PD-0007A COMMON GENE VARIANT IN HEDGEHOG PATHWAY GENE GLI1 IDENTIFIES PATIENTS AT RISK OF RECURRENCE IN STAGE II COLON CANCER

2) tests. ACox regression model was used to evaluate the Relapse Free Survival (RFS) and the Colon Cancer specific Survival. Results: MSI status could be determined by genotyping in 350 tumor samples. 48 patients (14%) had MSI high (MSI-H) tumors and 302 (86%) had microsatellite stable (MSS) tumor. BRAF status could be determined in 380 tumor samples. 58 cases (15%) were BRAF mutated tumors and 322 (85%) were BRAF wild type tumors. Tumor-stroma ratio was analyzed in 407 cases. 176 tumors (43%) had more than 50% intra-tumor stroma and were classified as stroma-high. MSI-H tumors were significantly located in the right colon (X 2 p-value = 1.03e-5), were poorly differentiated (X 2 p-value = 0.003) and had more than 12 lymph nodes resected (X 2 p-value = 0.037). MSI-H tumors were associated with BRAF mutation (X 2 p-value = 0.02) and stroma-low (X 2 p-value = 0.0005). When a molecular prognostic risk classification was performed, patients with MSI-H and stroma-low suggested a low risk of relapse comparing to MSI-H/stroma-high, MSS/stroma-low and MSS/ stroma-high (Hazard Ratio = 3.15; 95% CI, 0.76 - 13.1, p-value = 0.0602). Conclusion: MSI-H tumors are typically poorly differentiated, located in the right colon and have BRAF mutation as well as low intra-tumor stroma. Our results suggest that low-stroma could partly explain prognosis in patients with MSI-H stage II tumors.