Clinical impact of elastic laminal invasion in colon cancer: elastic laminal invasion-positive stage II colon cancer is a high-risk equivalent to stage III.

Abstract

Elastic laminal invasion is defined as tumor invasion beyond the peritoneal elastic lamina. It is one of the factors affecting the prognosis of patients with colon cancer. This study aimed to investigate the clinical impact of elastic laminal invasion in colon cancer and the magnitude of the worse prognosis of elastic laminal invasion-positive, node-negative patients. This was a retrospective cohort study. This study reviewed data from a tertiary care cancer center in Japan. The records of 436 patients with pT3 or pT4a colon cancer who underwent curative resection between January 1996 and December 2006 were reviewed. The primary outcome measure was recurrence-free survival. Cox regression analyses established the factors associated with recurrence-free survival. Six groups formed by combining the factors were compared. Of the patients with pT3 disease, those who were positive for elastic laminal invasion had a 5-year recurrence-free survival rate of 73.8% compared with a rate of 85.0% in those who were negative for elastic laminal invasion and 53.5% in patients with pT4 disease. Three unfavorable prognostic factors were identified, including lymph node metastasis, positive elastic laminal invasion, and a lack of adjuvant chemotherapy. Log-rank analysis revealed statistically significant differences in recurrence-free survival between group 1 (node negative, elastic laminal invasion negative, and no adjuvant chemotherapy) and group 3 (node negative, elastic laminal invasion positive, and no adjuvant chemotherapy). The HR for group 1 compared with group 3 was 0.49 (95% CI, 0.27-0.90). Furthermore, the HRs for group 2 (node positive, elastic laminal invasion negative, and received adjuvant chemotherapy) and group 4 (node positive, elastic laminal invasion positive, and received adjuvant chemotherapy) vs group 3 were 0.77 (95% CI, 0.35-1.69) and 1.36 (95% CI, 0.62-2.98). Our study has limited prediction accuracy of our prognostic stratification, and an analysis of small subgroups may not have been capable of detecting significant differences. In addition, a wide range of hematoxylin and eosin- and elastica-stained slides were examined per case. Elastic laminal invasion adversely influences prognosis in pT3 and pT4a colon cancer. Although elastic laminal invasion positivity does not affect prognosis in node-positive patients receiving adjuvant chemotherapy, node-negative patients with elastic laminal invasion have a similar risk of recurrence as node-positive patients.