this study was to evaluate perineural invasion (PNI) of rectal cancer as a prognostic factor. Method: Subjects were 412 patients undergoing intestinal resection for rectal cancer, and patients who had undergone surgery between 1996 and 2005 were investigated retrospectively, of whom patients who received surgery between 2006 and 2010 were evaluated prospectively. Results: PNI was found in 144 patients (35.4%), of which 43.7% was in upper rectal cancerand 24.7% in lower. Multivariate logistic regression analysis showed that PNI was significantly associated with upper rectal cancer (P<0.001), lymphatic invasion (P<0.001), vascular invasion (P=0.003), and poorly differentiated component at tumor front (P=0.046). The PNI-positive group had a significantly worse survival curve. 3- and 5-year overall survival rates of PNI-positive cases were 56.2% and 37.3%, respectively. The survival rates of the PNI-negative group were 79.6% and 72.6% (P<0.001). The PNI-positive group in patients without lymphatic metastasis (stage II) also had poor prognosis, and the 5-year overall survival rate was 44.0%. In contrast, the survival rate for the PNI-negative group was 82.7% (P=0.008). The overall survival rate was significantly associated with lymph node metastasis (P<0.001), T3/T4 (P<0.001), and PNI (P=0.001), however, not associated with lymphatic invasion and vascular invasion. Local recurrence was also significantly related to T3/T4 (P<0.001, odd’s ratio 3.03), and PNI (P=0.003, odd’s ratio 2.60). Conclusion: In this study, PNI in patients with rectal cancer was significantly associated with prognosis and local recurrence. It was suggested that PNI was indispensable and valuable as a prognostic factor more than lymphatic invasion and vascular invasion.
