Evaluation of the Ki-67 Labeling Index as a Prognostic Stratification Factor in Non-High-Risk Gastrointestinal Stromal Tumors

Aim This study aimed to evaluate the Ki-67 labeling index (LI) as a prognostic factor for recurrence in patients with non-high-risk gastrointestinal stromal tumors (GISTs), as defined by the modified NIH risk classification. Patients and methods In this retrospective study, 72 patients with GISTs who had undergone complete tumor resection and received no adjuvant therapy until recurrence were included. The Ki-67 LI and mitotic count were assessed in hotspot sections of each tumor. Results According to the modified NIH risk classification, 54 tumors were categorized as non-high-risk (very low-, low-, or intermediate-risk) and 18 as high-risk. During follow-up, recurrence occurred in seven (13.0%) non-high-risk cases and nine (50.0%) high-risk cases. Receiver operating characteristic analysis for recurrence identified an optimal Ki-67 LI cutoff of 3.0% for non-high-risk GISTs. Among non-high-risk cases, recurrence occurred in seven of 26 (26.9%) with Ki-67 LI ≥ 3.0%, whereas none of the 28 with Ki-67 LI < 3.0% experienced recurrence. Kaplan-Meier analysis of recurrence-free survival, stratified by this cutoff, showed significantly worse outcomes for the non-high-risk group with Ki-67 LI ≥ 3.0%. Conclusions These findings suggest that Ki-67 LI may serve as a useful stratification factor in patients with non-high-risk GISTs. In particular, applying Ki-67 LI stratification may help identify non-high-risk patients who require closer surveillance.