Association between Ki67 Index and Clinicopathological Features in Colorectal Cancer

BACKGROUND: Conflicting results have been reported about the association between the Ki67 labeling index (Ki67-Li) and clinical outcome in patients with colorectal cancer (CRC). PATIENTS AND METHODS: Ki67 expression was assessed by immunohistochemistry (IHC) in 2,233 consecutive CRC cases. RESULTS: We determined 992 cases to have a low and 1,241 cases to have a high Ki67-Li (representing an approximately 44-56% breakdown in distribution between low versus high patients designated by phenotype). Stage III patients with a high Ki67-Li had higher 3-year disease-free survival (DFS) and overall survival (OS) than those with a low Ki67-Li (DFS 70 vs. 61%; p = 0.02 and OS 75 vs. 64%; p = 0.008). We also found significantly improved 3-year progression-free survival (PFS) for stage IV patients in the high versus the low Ki67-Li group (PFS 14 vs. 10%; p = 0.02). Yet, we found no statistical differences in prognosis for stage I and II patients and in OS for stage IV patients between high versus low Ki67-Li (p > 0.05). CONCLUSION: Our results suggest that high Ki67-Li can be an independent prognostic biomarker to aid the assessment of patient outcomes in both stage III and IV CRC.