• Sven M Carlsen, Johan Svartberg, Thomas Schreiner, Sylvi Aanderud, Oivind Johannesen, Svein Skeie, Morten Lund-Johansen, Stine L Fougner, Jens Bollerslev, and POTA study group.
• Unit of Applied Clinical Research, Department of Cancer Research and Molecular Medicine, Norwegian University for Science and Technology, Trondheim, Norway. sven.carlsen@ntnu.no
• Clin. Endocrinol. (Oxf). 2011 Jun 1; 74 (6): 736-43.

ObjectiveTreatment with somatostatin analogues is the primary medical treatment of acromegaly. Controversies still exist whether acute octreotide effect predicts long-term biochemical effects, tumour regression or surgical cure. This prospective study investigates effect of 6-month treatment with octreotide long-acting repeatable (LAR) on insulin-like growth factor-1 (IGF-1) and growth hormone (GH) levels, pituitary function, tumour regression and postoperative cure in de novo acromegalic patients.Design And MethodsAfter a baseline evaluation including fasting hormone levels, MRI scan and an acute 50 μg octreotide test, 32 patients were treated with octreotide LAR 20 mg every 28th day for 6 months before surgery. Treatment effects on IGF-1 and GH levels, serum hormone levels and tumour volume were monitored. Surgical cure was evaluated 3 months postoperatively.ResultsMean tumour volume reduction was 35%, in one-third of the patients more than 50%, while approximately one-third achieved biochemical remission evaluated by normalized IGF-1 levels. The GH reduction following an acute octreotide test was 81 ± 19% and associated with long-term GH reduction (r = 0·78, P < 0·0005). However, neither acute (r = 0·29, P = 0·12) nor the long-term octreotide effect (r = 0·11, P = 0·58) on GH levels was associated with tumour volume reduction and did not predict subsequent surgical cure.ConclusionSix months of long-acting octreotide using a fixed dose, 1/3 of the patients came in biochemical remission, while 2/3 had significant tumour reduction. Moreover, an acute effect of octreotide seemed to be a prerequisite for long-term effect.© 2011 Blackwell Publishing Ltd.

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