Human biodistribution of [111In]diethylenetriaminepentaacetic acid-(DTPA)-D-[Phe1]-octreotide and peroperative detection of endocrine tumors.

Requisites for preoperative and intraoperative tumor localization with [111In]diethylenetriaminepentaacetic acid-D-[Phe1]-octreotide scanning were explored in 23 patients with endocrine tumors (15 carcinoids, 4 insulinomas, and single cases of gastrinoma, medullary thyroid carcinoma, aldosteronoma, and paraganglioma). The patients were subjected to Octreoscan single photon emission computed tomographic examination prior to surgery and well counter investigation of nuclide uptake in tumors and normal tissues sampled at surgery. Somatostatin receptor-positive tumors demonstrated efficient nuclide accumulation with mean tumor:blood radioactivity ratios of 180-370 (for carcinoids and insulinoma), compared with tissue:blood ratios of 302 for spleen, 42 for liver, and < 10-15 in other normal tissues (pancreas, small intestine, and mesenteric fat). Inefficient preoperative visualization of lesions was related to inconspicuous size, as for primary intestinal carcinoids, tiny liver metastases, and a single small insulinoma. High background activity, pronounced tumor fibrosis, and meager accumulation of tracer also interfered with visualization. Tumor deposits in organs with low background activity (such as carcinoid mesenteric metastases and endocrine pancreatic tumors) were generally most readily detected. Intraoperative investigations with hand-held gamma detector probes were disturbed by obvious high background activity. These investigations revealed two preoperatively unrecognized primary intestinal carcinoids, which, however, were both palpable during surgery. These studies, therefore, had little impact on the surgical strategy.