Prognostic value of Ki67 index in gastrointestinal stromal tumors.

BACKGROUND Ki67 index is one of the most important immunocytochemical markers of proliferation in tumors, but the criterion of Ki67 index in GISTs was not well-defined yet. Our study aims to fully evaluate the prognostic value of Ki67 index in GIST patients and efficiency of imatinib adjuvant therapy. METHODS Clinicopathological data were confirmed by pathological diagnosis and clinical recorders. Recurrence-free survivals (RFS) were evaluated in 418 GIST patients (370 cases only taken the surgery and 48 high-risks taken imatinib adjuvant therapy after R0 resection). RESULTS Two cutoff levels of Ki67 index (>5 and >8%) were established in our study through statistical analysis. Ki67 index (≤5, 6-8 and >8%) is an independent prognostic factor for RFS of GIST patients. Ki67 index>8% can precisely sub-divide high-risk GISTs effectively with different outcomes, and high-risk patients with Ki67 index>8% showed a poorer prognosis even with imatinib adjuvant therapy. CONCLUSION Ki67 index is an effective complementation of modified NIH criteria in predicting the prognosis of GISTs, and Ki67 index>8% may act as an unfavorable factor for imatinib adjuvant therapy.