Prospective assessment of 11C-Methionine PET-MRI performance to localize corticotroph pituitary microadenomas

A. Flaus*a (Dr), E. Levigoureuxb (Dr), F. Cottonc (Prof), N. Costesd (Dr), I. Meridad (Dr), H. Lasollee (Dr), A. Vasiljevicf (Dr), E. Jouanneaug (Prof), G. Raverote (Prof), C. Bournauda (Dr)

a Hospices Civils de Lyon, Nuclear Medicine Department, Lyon, FRANCE ; b Hospices Civils de Lyon, Pharmacy Department, Lyon, FRANCE ; c Hospices Civils de Lyon, Radiology Department, Lyon, FRANCE ; d Cermep, Lyon, FRANCE ; e Hospices Civils de Lyon, Endocrinology Department, Lyon, FRANCE ; f Hospices Civils de Lyon, Laboratory Medicine and Pathology Department, Lyon, FRANCE ; g Hospices Civils de Lyon, Neurosurgery Department, Lyon, FRANCE

* anthime.flaus@gmail.com

Introduction: Reliably identifying the localization of a corticotroph adenoma increases surgical outcome. Nevertheless, it remains challenging since pituitary MRI accuracy is around 75%. Retrospective studies suggested that functional imaging with 11C-methionine (MET) PET combined with MRI could improve localization of corticotroph microadenomas (1,2). The aim of this study was to prospectively assess the performance of 11C-MET PET-MRI to localize pituitary ACTH-secreting microadenomas.

Material and methods: We included patients with biologically confirmed Cushing disease and typical microadenoma on MRI or petrosal sinus sampling indicative of corticotroph adenoma for which surgery was indicated. Patients were naive of pituitary targeted treatment or previous surgery. All patients underwent 11C-MET PET-MRI (Biograph mMR Siemens). The gold standard was the anatomopathological analysis of the surgical specimen. PET and MRI were independently reviewed by 2 nuclear physicians and a radiologist blinded of clinical information. If adenoma was identified, its localization was classified as left, right or median.

Results: 30 patients were included. Pathology confirmed pituitary adenomas in 28 patients (93.3%), localization was right for 12 (40%), left for 11 (36.7%) and median for 5 (16.7%). Adenoma was identified in 28 (93.3%) MRI and 27 (90%) PET. Pituitary localization in MRI and PET were respectively right for 11 (36.7%) vs 9 (30%), left for 12 (40%) vs 11 (36.7%) and median for 5 (16.7%) vs 7 (23.3%). MRI and PET sensitivities were 76.7% and 37.7% (p<0.05). Short-term follow-up revealed 86,7% surgical cure with low cortisol levels and normal cortisol function in 20 (66.7%) and 6 (20%) patients respectively and persistent disease in only 4 (13.3%).

Discussion: Our result did not confirm the additional value of 11C-MET PET to localize corticotroph adenoma. As suggested in Koulouri’s study (2) additional post processing of 11C PET images may be necessary to improve the diagnostic performance of 11C-MET PET-MRI, which in our experience was limited by the physiological uptake of the pituitary gland. Despite absence of formal preoperative image, surgical experience allowed a high cure rate in Cushing disease.

  1. Ikeda H, et al. JNS. 2010Apr;112(4):750-5.
  2. Koulouri O, et al. Eur. J. Endocrinol. 2015Oct;173(4):M107-20.

The author has declared no conflict of interest.