ECE2015 Guided Posters Pituitary – Hypopituitarism (9 abstracts)
‘Pseudo-resistance' in macroprolactinomas treated with dopamine agonists; recognising delayed radiological response and a role for 11C-methionine PET-CT in guiding management
Andrew S Powlson 1 , Olympia Koulouri 1 , Andrea Steuwe 2 , Daniel Gillett 2 , Sarah Heard 2 , Andrew Hoole 3 , Miriam Scott 1 , Benjamin G Challis 1 , Nagui Antoun 4 , Heok K Cheow 4 , Richard J Mannion 5 & Mark Gurnell 1
1Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, UK; 2Department of Nuclear Medicine, Addenbrooke’s Hospital, Cambridge, UK; 3Department of Medical Physics, Addenbrooke’s Hospital, Cambridge, UK; 4Department of Radiology, Addenbrooke’s Hospital, Cambridge, UK; 5Department of Neurosurgery, Addenbrooke’s Hospital, Cambridge, UK.
Background: Endocrine Society guidelines classify macroprolactinomas as ‘resistant’ if there is failure to normalise prolactin, or to achieve radiological tumour shrinkage of >50%, on standard doses of dopamine agonist. In this context, escalation of treatment to maximal tolerable doses and/or referral for surgery is advised. However, we have recently observed several ‘discordant responders’, where tumour shrinkage lags significantly (>6 months) behind the biochemical response, but is ultimately achieved without treatment escalation.
Methods: i) A Pubmed search for ‘medical treatment of prolactinomas’ was performed & papers reporting discordance between biochemical and radiological responses identified and ii) We searched our pituitary database for patients treated locally over a 10-year period. A case where 11C-methionine PET-CT was used to guide management is described.
Results: From an initial return of 845 papers, 21 provided sufficient information, describing 340 patients, 92 of whom exhibited a discordant response. Of 89 macroprolactinomas in our local database, we identified 14 patients in whom prolactin normalised, but tumour shrinkage was <50% at >6 months after commencing treatment. One of these, a 36-year-old man (initial prolactin 14,123mU/l) achieved biochemical normalisation within eight weeks; however, despite continued prolactin suppression (28mU/l; 500mcg twice-weekly) at 12 months his tumour showed no reduction in size. Reassuringly, 11C-methionine PET-CT coregistered with MRI demonstrated a complete absence of tracer uptake in the ‘residual adenoma’. With this evidence, contrary to Endocrine Society Guidelines, cabergoline was reduced to 250mcg twice-weekly. 24-months later serum prolactin remained well-controlled (76 mU/l), and substantial (>50%) tumour shrinkage was evident on MRI.
Conclusions: These cases demonstrate that a delayed radiological response may be seen without further dose escalation, once biochemical normalisation has been achieved in prolactinomas; current guidelines may therefore inappropriately categorise such tumours as ‘dopamine agonist resistant’. Our literature and local database review suggests this may be an under-recognised phenomenon. Furthermore, the case described here highlights the utility of functional imaging in aiding management in such patients.
Article tools
My recent searches
My recently viewed abstracts
Authors
Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
© Bioscientifica 2024 |
Privacy policy |
Cookie settings
BiosciAbstracts
Bioscientifica Abstracts is the gateway to a series of products that provide a permanent, citable record of abstracts for biomedical and life science conferences.
Find out more