Endocrine Abstracts

Background: Transsphenoidal adenomectomy of GH-secreting pituitary tumour is a first-line treatment of acromegaly. Pharmacological treatment is recommended if surgery did not lead to disease remission. Pathological assessment of postoperative tissue provides clinicians with valuable information on the disease course.

Aim: The aim of this study was to assess whether clinical, imaging, and pathological characteristics can predict surgical remission and response to first-generation somatostatin analogs (SRLs) and pasireotide LAR in acromegaly patients.

Patients and methods: A retrospective analysis of a study cohort of 120 patients with acromegaly, treated in one endocrinology centre was performed. Data on demographics, hormonal and imaging results, pathological evaluation (immunostaining for pituitary hormones, Ki-67 index and granulation pattern) and treatment outcome was extracted from the Polish Acromegaly Registry and analyzed.

Results: Patients who achieved surgical remission were older at diagnosis (50 vs. 37 years on average, P<0.001), had lower fasting GH, IGF-1 and PRL concentrations at diagnosis (4.68 vs. 18.9µg/l on average, P<0.001; 2.99 vs. 3.53xULN on average, P=0.004, 11.1 vs. 22.4 ng/ml on average, P=0.015, respectively) and had smaller tumours (12 vs. 24 mm on average, P<0.001) which were less invasive than in patients with active acromegaly after surgery. The pathology results showed that patients with surgical remission more often had densely granulated tumours (73.17% vs. 40.00%, P=0.001) with positive staining for α-subunit (58.33% vs. 35.48%, P=0.021) and lower Ki-67 index (87.50% vs. 65.57% with Ki-67 index<1%, P=0.002) compared to patients without surgical remission. Patients, who responded well to first-generation SRLs, presented less common extrasellar expansion and compression of the optic chiasm at diagnosis of acromegaly (58.62% vs. 90.00%, P=0.006 and 13.79% vs. 56.67%, P=0.001, respectively) compared to patients with poor response to SRLs. They also had more common densely granulated tumours (62.96% vs. 14.29%, P<0.001). However, no significant differences between patients with good and poor response to pasireotide LAR were found. In multivariate logistic regression analysis, independent predictors of post-surgical remission were normoprolactinaemia at diagnosis (OR=5.87, P=0.023), densely granulated tumour in electron microscopy (OR=5.92, P=0.012) and lower fasting GH concentration at diagnosis (OR=0.88, P=0.001).

Conclusions: Patients with densely granulated somatotroph tumours are more likely to achieve surgical remission and to respond well to first-generation SRLs. Positive staining for α-subunit and lower Ki-67 index increase the likelihood of surgical remission in acromegaly. The pathological assessment of tumour tissue is an important part of acromegaly patient’s evaluation providing valuable information on tumour’s characteristics. Together with clinical and imaging parameters it can help to predict the treatment outcome.