Endocrine Abstracts

Patients with histology confirmed acromegaly who have undergone trans-sphenoidal surgery and radiotherapy often have active acromegaly despite no evidence of adenoma on MRI. Currently 111In Octreotide, a radioactive tracer, is used in the assessment of neuroendocrine tumours, with 70-90 percent sensitivity for detection. Studies to date however have not looked at 111In Octreotide as an alternative measure to assess patients who present with biochemically active acromegaly despite no evidence of residual tumour on MRI scanning. Furthermore, while MRI data suggests the anatomical location of the tumour, the use of 111In Octreotide may define more accurately the site of the functional tumour mass. Therefore for this study 18 patients (Age: 52.67plus/minus SD14.26) with refractory acromegaly despite trans-sphenodial surgery (2-24yr previous) and radiotherapy (pituitary fossa: 1-21yr previous) were scanned by MRI and given 111In Octreotide tracer following a 2 month treatment withdrawal. For these patients biochemical activity of the disease was defined by a 2-hour Glucose Tolerance Test with concurrent failure to suppress growth hormone(GH) levels to less than 0.5 milliunits per litre (GH patient range: 1.6-60 millunits per litre). Both the MRI and 111In Octreotide studies revealed comparable findings in all 18 patients, with no evidence of residual tumour identified (p=N.S) in 17 of them and one patient with residual tumour in the fossa which was imaged by both techniques. In summary, the findings are that in all the cases of acromegaly studied MRI and Octreotide scans correlate.

In conclusion, while Octreotide may give insight into the functionality of inoperable tumours the results it provides offer no advantages over MRI scanning which also has the ability to define the anatomy of the region. Therefore there seems to be no gain to be made in the routine post-operative scanning of this patient population with both MRI and Octreotide.