Prognostic Value of Ki67 in Patients with Stage 1–2 Endometrial Cancer: Validation of the Cut-off Value of Ki67 as a Predictive Factor

OBJECTIVE: The purpose of this study was to find a cut-off value of the immunohistochemical parameter Ki67 for stage I–II endometrial cancer. MATERIALS AND METHODS: The clinicopathological data of 318 patients with stages I–II endometrial cancer who received primary surgical treatment were retrospectively analyzed. A cut-off value of Ki67 for predicting recurrence of endometrial cancer was determined by using the receiver operating characteristic curve and the Youden index. The Cox regression was performed to screen factors associated with recurrence of endometrial cancer. Based on the cut-off value of Ki67, the patients were divided into two groups, and the differences of clinicopathological parameters between the two groups were compared. RESULTS: The receiver operating characteristic curve showed that the optimal cut-off value of Ki67 for predicting recurrence of patients with stages I–II endometrial cancer was 38%. The multivariate Cox regression analysis demonstrated that the histotypes (P=0.012), myometrial invasion (P=0.014), cervical stromal invasion (P=0.001), Ki67 (P=0.002), estrogen receptor (ER) (P=0.045) and P53 (P=0.032) were significant prognostic predictors for recurrence of endometrial cancer. The recurrence-free survival and the disease-specific survival of patients in the high-Ki67 group (Ki67 ≥38%) were much lower than those in the low-Ki67 group (Ki67 <38%) (P=0.000, P=0.001, respectively). Among the 118 patients with early low-risk endometrial cancer who did not receive adjuvant treatment after surgery, the recurrence-free survival of patients in the high-Ki67 group was also lower than those in the low-Ki67 group (P=0.000). CONCLUSION: The Ki67 was demonstrated to be a useful prognostic factor in patients with stages I–II endometrial cancer, and the Ki67 labeling index 38.0% was optimal cut-off value for predicting recurrence.