Risk Classification using the Ki-67 Labeling Index for Surgically-Treated Gastric Gastrointestinal Stromal Tumors

BACKGROUND/AIMS: Adjuvant treatment with imatinib mesylate (IM) improves survival of patients with a high risk of recurrence of gastrointestinal stromal tumors (GISTs). However, the optimal adjuvant treatment strategy remains unknown. Thus, this study aimed to identify patients who do not require adjuvant IM treatment using the Ki-67 labeling index (LI).

METHODOLOGY: The Ki-67 LI was calculated in 59 patients with gastric GISTs. A new risk classification using the Ki-67LI and tumor size was established using cut-off values determined by receiver operating characteristic analysis. This Ki-67 classification was compared with the modified Fletcher classification (MF).

RESULTS: The best cut-off values for the Ki-67LI and tumor size were 8.6% and 80 mm, respectively. According to the MF, 42, 10, and 7 patients were categorized as low, intermediate, and high risk, respectively, while the Ki-67 classification rated 38, 17, and 4 patients as low, intermediate, and high risk, respectively. The 7 patients classified as high risk by MF were graded high risk (4 patients) and intermediate risk (3 patients) by the Ki-67 classification. Recurrence was not observed in patients classed intermediate risk by the Ki-67 classification.

CONCLUSIONS: The Ki-67 classification is helpful for identifying patients for whom adjuvant IM treatment is not necessary.