Prognostic value of the number and size of venous invasions in pT3 colorectal cancer: a prospective observational study.

Abstract

Although venous invasion is reportedly a clinically useful prognostic marker for colorectal cancer, suitable grading criteria have not been established. This prospective observational study aimed to investigate the prognostic value of the number and size of venous invasions in patients with pT3 colorectal cancer. We recruited 139 consecutive patients with pT3 colorectal carcinomas resected between October 2001 and August 2003. We used slides of whole-tissue sections stained with Elastica van Gieson. Venous invasion was classified according to the number of veins with carcinoma infiltration per slide with most venous invasions (V-number classification): V(n)-low 0-3 and V(n)-high ≥4. Additionally, the findings were classified according to the maximal size of veins containing carcinoma infiltration (V-size classification): V(s)-low <1 mm and V(s)-high ≥1 mm. The grades of venous invasions were evaluated just after surgery. The 5-year survival rate of V(n)-low and V(n)-high were 89.9 and 59.1 %, respectively (p < 0.0001). Comparisons between overall survival curves revealed that V-number classification (but not V-size classification) had a significant prognostic value in patients with pT3 cancer, especially in stage II patients (98.2 and 64.2 %, respectively; p < 0.0001). Multivariate analysis revealed distant metastasis, age, and V-number classification (hazard ratio 3.1; p = 0.0071) as independent prognostic indicators. V-number classification may be a useful prognostic system when evaluating and sub-grouping patients with pT3 colorectal cancer.