The pituitary uptake of (111)In-DTPA-D-Phe1-octreotide in the normal pituitary and in pituitary adenomas

The aim of this study was to compare the pituitary (111)In-DTPA-D-Phe1-octreotide uptake measured in 49 patients subjected to the scintigraphy for SS-R expressing tumors not located in the sellar region with that measured in 38 patients with pituitary adenomas. The 87 subjects enrolled in this study were divided into two groups: the first included SSR-expressing tumors (SS-ET), 10 thymomas, 13 differentiated thyroid carcinomas, 4 carcinoids, 5 neuroendocrine tumors, 5 insulinomas, 6 melanomas, 2 renal carcinomas, 2 pheocromocytomas, and 2 parathyroid tumors, while the second included pituitary adenomas, 25 GH-secreting, 4 GH/PRL-mixed and 9 clinically nonfunctioning adenomas (NFA). Planar and single-photon-emission tomography images of the head were obtained 2-4 and 24 hours after the injection of 77-103 MBq of (111)In-DTPA-D-Phe1-octreotide and pituitary uptake was measured by the region of interest method. A 4 point score was used to grade the pituitary-to-blood (T-to-B) ratios: 0=negative; 1 =faint (T-to-B=3.5). In patients with pituitary adenomas, the percent suppression of GH and alpha-subunit levels after 6-12 months of octreotide treatment (0.3-0.6 mg/day) was correlated to T-to-B ratios. After 2-4 hr from injection, pituitary (111)In-DTPA-D-Phe1-octreotide uptake was moderate/intense in 2 out of 49 SS-ET (4%), 18 out of 29 acromegalics (62%) and 6 NFA (66.6%), while a faint uptake was detected in 4 SS-ET (8%), 8 GH-secreting adenomas (27.5%) and 3 NFA (33.3%). Negative scan was detected in the remaining 43 SS-ET (87.7%) and 3 GH-secreting microadenomas (10.3%). 24 hr after injection, pituitary (111)In-DTPA-D-Phe1-octreotide uptake was moderate/intense in SS-ET (10.2%), 21 GH-secreting adenomas (72.4%), and 9 NFA (100%) while a faint uptake was detectable in 15 SS-ET (30.6%), and 6 GH-secreting adenomas (20.7%). No uptake was visualized in 29 SS-ET, and 2 GH-secreting adenomas. By MRI a pituitary tumor was shown in the 2 SS-ET with early moderate tracer uptake. Normalization of circulating GH/IGF-I levels and suppression of alpha-subunit levels was achieved in 16 of 18 acromegalics (88.9%) and 5 of 6 NFA-bearing patients, respectively, with scan scored 2-3 at early images. Eleven acromegalics (37.9%) and 2 NFA (22.2%) displayed significant tumor shrinkage (> or =30% of baseline size) during long-term octreotide therapy. Both in GH-secreting and in NFA, a significant correlation was found between percent GH or alpha-subunit suppression after 6-12 months of octreotide therapy and T-to-B ratios both in early (r=0.626; p