LONG-TERM OCTREOTIDE THERAPY IN GROWTH HORMONE-SECRETING PITUITARY-ADENOMAS - EVALUATION WITH SERIAL MR

PURPOSE: To compare the changes in tumor volume with length of octreot ide treatment in patients with acromegaly, to analyze signal alteratio ns of the pituitary mass during treatment and to determine an optimal MR imaging protocol. METHODS: Eighteen patients with growth hormone (G H)-secreting pituitary adenomas were studied with MR imaging before an d during octreotide treatment. The length of follow-up was 9 to 70 mon ths. Tumor volume, extension, and signal characteristics were evaluate d. RESULTS: The total pituitary volume decreased in 16 patients by a m ean of 37%. In 11 patients the tumor could be demarcated from the norm al gland, and mean tumor reduction was 51%. Most of the tumor reductio n took place within the first year, but an additional effect was noted in four patients during the following 3 years. Tumor reexpansion, hem orrhage, or necrosis did not occur. Serum GH levels were effectively l owered within the first year, with slight additional reductions therea fter. CONCLUSION: In long-term octreotide treatment of GH-secreting pi tuitary adenomas, tumor shrinkage occurs primarily during the first ye ar, but effects are noted up to 4 years. The treatment may be consider ed an alternative to surgery in the select group of patients in whom t he peripheral effects of chronic GH elevation, as determined by serum insulinlike growth factor I (IGF-I), are controlled. We suggest MR ima ging with T1-weighted coronal and sagittal images at baseline and afte r 3 and 12 months, with additional MR imaging if GH or IGF-I levels ri se during treatment. At baseline, both noncontrast and contrast-enhanc ed images should be obtained. Unenhanced images may be sufficient duri ng follow-up unless tumor reexpansion occurs or surgery is anticipated .