A comparative analysis of three positron emission tomography tracers in a patient with residual acromegaly

Linus Hesse; Daniel Gillett; James Macfarlane; Matthias Pirlich; Loreen Richter; Vanessa Hubertus; Peter Vajkoczy; Carolin Senger; Lukas Maurer; Strasburger Christian J.; Knut Mai; Guliz Acker; Mark Gurnell; Linus Haberbosch

doi:10.1530/endoabs.110.EP1208

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Endocrine Abstracts (2025) 110 EP1208 | DOI: 10.1530/endoabs.110.EP1208

ECEESPE2025 ePoster Presentations Pituitary, Neuroendocrinology and Puberty (220 abstracts)

A comparative analysis of three positron emission tomography tracers in a patient with residual acromegaly

Linus Hesse ^1,2,3 , Daniel Gillett ² , James Macfarlane ² , Matthias Pirlich ⁴ , Loreen Richter ^1,3 , Vanessa Hubertus ^3,5 , Peter Vajkoczy ^3,5 , Carolin Senger ^3,6 , Lukas Maurer ^1,3 , Christian J. Strasburger ^1,3 , Knut Mai ^1,3,7 , Güliz Acker ^3,5,6 , Mark Gurnell ² & Linus Haberbosch ^1,2,3

Author affiliations

¹Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health; Department of Endocrinology and Metabolism, European Reference Network on Rare Endocrine Diseases (ENDO-ERN), Berlin, Germany; ²Cambridge Endocrine Molecular Imaging Group, Institute of Metabolic Science, University of Cambridge, National Institute for Health Research Cambridge Biomedical Research Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom; ³Pituitary Tumor Center of Excellence at Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; ⁴Praxis Kaisereiche, Berlin, Germany; ⁵Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health; Department of Neurosurgery, Berlin, Germany; ⁶Charité CyberKnife Center, Department of Radiation Oncology, Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany; ⁷Department of Human Nutrition, German Institute of Human Nutrition Potsdam-Rehbrücke, Nuthetal, Germany

JOINT3416

Background: Molecular imaging is gaining importance in the localisation diagnostics of pituitary disease. However, the availability of tracers varies between different centres. The currently best evidence exists for the amino acid tracer ¹¹C-methionine (MET).¹⁸F-fluoroethyl-tyrosine (FET) has been reported as a potential alternative to MET with broader availability. While ⁶⁸Ga-DOTATOC (DOTATOC) shows high uptake in the normal pituitary gland, data is limited regarding uptake in adenomas.

Methods: Here we report a 35-year-old patient with residual acromegaly after two endoscopic transsphenoidal surgeries who had intolerable side effects under medical therapy and underwent DOTATOC-PET, FET-PET and MET-PET. All scans were undertaken in line with published PET acquisition references for each tracer.

Results: MET-PET and DOTATOC-PET identified two distinct foci of increased tracer uptake. In the context of the anatomical imaging (pre- and post-op), the most intense left-sided focus was suspected to represent physiological uptake within normal gland and the right-sided focus to represent residual somatotroph tumour. In contrast, FET-PET did not clearly identify a discrete focus of intrasellar uptake and only showed physiological uptake in the cavernous sinuses. Four months after CyberKnife therapy targeting the suspected tumour in the right cavernous sinus – and limiting the radiation dose to the physiological pituitary gland to ≤20% of the maximum – the insulin-like growth factor I declined from 1.55 to 1.18 times the upper limit of normal. No new pituitary deficits were observed.

Conclusion: This case confirms a role for MET-PET in accurate localisation of residual tumour in acromegaly and is consistent with previously published studies. Although not matching the higher resolution of MET-PET, DOTATOC-PET facilitated similar clinical decision-making. In contrast, FET-PET did not offer any diagnostic benefit in this case.