Disease-Free Survival of Patients with Stage II Stroma-Rich Colorectal Adenocarcinomas with Microsatellite Stability

Up to 25% of stage II colorectal adenocarcinomas recur within the first five years after diagnosis. The assessment of the stromal percentage, recently incorporated into the TNM classification system, may represent a particularly relevant predictive factor for recurrence in cases with microsatellite stability. We evaluated disease-free survival (DFS) in an independent retrospective cohort, measured the stromal percentage across the entire invasive front of the tumor, and assessed the interobserver agreement of this measurement method. Among 131 cases, 16 (12.2%) showed a high stromal percentage and 115 (87.8%) a low one. A high stromal percentage was associated with high-grade budding (p = 0.006). The 5-year DFS was 57% for high-stroma cases versus 76% for low-stroma cases (p < 0.001). Lymphatic invasion (HR: 16.513; p < 0.001) and a high stromal percentage (HR: 4.366; p = 0.006) had a statistically significant correlation with DFS. Interobserver agreement for global stromal assessment was very good (kappa index = 0.870; p < 0.001). In conclusion, the stromal percentage may be a predictive factor for recurrence, particularly relevant in stage II microsatellite-stable colorectal adenocarcinomas. Global stromal assessment appears to be a simple and easily reproducible method.