Indium-111-pentetreotide scintigraphy and somatostatin receptor subtype 2 expression: New prognostic factors for malignant well-differentiated endocrine tumors

Purpose Well-differentiated metastatic endocrine carcinomas are difficult to manage because of variable disease outcome. New prognostic factors are required. These tumors overexpress somatostatin receptors (sst), implying the use of somatostatin analogs for tumor localization by somatostatin receptor scintigraphy using indium-111-pentetreotide (In-111-pentetreotide) and for medical treatment. The aim of the present study was to evaluate the correlation between In-111-pentetreotide scintigraphy, sst receptor expression, and prognosis. Patients and Methods Between 1994 and 2002, 48 consecutive patients with well-differentiated endocrine carcinomas and a negative In-111-pentetreotide scintigraphy were retrospectively paired according to sex, age, and tumor localization with 50 patients with well-differentiated endocrine carcinomas and a positive tracer uptake at In-111-pentetreotide scintigraphy. Overall survival and expression of sst1 to sst5 receptors by immunohistochemistry were assessed. Results The lack of tracer uptake at the In-111-pentetreotide scintigraphy seemed to be a poor prognostic factor (P=.007) for overall survival by Kaplan-Meier test and in multivariate analysis; age and absence of clinical secretory syndrome also seemed to be poor prognostic factors. The tracer uptake (positive In-111-pentetreotide scintigraphy) correlated with the tumor expression of somatostatin receptor sst2 (P<.001) but not with that of sst1, sst3, sst4, or sst5. In a bivariate analysis, lack of sst2 expression also significantly correlated with poor prognosis. Conclusion We demonstrate the prognostic value of In-111-pentetreotide scintigraphy in well-differentiated malignant endocrine tumors. In these tumors, sst2 somatostatin receptor expression correlates with both tracer uptake and a better prognosis.