Is proliferative index (Ki-67) useful to stratify patients (pts) with G2 gastroenteropancreatic neuroendocrine tumors (GEP-NETs)? Clinicopathologic correlation

255 Background: Grade 2 (G2) Neuroendocrine tumors (NETs), of the digestive tract is a heterogeneous group of tumors. Several treatment options including chemotherapy and target therapy are available, but there is a lack of prospective trials assessing the role of pronostic factors in this population. Aim(s): to analyze prognostic factors and clinical characteristics in a population of patients with G2 GEP-NETs. To determine the role of ki 67 in the stratification of G2 population. Methods: Study population was obtained from our prospective database (Argentum Group). Survival was estimated using the Kaplan-Meier method and compared between Ki-67 quartiles using the log-rank test. Value of Ki-67 to discriminate mortality was assesed with a ROC curve analysis Results: 144 pts were evaluated. Mean age 54.9, 46.7% male. 102 (70.8%) with metastatic disease, mainly hepatic in 97 pts. (67.4%). 67.9 % underwent surgery. 34% received chemotherapy, and 10.9% target therapy. Median Ki-67 value was 6 (IQR 4-10), ROC curve=0.62 (95% CI 0.53 a 0.72 p=0.021. cut-off: 6.5 (sensitivity 62.2%, specificity 57.7%). Median survival was 97, 67, 51 and 27 months according stratification by quartile (p.001), 45 events (31.7%). Conclusions: Our results suggest that in the heterogenous G2 GEP-NETs there are significant differences in survival. This study was underpowered to detect differences between Ki-67 quartiles, we detected that chemotherapy was mostly used in the higher quartiles.