Horizontal Tumor Size is Inversely Related to Prognosis in Nodal-Positive Stage III Colorectal Cancer

Abstract

Purpose. Vertical tumor growth, reflected by the T classification, is the most important prognostic variable in colorectal cancer. However, the data regarding the prognostic impact of horizontal tumor size are limited and contradictory. In the present study, we aimed to investigate the effect of maximal horizontal tumor size on patient outcome in patients with nodal-positive stage III colorectal cancer. Methods. We retrospectively reviewed the medical records from 1996 to 2009. We included individuals diagnosed with nodal-positive stage III colorectal cancer who underwent surgical resection, and for whom complete medical records were available. In our analysis, the cut-off values for tumor size were set at 1.0 cm and 0.5 cm. A Kaplan-Meier survival analysis and the Cox proportional hazard model were applied to the data for further analysis. Results. In total, 939 nodal-positive stage III colorectal cancer specimens were reviewed retrospectively. We classified the patients into two groups: those with a maximum horizontal tumor size of ＜ 1.0 cm (57 patients; 6%) and those with a maximum horizontal tumor size of ＞ 1.0 cm (887 patients; 94%).With regard to the TNM classification, the group of patients with tumors ＜ 1.0 cm in size had a greater number of T1-2 stage tumors compared to the group with tumors ＞ 1.0 cm in size (42.1% vs. 27%, p = 0.02).With regard to the primary tumor site, the group of patients with tumors ＜ 1.0 cm in size had a greater number of rectal tumors compared to the group with tumors ＞ 1.0 cm in size (61.7% vs. 45%, p = 0.01). The median disease-free-survival was shorter in patients with tumors ＜ 1.0 cm in size than in patients with tumors ＞ 1.0 cm in size (6.96 months vs. 17.64 months, p = 0.003). Survival was significantly different between these two groups of patients as well (p = 0.008). Using a Cox proportional hazard model, the hazard ratio was found to be 2.29 for patients with tumors ＜ 0.5 cm in size and 1.224 for those whose tumor measured 0.5-1.0 cm in size. Further multivariate analysis also demonstrated that small tumor size is a significant risk factor for a negative prognosis (p = 0.01). Conclusion. In nodal-positive stage III colorectal cancer, tumor size is inversely related to prognosis. We postulated that smaller nodal-positive tumors would display significantly more aggressive tumor behavior as compared to larger tumors. However, these interesting findings require further investigation to corroborate the results.