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

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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.