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

BACKGROUND: 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. OBJECTIVE: 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. DESIGN: This was a retrospective cohort study. SETTINGS: This study reviewed data from a tertiary care cancer center in Japan. PATIENTS: The records of 436 patients with pT3 or pT4a colon cancer who underwent curative resection between January 1996 and December 2006 were reviewed. MAIN OUTCOME MEASURES: 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. RESULTS: 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). LIMITATIONS: 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. CONCLUSIONS: 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.