Aims: 11C-methionine positron emission tomography co-registered with MRI (met-PET/MRI) is a new imaging technique used for functioning pituitary adenomas. In patients with persistent acromegaly after primary therapy, met-PET/MRI can help identify the site(s) of residual pituitary adenoma when MRI appearances are inconclusive and direct further targeted intervention (Trans-sphenoidal surgery-TSS or radiotherapy).
Methods: Retrospective study of patients with acromegaly under active follow-up in a teaching hospital. Data were collected from paper and electronic records (2009 onwards). An arbitrary age cut-off of 75 was used when considering suitability for repeat TSS. Remaining patients were divided into three categories. P1: poorly controlled on somatostatin analogue (SSA) therapy and/or pegvisomant. P2: well controlled on SSA. P3: poorly controlled on dopamine agonist (DA) therapy
Results: Fifty-one patients were included, 61% female. Mean age 58.9±16.5 years. Mean age at diagnosis 43.4±16.9 years. Median follow-up of 13 years, IQR: 15.5. Twenty-three patients under the age of 75 were receiving ongoing medical treatment (P1: 10, P2:8 and P3:3). Annual cost (BNF 2017) of medical endocrine therapy for P1 category patients was £150,829 and P2 category patients was £73,466. Eight P1 category patients, willing for further intervention, have agreed to met-PET/MRI. Illustrative case: A young female patient with acromegaly on SSA+DA (P1) and diabetes mellitus on 120 units of insulin/day, both poorly controlled, underwent redo TSS influenced by met-PET/MRI (fused images). She was discharged off insulin and with intact steroid axis.
Conclusion: So far, our patients who have undergone met-PET/MRI have shown identifiable residual functioning pituitary adenoma. It has influenced our decision to put these patients forward for TSS. There are potential cost savings involved if they are able to come off medical therapies or even decrease frequency of these injections.
Acknowledgement: Cambridge team for assistance setting up met-PET/MRI. Eur J Endocrinol. 2016 Nov; 175(5):485-498.