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±1.8×ULN. 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<1.5×ULN; 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.