Ki67 is an independent predictor of oncological outcomes in patients with localized clear-cell renal cell carcinoma

Objective To validate the impact of Ki67 expression on oncological outcomes of patients treated for clinically localized clear-cell renal cell carcinoma (ccRCC). Patients and Methods Immunohistochemistry for Ki67 was performed on tissue microarray constructs of patients treated with radical or partial nephrectomy for clinically localized (M0) ccRCC and Ki67 expression >10% was considered abnormal. Clinical and pathological data elements were entered into an institutional review board-approved database. The Kaplan-Meier method and Cox regression models were used to analyse disease-free survival (DFS) and cancer-specific survival (CSS) probabilities. Results Of 401 patients, 59.6% were males. The median (range) age was 58 (17-85) years, follow-up was 22 (0-150) months and time to death was 27 (0-150) months. A total of 20.2% of patients had advanced stage (pT3-T4) and 31% had advanced grade (3-4) disease. Abnormal expression of Ki67 was seen in 6.5% of our cohort and was associated with adverse pathological features (P < 0.05). Patients with high expression of Ki67 were found to have 5-year DFS and CSS rates of 67 and 84%, respectively, vs 87 and 95%, respectively, in those with normal expression (P < 0.001 and P < 0.05, respectively). In multivariable analyses, adjusting for stage and grade, abnormal Ki67 expression was an independent predictor of DFS (hazard ratio [HR] 3.77, P = 0.011, 95% confidence interval [CI] 1.35-10.52), but not of CSS (HR 3.51 P = 0.137, 95% CI 0.671-18.35). Conclusions Our findings support the role of Ki67 as a powerful independent predictor of inferior oncological outcomes in patients with ccRCC. Further prospective studies are needed to determine the clinical applicability of these findings.