MON-303 Giant Growth Hormone Secreting Pituitary Adenomas: A Single Institution Case Series

The prevalence of growth hormone (GH)-secreting pituitary adenoma is around 11-13% of all pituitary adenomas. Giant GH-secreting pituitary adenomas (≥ 4 cm) are rare tumors, and its prevalence of among acromegalic patients is <5%. This is a retrospective cohort study including patients with giant GH-secreting pituitary adenomas. The study population consisted of 10 patients (5 M/5 F). The mean age at diagnosis was 33.0±12.9 yrs (11-55 yrs). The mean delay between first symptom onset and diagnosis was 2.9 years. The most frequent symptoms were acral enlargement and facial changes (80%), followed by headache (70%) and visual deterioration (50%). One patient had epilepsy. Amenorrhea was presented in three females but obvious galactorrhea in two. The mean adenoma diameter was 42.6±4.7 mm (40-51 mm) at diagnosis. The vast majority of adenomas presented suprasellar extension (100%) or cavernous sinus invasion (80%). Cystic adenomas accounted for 50%. At presentation, mean GH and IGF-1 levels were 40.0±21.4 ng/mL (14.8-51.0) and 2.62±1.09 x ULN (1.08-3.96), respectively. Six patients presented with PRL cosecretion. At diagnosis maximal tumor diameter was not correlated with GH or IGF-1 levels. All patients underwent pituitary surgery as first-line treatment. Three cases were treated with an endoscopic approach and four cases with a microscopic approach. Transcranial approach was also employed in three cases. Postoperative mean GH and IGF-1 levels were 14.9±16.1 ng/mL (0.6-51.0) and 2.25.±0.82 x ULN (1.48-3.74), respectively. After first surgery, only one patient had more than 50% reduction in IGF-1 levels. Five patients (50%) underwent repeat surgery on two to three procedures because remission was not achieved. Postoperative somatostatin receptor ligands (SRLs) were used by all patients. Six patients were treated with dopamine agonist in combination with SRL. Six patients (60%) received postoperative radiotherapy. The mean follow-up period was 12.6±5.3 yrs (4-21 yrs). The mean GH and IGF-1 levels were 1.47±1.54 ng/mL (0.08-5.25) and 0.73±0.44 x ULN (0.08-1.56), respectively at the last visit. Residual adenoma was present at the last MRI in eight patients (mean diameter 9.0±3.6 mm). Panhypopituitarism rose from 10% at baseline to 30% at the last visit. During follow-up, one patient diagnosed breast cancer, while another diagnosed thyroid papillary cancer. Giant GH-secreting pituitary adenomas can have a clinically aggressive behavior with mass effect. Moreover, treatment in patients with giant GH-secreting pituitary adenoma is complex and multimodal therapy is necessary.