Giant GH-secreting pituitary adenomas: management of rare and aggressive pituitary tumors

Objectives: Patients with acromegaly usually harbor macroadenomas measuring between 10 and 30 mm in maximal diameter. Giant (adenoma size >= 40 mm) GH-secreting pituitary tumors are rarely encountered and the aim of this study is to analyze different methods for managing them. Design and methods: We have identified 34 patients (15 men and 19 females) with giant adenomas among 762 subjects (4.5%) with acromegaly in our records, and characterized their clinical characteristics and response to treatment. Results: Mean age at diagnosis was 34.9 +/- 12.5 years (range, 16-67 years). Mean adenoma size was 49.4 +/- 9.4 mm (range, 40-80 mm); 30 adenomas showed cavernous sinus invasion and 32 had suprasellar extension. Twenty-nine (85%) patients had visual field defects. Mean baseline IGF1 was 3.4 +/- 1.8XULN. All patients except one underwent pituitary surgery (one to three procedures), but none achieved hormonal remission following first surgery. Among the 28 subjects with visual disturbances, 14 recovered post-operatively and 13 improved. Treatment with somatostatin analogs was given to all patients after surgical failure. Six achieved remission, nine others were partially controlled (IGF1<1.5XULN; 3/9 when combined with cabergoline), and 17 did not respond (two were lost). Nine patients were treated with pegvisomant, alone (n=4) or in combination with somatostatin analogs (n=5); five are in remission and two are partially controlled. Pasireotide-LAR achieved hormonal remission in one of the six patients. Currently, after a mean follow-up period of 8.9 years, 17 patients are in biochemical remission, eight are partially controlled, and seven are uncontrolled (two were lost to follow-up). Conclusions: Giant GH-secreting adenomas are invasive, uncontrolled by surgery, and respond poorly to medical treatment. Aggressive multimodal therapy is critical for their management, enhancing control rate and biochemical remission.