Purpose: By defining perineural invasion of colorectal cancer as invasion to Auerbach's plexus, we examined the usefulness of this pathologic finding as a prognostic factor.
Methods: A total of 509 consecutive patients who underwent curative surgery for pT3 or pT4 colorectal cancer between May 1997 and December 2001 were reviewed. All the surviving patients were followed for more than five years. All the pathologic findings, including perineural invasion, were described prospectively in the pathology report forms.
Results: Perineural invasion was detected in 132 of 509 patients (26 percent) and was significantly associated with lymph node status, lymphatic invasion, and venous invasion. Incidences of local and systemic recurrence were significantly higher in patients with perineural invasion than in those without perineural invasion. The disease-free survival of the perineural invasion-positive group was significantly poorer than that of the perineural invasion-negative group for Stages II and III colon cancer, irrespective of the use of adjuvant chemotherapy. This improved disease-free survival also was seen in patients with Stage II rectal cancer not treated with adjuvant chemotherapy. There was a nonsignificant difference in disease-free survival for Stage II rectal cancer and Stage III rectal cancer treated with chemotherapy, that of the perineural invasion-positive group being poorer. Multivariate analysis showed that lymph node status, perineural invasion, depth of invasion, and cancer site were significant prognostic factors.
Conclusions: Perineural invasion defined as cancer invasion to Auerbach's plexus is an important prognostic factor for colorectal cancer.