Endocrine Abstracts

JOINT1241

Introduction: Pituitary surgery is the first-line treatment for acromegaly in most cases. While clinical and radiological predictors of remission have been extensively evaluated, few studies have analysed pathological prognostic factors, and evidence regarding histotype remains conflicting. Acromegaly histotypes mainly include pure GH adenomas, which can be either densely (DG) or sparsely granulated (SG), as well as GH-PRL adenomas.

Objectives: The primary objective was to assess the impact of histotype on acromegaly remission, defined as normal IGF-1 levels without treatment 3 months after surgery and at last follow-up. The secondary objective was to evaluate the influence of histotype on acromegaly control at last follow-up, defined as IGF-1 ≤1.2× the upper limit of normal (ULN) with or without medical treatment.

Methods: Monocentric retrospective study including 162 patients with GH or GH-PRL adenomas who underwent endoscopic transsphenoidal surgery performed by an expert surgeon between 2012 and 2022.

Results: Among 162 patients, 63 (38.9%) had GH-PRL adenomas, while 99 (61.1%) had pure GH adenomas, including 59 DG (36.4%) and 40 SG (24.7%). Median age (48 years [IQR: 34-58]), IGF-1 (2.9×ULN [IQR: 2.1-3.7]), maximum tumour diameter (14 mm [IQR: 10-21]), and invasion rate (38%) did not significantly differ between GH and GH-PRL groups. Compared to pure GH adenomas, GH-PRL adenomas were more frequently p53-positive (P<0.01), had a higher mitotic count (P<0.05), and higher SST2 expression (P<0.01). Trouillas grade did not differ significantly between GH and GH-PRL adenomas. Compared to SG adenomas, DG adenomas had a lower Trouillas grade (P<0.05), lower SST5 expression (P<0.01), higher SST2 expression (P<0.001), and were more frequently SF1-positive (50% versus 0%, P<0.01). The 3-month remission rate was 52% for pure GH and 49% for GH-PRL adenomas, with no significant difference. At last visit, after a median follow-up of 33 months [IQR: 17-61], remission rates remained comparable between pure GH (63%) and GH-PRL adenomas (62%). The control rate at last follow-up for pure GH (89%) was not significantly different from GH-PRL adenomas (95%). Among patients requiring medical treatment, all controlled pure adenomas received monotherapy, while 35% of GH-PRL adenomas required combined therapy. In pure GH adenomas, no significant difference in remission was observed between DG and SG adenomas at 3 months or last follow-up. Similarly, control rates did not differ significantly.

Conclusion: Our results indicate that histotype is not significantly associated with remission or control of acromegaly and do not support the WHO classification, which considers SG high-risk pituitary adenomas.