title: Results of somatostatin receptor scintigraphy do not predict pituitary tumor volume- and hormone-response to ocreotide therapy and do not correlate with tumor histology.
abstract: The value of somatostatin receptor scintigraphy (SRS) to predict the effect of somatostatin analog therapy on pituitary adenomas is not clear, due to the use of different radiopharmaceuticals (123I-Tyr3-octreotide and 111In-pentetreotide) and the small number of patients in previous studies. We used 111In-pentetreotide scintigraphy in 49 patients in order to (i) correlate SRS results with basal tumor volume as well as volume- and hormone-response to 3 months of octreotide therapy (Oct-Tx). (ii) identify tumor remnants after incomplete surgery and (iii) evaluate any correlation with immuno histology. Twenty-five patients had a GH-secreting adenoma (GH-A, 15 prior to intended surgery, 10 with persistent/recurrent disease after previous therapy). Twenty-four patients had a clinically non-functioning adenoma (NF-A). For SRS, planar and single photon emission computer tomographic images (SPECT) were recorded 4 h and 24 h post injection. SRS grading was as follows: GO, no uptake: G1, uptake comparable to normal pituitary; G2, increased uptake: G3, very intense uptake. G2/3 was seen in 8/25 GH-A and in 12/24 NF-A. Pretreatment tumor volume (magnetic resonance imaging (MRI) tended to be related to 111In-pentetreotide uptake in GH-A with a tumor visible on MRI (G0/1 (n = 10) vs G2/3 (n = 8): 3.6 +/- 1.9 vs 10.5 +/- 6.5 cm3 (mean +/- S.E.), P = 0.051), but not in NF-A (G0/1 (n = 12) vs G2/3 (n = 12): 17.0 +/- 10.1 vs 14.3 +/- 3.6 cm3). SRS did not identify a tumor remnant in the 7 MRI-negative patients with persistent post-operative acromegaly. Basal GH (6-h profile) and IGF-1 in GH-A did not correlate with SRS results (G0/1 (n = 17) vs G2/3 (n = 8), GH: 32.3 +/- 18.2 vs 29.3 +/- 7.4 micrograms/l IGF-I: 851 +/- 80 vs 1038 +/- 153 micrograms/l). During Oct-Tx of GH-A neither tumor shrinkage nor GH suppression was related to SRS results. In 6 NF-A classified as gonadotropinomas (by their plasma glycoprotein hormone or alpha-subunit concentrations, basally and/or in response to TRH) 111In-pentetreotide uptake was not different from that of the non-gonadotropin/non-secreting adenomas. SRS results were not related to the immunohistological subtype in 22 GH-A (monohormonal mixed somatotrope/lactotrope, plurihormonal) or in 22 NF-A (null-cell adenomas, gonadotropinomas silent hormonal adenomas). We conclude that 111In-pentetreotide SRS reflects tumor volume poorly in GH-A and not at all in NF-A. It does not predict the effect of Oct-Tx on the volume of both GH-A and NF-A, nor on the GH concentration in GH-A. 111In-pentetreotide SRS is unable to identify post-operative tumor remnants not visible on MRI.
authors.affiliation: Department of Endocrinology, Klinikum Benjamin Franklin, Freie Universität, Berlin, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Plöckinger
authors.forename: M
authors.initials: M
authors.lastname: Bäder
authors.forename: W
authors.initials: W
authors.lastname: Hopfenmüller
authors.forename: W
authors.initials: W
authors.lastname: Saeger
authors.forename: H J
authors.initials: HJ
authors.lastname: Quabbe
mesh_terms: D000236:Adenoma / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000188:drug therapy*; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007986:Luteinizing Hormone / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000627:therapeutic use*; D010902:Pituitary Gland / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D010911:Pituitary Neoplasms / Q000737:chemistry* / Q000000981:diagnostic imaging / Q000188:drug therapy*; D011237:Predictive Value of Tests; D011388:Prolactin / Q000097:blood; D011877:Radionuclide Imaging; D017481:Receptors, Somatostatin / Q000032:analysis*; D012680:Sensitivity and Specificity; D013972:Thyrotropin / Q000097:blood; D014057:Tomography, X-Ray Computed
chemical_list: D000970:Antineoplastic Agents; D017481:Receptors, Somatostatin; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013006:Growth Hormone; D015282:Octreotide