Intraoperative gamma detection reveals abdominal endocrine tumors more efficiently than somatostatin receptor scintigraphy

BACKGROUND. [ 111 In]-diethylenetriamine pentaacetic acid [DTPA)-D-[Phe]-octreotide (OctreoScan), Mallinckrodt Medical, Petten, The Netherlands), combined with single photon emission computed tomography (SPECT), has limited possibilities to detect small abdominal endocrine tumors. This study explores the efficacy of OctrenScan and a newly developed handheld gamma detector probe (H-probe2) for the localization of neuroendocrine abdominal tumors. METHODS. Twenty-one patients with endocrine pancreatic or midgut carcinoid tumors were given 100-200 megabecquerels (MBq) [ 111 In] -DTPA-D-Phe 1 ]-octreotide and underwent preoperative SPECT examination, after which time surgery was undertaken within 24-48 hours. Intraoperatively the radioactivity of tumors and normal tissues was measured with the H-probe2 connected to a portable personal computer. Resected intestinal specimens of ten patients with carcinoid tumors were examined by gamma camera ex vivo. Biopsies of all tumors subsequently were investigated in a wellcounter and by routine histopathology. RESULTS. Disregarding liver metastases, a total of 34 of 60 abdominal tumors were detected by SPECT; however, SPECT failed to visualize any tumor 5 mm. In the wellco inter the H-probe2-detected tumors exhibited 4.7-157.7 times higher radionuclide uptake than the surrounding normal tissues. The gamma camera analysis detected 68% of tumors in the resected specimens. CONCLUSIONS. The intraoperative H-probe2 examination provided substantial improvement in the detection of small endocrine lesions accumulating 111 InDTPA-D-Phe-octreotide and all lesions with a size > 5 mm in greatest dimension could be identified.