title: Perineural invasion is an independent predictor of outcome in colorectal cancer.
abstract: OBJECTIVE
  Perineural invasion (PNI) is associated with decreased survival in several malignancies, but its significance in colorectal cancer (CRC) remains to be clearly defined. We evaluated PNI as a potential prognostic indicator in CRC, focusing on its significance in node-negative patients.
  
  
  METHODS
  We identified 269 consecutive patients who had CRC resected at our institution. Tumors were re-reviewed for PNI by a pathologist blinded to the patients' outcomes. Overall and disease-free survivals were determined using the Kaplan-Meier method, with differences determined by multivariate analysis using the Cox multiple hazards model. Results were compared using the log-rank test.
  
  
  RESULTS
  PNI was identified in less than 0.5% of the initial pathology reports. On rereview, 22% of tumors in our series were found to be PNI positive. The 5-year disease-free survival rate was four-fold greater for patients with PNI-negative tumors versus those with PNI-positive tumors (65% v 16%, respectively; P < .0001). The 5-year overall survival rate was 72% for PNI-negative tumors versus 25% for PNI-positive tumors. On multivariate analysis, PNI was an independent prognostic factor for both cancer-specific overall and disease-free survival. In a subset analysis comparing patients with node-negative disease with patients with stage III disease, the 5-year disease-free survival rate was 56% for stage III patients versus 29% for patients with node-negative, PNI-positive tumors (P = .0002). Similar results were seen for overall survival.
  
  
  CONCLUSIONS
  PNI is grossly underreported in CRC and could serve as an independent prognostic factor of outcomes in these patients. PNI should be considered when stratifying CRC patients for adjuvant treatment.
authors.affiliation: Department of Surgery, Michael E. DeBakey Veterans Affairs Medical Center, Houston, TX 77030, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Liebig
authors.forename: Gustavo
authors.initials: G
authors.lastname: Ayala
authors.forename: Jonathan
authors.initials: J
authors.lastname: Wilks
authors.forename: Gordana
authors.initials: G
authors.lastname: Verstovsek
authors.forename: Hao
authors.initials: H
authors.lastname: Liu
authors.forename: Neeti
authors.initials: N
authors.lastname: Agarwal
authors.forename: David H
authors.initials: DH
authors.lastname: Berger
authors.forename: Daniel
authors.initials: D
authors.lastname: Albo
mesh_terms: D000230:Adenocarcinoma / Q000401:mortality* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use; D017024:Chemotherapy, Adjuvant; D015179:Colorectal Neoplasms / Q000401:mortality* / Q000473:pathology* / Q000628:therapy; D003131:Combined Modality Therapy; D013505:Digestive System Surgical Procedures; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D009361:Neoplasm Invasiveness / Q000473:pathology; D009367:Neoplasm Staging; D010525:Peripheral Nerves / Q000473:pathology*; D011379:Prognosis; D011878:Radiotherapy; D018714:Radiotherapy, Adjuvant; D016896:Treatment Outcome
chemical_list: D000970:Antineoplastic Agents