The Degree of Extramural Spread of T3 Colon Cancer as a Prognostic Factor: Another Appeal to the American Joint Committee on Cancer

Background

The pT3 category of colon cancer staging is heterogeneous and has significant prognostic value. However, this is not reflected in the current TNM staging system. The objective of this work is to determine whether the extent of infiltration beyond the muscularis propria of pT3 colon carcinoma is an independent risk factor for worse oncologic outcomes after curative surgery.

Methods

Retrospective analysis of 536 patients from a tertiary University Hospital with pT3M0 colon cancer (1995–2015) was collected and re-evaluated to assess tumor infiltration extent beyond the muscularis propria layer. The main outcome measures studied were local recurrence, systemic recurrence, disease-free survival, and cancer-specific survival.

Results

An infiltration extent of 5 mm was the best cutoff for predicting oncological results in this group of patients. Multivariable analysis showed that tumor infiltration depth into the pericolic fat was an independent risk factor for a higher local recurrence rate (p = 0.02, HR 1.11 per mm, 95% CI 1.04–1.23), a higher risk of systemic recurrence (p = 0.02, HR 1.08 per mm, 95% CI 1.01–1.16), worse disease-free survival (p = 0.008, HR 1.08 per mm, 95% CI 1.02–1.14), and cancer-specific survival (p = 0.009, HR 1.09 per mm, 95% CI 1.02–1.16). In a sub-analysis, these results were confirmed in patients with positive lymph nodes but not in the group of patients with negative lymph nodes.

Conclusions

The extramural spread of pT3 colon cancer is a significant prognostic factor for worse oncological outcomes after curative surgery. Therefore, this parameter should be considered in selecting adjuvant therapy and possibly included in the TNM staging system.