J Neurol Surg A Cent Eur Neurosurg 2014; 75 - p24
DOI: 10.1055/s-0034-1383760

18Fluoroethyl-L-tyrosine PET for Localization of Cushing Adenoma

S. Berkmann 1, F. Jüngling 2, A. K. Borm 3, B. Müller 3, J. Fandino 1, H. Landolt 1
  • 1Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland
  • 2Department of Nuclear medicine, Claraspital Basel, Basel, Switzerland
  • 3Department of Endocrinology, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland
  • 4Department of Endocrinology, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland
  • 5Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland
  • 6Department of Neurosurgery, Kantonsspital Aarau, Aarau, Switzerland

Objective: 11-C-methionine positron emission tomography (MET PET) was described as a tool for localization of Cushing adenoma. Due to the low half-life of 11-C(20.38 minute) it is only available in few centers. The use of the more commonly available 18-fluoroethyl-L-tyrosine PET (FET PET) has not been described in Cushing’s disease. The goal of this prospective trial is to analyze the impact of FET PET on localization of Cushing adenoma and on surgical cure rates.

Methods: Six patients with Cushing’s disease admitted for transsphenoidal tumor resection were included to assess feasibility and evaluate preliminary results. The tumor localizations were evaluated by FET PET-CT and MET PET-CT and compared with 3.0T MRI scans and - if applicable - to sinus petrosus sampling findings. In a second step, the fused FET PET images were used for intraoperative navigation and compared with the operative findings during transsphenoidal tumor resection (detection of tumor by the surgeon, histological results of biopsies). In a third step, the endocrinological outcome was assessed during a minimum follow-up time of 6 months.

Results: All patients underwent FET PET and MET PET scans within one month before surgery. The pattern of tracer accumulation did not vary significantly between the two methods. For intraoperative navigation, the PET images were fused to CT scans. On MRI scans, the tumors were visible in 3 (50%) cases with maximum diameters from 3 to 8mm (mean 5mm). Sinus petrosus sampling was performed in 4 cases and correlated with the side of maximum tracer uptake on PET scans in 2 patients. Intraoperative visualization of the tumors correlated with the point of maximum tracer accumulation on the PET scans in all cases. Immunohistological staining showed ACTH-producing pituitary adenoma cells in 5 cases. Five (83%) patients were free of Cushing’s disease during a mean follow-up of 14 months. A 50 years-old female patient presented with persistence of ACTH excess and was revised in vain by hemihypophysectomy. Ultimately she underwent bilateral adrenalectomy. There were no adverse events due to PET scanning or surgery.

Conclusions: Judging from these preliminary results, FET-PET may be a safe non-invasive method for localization of small pituitary adenoma in patients with Cushing’s disease. PET scans fused to CT images for intraoperative navigation may be a useful tool for the surgeon.