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

## TL;DR

This study shows that the Ki-67 labeling index can help identify non-high-risk gastrointestinal stromal tumor patients who are at higher risk of recurrence.

## Contribution

The study introduces a Ki-67 labeling index cutoff of 3.0% as a novel stratification tool for non-high-risk GISTs.

## Key findings

- A Ki-67 LI cutoff of 3.0% significantly predicted recurrence in non-high-risk GISTs.
- None of the non-high-risk patients with Ki-67 LI < 3.0% experienced recurrence.
- Recurrence rates were 26.9% for non-high-risk patients with Ki-67 LI ≥ 3.0%.

## Abstract

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.