OBJECTIVETo investigate the association of peripheral nerve invasion (PNI) with clinicopathological factors and prognosis of colorectal cancer.

METHODSClinicopathological data and Surgical specimens of 372 colorectal cancer patients who underwent radical resection from January 2011 to June 2012 in The Second Affiliated Hospital of Harbin Medical University were collected. Histopathological evaluation of tissue samples was conducted with hematoxylin and eosin-stained sections. PNI was considered positive when cancer cells were observed inside the nerve sheath, or when at least 33% of the nerve periphery was surrounded by cancer cells. The relationship between PNI and clinicopathological factors of colorectal cancer was analyzed by χtest or Fisher's exact test. Three-year overall survivals of PNI positive and negative patients were determined using the Kaplan-Meier method. Detection results were compared using log-rank test.

RESULTSOf 372 colorectal cancer patients, 133 (35.8%) were PNI positive. Among the PNI positive patients, 63 cases were male and 70 cases female; 76 cases were more than 60 years old and 57 cases less than 60 years old; tumors of 6 cases located in the ileocecal colon, of 33 cases in the ascending colon, of 7 cases in the transverse colon, of 8 cases in the descending colon, of 22 cases in the sigmoid colon, and of 57 cases in the rectum; tumor diameter was greater than 4 cm in 83 cases, and less than 4 cm in 50 cases; tumors of 48 cases were moderately or highly differentiated, and of 85 cases poorly-differentiation; tumor invasion depth in 2 cases, T2 in 7 cases, T3 in 93 cases, T4 in 31 cases; lymphatic metastasis was N0 phase in 56 cases, N1 in 41 cases, and N2 in 36 cases; tumors were stage I( in 2 cases, stage II( in 40 cases, of stage III( in 75 cases and stage IIII( in 16 cases. The positive rate of PNI was significantly associated with tumor location (χ=11.20, P=0.048), tumor size (χ=21.80, P=0.000), differentiation (χ=60.90, P=0.000), depth of invasion (χ=19.00, P=0.000), lymph node metastasis (χ=19.70, P=0.000) and TNM staging (χ=70.80, P=0.000), but not with sex, age or vascular invasion(P>0.05). The median follow-up time was 48 (8 to 62) months. Kaplan-Meier survival curve showed that the 3-year survival rate of PNI positive patients was 52.6%, significantly lower than that of PNI negative patients(78.3%, P=0.000). Further analysis of patients with stage II( and III( colorectal cancer showed that the 3-year survival rates of PNI positive patients were 62.3% and 43.5%, respectively, which were significantly lower than those of PNI negative patients with stage II( and III((91.7% and 79.4%), and the differences were statistically significant(P=0.000).

CONCLUSIONSPNI is a poor prognostic factor of colorectal cancer. It may be a complement of the classic TNM staging classification in stratifying colorectal cancer patients, especially in stages II( and III(.