Dopamine agonist therapy of clinically non-functioning pituitary macroadenomas. Is there a role for 123I-epidepride dopamine D2 receptor imaging?
OBJECTIVE
Clinically non-functioning pituitary adenomas (NFPAs) can express functional dopamine D2 receptors. Therapy with dopamine (DA) agonists may result in a NFPA size reduction. However, DA agonist-sensitive and -resistant NFPAs are clinically indistinguishable. We have studied the correlation between in vivo imaging of D2 receptors using (123)I-epidepride and the radiological response of NFPA to DA in 18 patients.


METHODS
Patients were treated with either cabergoline (1-2 mg/week) or quinagolide (150-300 mug/day) for a mean period of 89.7 months (range, 34-187 months).


RESULTS
Pituitary uptake of (123)I-epidepride varied from slight uptake classified as grade 0 to very high classified as grade 3. Grade 0 uptake was found in four patients; grade 1 in three; grade 2 in ten, and grade 3 in one. NFPA stabilization or shrinkage with DA agonist therapy showed no significant difference between grade 0, 1, and 2 tumors (mean tumor stabilization or shrinkage: 31, 30, and 36% respectively). However, when we considered a decrease in tumor size ranging from 0 to 20% as tumor stabilization and >20% decrease in tumor size as true shrinkage, one out of four NFPAs with grade 1 uptake, two out of three with grade 1 uptake, and eight out of ten with grade 2 uptake showed tumor shrinkage.


CONCLUSIONS
In conclusion, there is limited clinical usefulness of dopamine D2 receptor imaging for predicting the clinical efficacy of DA agonist in selected patients with NFPAs. DA agonist therapy in NFPAs can result in tumor stabilization and shrinkage.
de Herder
Wouter W
WW
Department of Internal Medicine, Section of Endocrinology, Erasmus MC, S Gravendijkwal 230, 3015 CE Rotterdam, The Netherlands. w.w.deherder@erasmusmc.nl
Reijs
Ambroos E M
AE
Feelders
Richard A
RA
van Aken
Maarten O
MO
Krenning
Eric P
EP
Tanghe
Hervé L J
HL
van der Lely
Aart-Jan
AJ
Kwekkeboom
Dik J
DJ
D000236:Adenoma / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000634:Aminoquinolines / Q000627:therapeutic use; D001549:Benzamides; D000077465:Cabergoline; D018491:Dopamine Agonists / Q000627:therapeutic use*; D004873:Ergolines / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2 / Q000032:analysis*; D015899:Tomography, Emission-Computed, Single-Photon
D000634:Aminoquinolines; D001549:Benzamides; D018491:Dopamine Agonists; D004873:Ergolines; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; C063525:epidepride; C046650:quinagolide; D000077465:Cabergoline