The proportion of tumor-stroma as a strong prognosticator for stage II and III colon cancer patients: validation in the VICTOR trial

Background: The intra-tumor stroma percentage in colon cancer (CC) patients has previously been reported by our group as a strong independent prognostic parameter. Patients with a high stroma percentage within the primary tumor have a poor prognosis. Patients and methods: Tissue samples from the most invasive part of the primary tumor of 710 patients (52% Stage II, 48% Stage III) participating in the VICTOR trial were analyzed for their tumor-stroma percentage. Stroma-high (>50%) and stroma-low (≤50%) groups were evaluated with respect to survival times. Results: Overall and disease-free survival times (OS and DFS) were significantly lower in the stroma-high group (OS P < 0.0001, hazard ratio (HR) = 1.96; DFS P < 0.0001, HR = 2.15). The 5-year OS was 69.0% versus 83.4% and DFS 58.6% versus 77.3% for stroma-high versus stroma-low patients. Conclusion: This study confirms the intra-tumor stroma ratio as a prognostic factor. This parameter could be a valuable and low cost addition to the TNM status and next to current high-risk parameters such as microsatellite instability status used in routine pathology reporting. When adding the stroma-parameter to the ASCO criteria, the rate of ‘undertreated’ patients dropped from 5.9% to 4.3%, the ‘overtreated’ increased with 6.8% but the correctly classified increased with an additional 14%.