Treatment with High Dose [¹¹¹In-DTPA-D-PHE¹]-Octreotide in Patients with Neuroendocrine Tumors: Evaluation of Therapeutic and Toxic Effects

Abstract

Carcinoid tumors and endocrine pancreatic tumors often express somatostatin receptors (sst). Tumor spread may be visualized by sst scintigraphy using [¹¹¹In-DTPA-D-Phe¹]-octreotide. In this study, tumor targeting therapy with [¹¹¹In-DTPA-D-Phe¹]-octreotide at high doses (6 GBq every third week) was used to treat patients with sst-expressing tumors. Five patients entered the protocol and three were evaluable for response, while all could be evaluated for toxicity. Two patient responded with a significant reduction in tumor markers (>50%). The third patient showed increasing levels of tumor markers. Side effects were expressed as depression of bone-marrow function. In one patient a grade 4 reduction in platelet count was observed requiring several thrombocyte transfusions. In another two patients platelet counts decreased significantly. We conclude that treatment with [¹¹¹In-DTPA-D-Phe¹]-octreotide can be used in patients with neuroendocrine tumors but blood parameters have to be carefully monitored to avoid severe side effects.