Somatostatin receptor (SSTR) expression and proliferative index (Ki 67) in 100 patients (pts) with gastroenteropancreatic neuroendocrine tumors (GEP-NETs): Clinical-pathological correlation.

Abstract

e14598 Background: Somatostatin receptor expression (SSTR), mainly subtypes 2 and 5, is a feature of well differentiated GEP-NETs. Such expression has a prognostic and predictive value for the use of somatostatin analogs.Ki 67, present during the cycle phases (G1, S, G2 y M) is a nuclear antigen associated with cell proliferation. The correlation between both clinical and pathological factors is under active investigation in patients with GEP-NETs. Methods: An analysis including 100 patients in the database of the Argentum Group was performed. Consecutive patients were included during the 2006-2007 period. In all cases, a centralized revision of the sample was conducted for diagnosis confirmation.The study of SSTR receptors in tissue and Ki67 was conducted using IHQ.The Kaplan-Meier method was used to analyse survival. Log-rank test was used for the comparative analysis of the variables of interest. Results: The expression of at least one of the SSTRs 2 (a) or 5 was found in 86% and 62% of cases respectivevly in this population. The univariate analysis showed significant differences in the expression of SSTR2 (a) but not in the expression of SSTR 5.The expression of the proliferative index (Ki 67) was associated with significant differences in relation to OS at 5 years, 84% (Ki 67 under or equal to 2%), 66% (Ki 67 between 3 and 15%) and 13% (Ki 67 over 15%). The OS at 5 years in patients with SSTR 2/5 positive and Ki 67 under 2% was 86%, 64% in pts. with SSTR 2/5 positive and Ki 67 over 2% and 20 % in pts. with SSTR 2/5 negative, independent Ki 67 (p .0023). Conclusions: The expression of at least one of the SSTRs 2 (a) or 5 was found in 86% and 62% of cases respectivevly in this population. In the population with GEP-NETs under study, a subgroup of patients with a better prognosis was identified in association with the expression of SSTR 2/5 and Ki67 below 2%. The assessment of SSTR 2(a) and 5 in tissues, together with the study of the proliferative index are a useful tool for prognosis assessment in these patients.