title: Receptor imaging with 111In-pentreotide and 123I-methoxybenzamide, and inhibition tests with octreotide and bromocriptine of mixed growth hormone/prolactin-secreting pituitary tumors.
abstract: We have performed pituitary scintigraphy with 111In-pentreotide (OCT), a somatostatin analogue, and with metoxybenzamide (IBZM) by 123I-IBZM in two patients affected by mixed growth hormone/prolactin-secreting pituitary tumors. Short-term growth hormone (GH) inhibition by a single injection of OCT (100 micrograms s.c.), and short-term prolactin (PRL) inhibition by oral administration of 2.5 mg of bromocriptine (BCR), were also performed in both patients. The first patient, a 26 year old man, showed intense tumor uptake of 123I-IBZM scintigraphy, whereas 111In-OCT scintigraphy showed moderate tumor uptake. Five hours after the BCR inhibition test, a fall of 83% in PRL plasma levels (from 8,336 micrograms/L to 1,417 micrograms/L), and of 91.6% in GH plasma levels (from 39.5 micrograms/L to 3.3 micrograms/L) were observed. OCT inhibition test suppressed GH plasma levels from 36 micrograms/L to 3.5 micrograms/L. The patient was submitted to treatment with BCR and OCT. A dramatic shrinkage of the tumor was seen after six months of therapy. The lesion disappeared one year after the start of therapy. The second patient, a 64 year old man, showed intense uptake at 111In-OCT scintigraphy, while 123I-IBZM uptake was not observed. A test dose of BCR resulted in an acute fall of PRL (from 145 micrograms/L to 118 micrograms/L), but not of GH. A test dose of OCT decreased the GH plasma level from 61 micrograms/L to 4.5 micrograms/L. The patient was submitted to treatment with BCR and OCT that resulted in a computed tomography and magnetic resonance imaging decrease of 45% of tumor volume one year after the start of therapy. Our results suggest that both suppression tests with OCT and BCR, and scintigraphic studies in vivo with 123I-IBZM and 111In-OCT can be predictive for the effectiveness of therapies with dopamine agonists and/or SS-analogs in patients with mixed PRL/GH-secreting pituitary tumors. Further studies are required to evaluate the role of suppressive tests in selecting patients for appropriate clinical treatments.
authors.affiliation: Department of Onco-Haematology, Cardarelli Hospital, Naples, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Panza
authors.forename: P F
authors.initials: PF
authors.lastname: Rambaldi
authors.forename: C
authors.initials: C
authors.lastname: Battista
authors.forename: G
authors.initials: G
authors.lastname: Ambrosio
authors.forename: G L
authors.initials: GL
authors.lastname: Cascini
authors.forename: F
authors.initials: F
authors.lastname: Schillirò
authors.forename: L
authors.initials: L
authors.lastname: Mansi
mesh_terms: D000328:Adult; D001549:Benzamides / Q000493:pharmacokinetics; D001971:Bromocriptine / Q000493:pharmacokinetics; D003287:Contrast Media / Q000493:pharmacokinetics; D013006:Growth Hormone / Q000378:metabolism; D006801:Humans; D007205:Indium Radioisotopes; D007457:Iodine Radioisotopes; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000493:pharmacokinetics; D010911:Pituitary Neoplasms / Q000000981:diagnostic imaging*; D011388:Prolactin / Q000378:metabolism; D011759:Pyrrolidines / Q000493:pharmacokinetics; D011877:Radionuclide Imaging; D014054:Tomography
chemical_list: D001549:Benzamides; D003287:Contrast Media; D007205:Indium Radioisotopes; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D001971:Bromocriptine; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide; D011388:Prolactin; D013006:Growth Hormone; D015282:Octreotide