OR27-2 11C-Methionine PET-CT co-registered with volume MRI identifies residual functioning tumour in acromegaly

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: OR27-Pituitary: Acromegaly and Prolactinoma
Sunday, June 16, 2013: 11:15 AM-12:45 PM
Presentation Start Time: 11:30 AM
Room 135 (Moscone Center)
Olympia Koulouri*1, Narayanan Kandasamy1, Carla M Moran1, V Krishna K Chatterjee1, David Halsall2, Hk Cheow3, Nagui Antoun3, Andrew Hoole3, Neil Burnet1, Neil Donnelly3, Richard Mannion3, John Pickard1 and Mark Gurnell1
1University of Cambridge & Addenbrooke's hospital, Cambridge, United Kingdom, 2University of Cambridge & Addenbrooke's hospital, 3Addenbrooke's hospital, Cambridge, United Kingdom
Although MRI remains the investigation of choice for pituitary imaging, it does not reliably identify all secretory microadenomas, and cannot always discriminate residual tumour from post-surgical change following hypophysectomy. We hypothesised that (i) imaging with the PET ligand 11C-methionine, which is taken up at sites of peptide/protein synthesis, would permit more reliable identification of functioning pituitary adenoma, and (ii) co-registration of PET-CT with volume MRI would yield more accurate anatomical localisation of 11C-methionine uptake.

We studied subjects with acromegaly in whom MRI had identified possible residual tumour following transsphenoidal surgery (TSS). We deliberately chose patients with acromegaly to allow correlation of radiological findings with clinical and biochemical markers of disease activity.

In three patients with suspected residual tumour on post-operative MRI, but in whom clinical and biochemical assessment confirmed remission, 11C-Methionine PET-CT-MRI showed no corresponding pathological tracer uptake. In contrast, in three patients with persistent active acromegaly following surgery, 11C-Methionine PET-CT-MRI demonstrated tracer uptake at the site of suspected residual tumour, which was confirmed at repeat TSS in one patient (the other two are awaiting surgery). In another patient, who elected to be treated with primary medical therapy, but in whom adequate control was not achieved despite somatostatin analogue and GH antagonist therapy, MRI revealed only a thin rim of tissue lining an enlarged pituitary fossa. However, 11C-Methionine PET-CT-MRI demonstrated focal tracer uptake, which was confirmed at subsequent surgery to be due to a strongly positive GH-staining somatotroph adenoma.

Our preliminary findings suggest that 11C-Methionine PET-CT co-registered with MRI is a useful adjunct for identifying functioning residual pituitary tumour when MRI appearances are inconclusive. As peptide/protein synthesis is a common property of all pituitary tumours (including so-called non-functioning pituitary adenomas) it is likely that 11C-Methionine PET-CT-MRI will find application in all tumour subtypes.

Disclosure: MG: Researcher, Ipsen, Speaker, Novartis Pharmaceuticals. Nothing to Disclose: OK, NK, CMM, VKKC, DH, HC, NA, AH, NB, ND, RM, JP

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm