Tumor budding and poorly-differentiated cluster in prognostication in Stage II colon cancer

Comparison between tumor budding (TB) and poorly-differentiated clusters (PDC) for prognostication in Stage II colon cancer was not extensively studied in literature. In this retrospective study, we assessed TB (according to the consensus statement in 2016) and PDC in 135 Stage II colon adenocarcinoma resection specimens. Counting of TB and PDC was performed on H&E slides. High-grade TB (Bd3 (≥10 tumor buds in 0.785 mm²)) and high-grade PDC (Grade 3 (≥10)) were found in 20% and 17% of cases respectively. High-grade TB was associated with pT4 (p = 0.008) and presence of lymphovascular invasion (p = 0.001). There was correlation between TB and PDC grades (p < 0.001), in which both grades were the same or one grade apart in majority of the cases (95%). Both TB and PDC correlated with 5-year disease-specific survival (DSS) and overall survival (OS) (DSS for TB: 89% (Bd1); 73% (Bd2); 52% (Bd3), p = 0.001) (DSS for PDC: 88% (Grade 1); 72% (Grade 2); 61% (Grade 3), p = 0.021). Survival curves of Stage II colon cancer could be further stratified by TB and PDC (log-rank tests: TB p < 0.001; PDC p = 0.009). Combining TB and PDC grades into single grading system (high-grade: Bd3 + G2, Bd2 + G3, Bd3 + G3; low-grade: other combinations) was found to have strong correlation with both 5-year DSS and OS (both p < 0.001). Our study has confirmed TB and PDC as independent prognostic factors in Stage II colon cancer, and might help selecting high-risk patients for adjuvant chemotherapy.