A Ki-67/CD34 prognostic model for risk stratification in resected gastrointestinal stromal tumors.

Abstract

e23515 Background: Accurate risk stratification is essential for guiding postoperative adjuvant therapy in resected gastrointestinal stromal tumors (GIST). Traditional Joensuu criteria rely mainly on mitotic count, together with tumor size and primary site. While immunohistochemistry is routinely used for diagnosis, integrating biomarkers into prognostic assessment may improve identification of patients at high risk of recurrence after curative resection. We developed a prognostic model incorporating a proliferation marker (Ki-67) and a vascular marker (CD34) to improve postoperative risk stratification. Methods: We retrospectively collected 634 patients with localized GIST who underwent curative resection at the National Cancer Center of China. The primary endpoint was disease-free survival (DFS). A multivariable Cox regression model including Ki-67 index, CD34 expression, tumor size, and sex was developed; mitotic count and tumor site were evaluated for inclusion. Discrimination was compared with the modified Joensuu criteria using Harrell’s concordance index (C-index) and log-rank tests. Results: In this cohort, the Joensuu criteria showed limited DFS separation between intermediate- and high-risk groups (log-rank P=0.17). In multivariable analysis, Ki-67 index and CD34 positivity were independent prognostic factors. Mitotic count and tumor site were evaluated but were not retained in the final multivariable model. The integrated model achieved a C-index of 0.766 (95% CI, 0.632–0.877), higher than the Joensuu criteria (C-index 0.694; 95% CI, 0.573–0.795). In multivariable Cox regression for DFS (Table), higher Ki-67 index and larger tumor size were associated with increased risk, whereas CD34 positivity and female sex were protective. The model provided improved discrimination among higher-risk patients, with significant separation between intermediate- and high-risk groups (P=0.002), whereas DFS was similar between low- and intermediate-risk groups (P=0.86). Conclusions: A prognostic model integrating Ki-67 and CD34 may refine DFS risk stratification after GIST resection, particularly at the intermediate- versus high-risk boundary where standard criteria show limited discrimination. This approach may support more tailored selection of patients for postoperative adjuvant therapy. Multivariable analysis of factors associated with DFS. Variable HR 95% CI P value Ki-67 index (per 1% increase) 1.04 1.01-1.07 0.007 Tumor size (per 1 cm increase) 1.08 1.01-1.16 0.019 CD34 positive (vs negative) 0.36 0.16-0.81 0.014 Female (vs male) 0.37 0.17-0.81 0.013