Endocrine Abstracts (2001) 2 OC23

Pituitary Tumour Shrinkage During Treatment of Acromegaly with Sandostatin LAR

PJ Jenkins, P Yeo, GM Besser, J Evanson & JP Monson

Depts of Endocrinology1and Radiology2, St Bartholomew's Hospital, London EC1A 7BE

Transsphenoidal surgery results in biochemical cure of approximately 50% of all acromegalic patients, depending on tumour size and surgical expertise. It is uncertain whether prior treatment with somatostatin analogues would result in tumour shrinkage and therefore improve the efficacy of subsequent surgery. Aims: To determine whether 6 months de novo treatment with Sandostatin LAR results in tumour shrinkage. Methods: 6 patients (mean age 53 yr; range 42-76) with newly diagnosed acromegaly received 4-wekly i.m. injections of Sandostatin LAR (20-30 mg) for 6 months. Tumour volume was calculated from MRI (4 patients) or CT scans performed at baseline and 3 and 6 months after initiation of treatment. 4 patients had a macroadenoma; for the two patients with a microadenoma, the whole gland volume was calculated. Results: Serum GH (mean of a day curve) decreased in all patients from 29.6±19.2 mU/l (mean±SD) to 12.1±10.5 at 3 months and 10.4±9.3 at 6 months. 3 patients achieved a level of <5 mU/l. Serum IGF-I decreased by a mean of 67% with 1 patient achieving a level within the age-matched normal range. Tumour volume decreased in all patients: baseline mean volume (range): 2429 mm3 (660-6998) to 1696 mm3 (360-4522) at 3 months and 1525 mm3 (280-4104) at 6 months. The mean % decrease (range) was 73% (54-85) at 3 months and 60% (21-97) at 6 months. The greatest shrinkage occurred in the patients with macroadenomas. There was no statistical correlation between GH response and tumour shrinkage. Conclusions: Sandostatin LAR results in shrinkage of GH secreting pituitary adenomas and its preoperative use may improve the efficacy of subsequent surgery, especially in patients with macroadenomas.

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