(dtpa-phe(1))-octreotide and Neuroectodermal-Tumors

Scintigraphy with [111In-DTPA-D-Phe]-octreotide is a recently developed technique for imaging somatostatin receptors in many neuroendocrine tumors. A good correlation between high [111In-DTPA-D-Phe]-octreotide uptake and the response to octreotide therapy has been proved in TSH- and GH-secreting pituitary adenomas, while few and conflicting scintigraphic data on somatostatin receptors in non-functioning tumors have been reported in the literature. The present study presents the results obtained with [111In-DTPA-D-Phe]-octreotide scintigraphy in thirteen patients with GH-secreting pituitary adenoma, four patients with inappropriate TSH-secretion and twelve patients with non-functioning pituitary adenoma. Twelve out of the 13 patients with GH-secreting pituitary adenomas had a positive scan; moreover, in 5/6 patients with a GH-secreting microadenoma (tumor size range 5-8 mm) a positive scan was found. Two TSH-secreting macroadenomas had a positive scan while a negative scan was obtained for a TSH-secreting pituitary microadenoma and in a patient with non-neoplastic, inappropriate secretion of TSH. Finally, only 2/12 patients with non-functioning pituitary adenoma showed a positive scan. In conclusion, [111In-DTPA-D-Phe]-octreotide scintigraphy is a useful tool to confirm the presence of somatostatin receptors in selected patients with GH- and TSH-secreting pituitary adenoma. The role of [111In-DTPA-D-Phe]-octreotide scintigraphy in non-functioning pituitary tumors remains to be established, but it could be useful for octreotide treatment in patients who refuse surgery or who are poor surgical candidates.

Topics: Adenoma; Adult; Aged; Aged, 80 and over; Antineoplastic Agents, Hormonal; Female; Human Growth Hormone; Humans; Indium Radioisotopes; Male; Middle Aged; Neuroectodermal Tumors; Octreotide; Pentetic Acid; Pituitary Neoplasms; Radiopharmaceuticals; Receptors, Somatostatin; Skull; Thyrotropin; Tomography, Emission-Computed, Single-Photon

The aim of this study was to use compartmental analysis as a theoretical tool to provide quantitative and unitary data for a more precise determination of 111In-OCT concentrations in a tumour site and various body organs. Five subjects (3 male and 2 female) with neoplasias were studied. Structural and parametric identification of the model was based on the plasma, urine, total body and ROI (soft tissue, spleen, kidney and tumour) activity values. The model was of the mammillary type with 5 compartments (blood, soft tissue, spleen, kidneys and urine) for the 4 patients with a negative scintiscan and 6 (blood, soft tissue, spleen, kidneys, urine and tumour) for the adenocarcinoma patient. Numerical constants were determined by running a best-fit procedure with the MINUIT minimisation program (CERN library) using a microVAX 3800 computer. The reliability of the models was also tested. 111In-OCT accumulates in the kidneys and spleen, from which it is slowly released into the blood. Elimination is via the urine at first rapidly, then more slowly. The maximum concentration in the tumour compartment is reached at 12-14 hours and remains almost constant.

Topics: Adenocarcinoma; Carcinoma, Small Cell; Computer Simulation; Female; Humans; Indium Radioisotopes; Kidney; Lung Neoplasms; Male; Metabolic Clearance Rate; Models, Biological; Models, Chemical; Neuroblastoma; Neuroectodermal Tumors; Octreotide; Pentetic Acid; Radiopharmaceuticals; Reproducibility of Results; Spleen; Tissue Distribution