Background: Transsphenoidal surgery (TSS) is the primary treatment of choice in acromegaly. It is important to identify patients in whom surgical cure is not attainable at an early stage, both to inform patients on expected treatment outcome and to select those who are more likely to benefit from additional therapy.

Objective: To determine the importance of several biomarkers for predicting remission after transsphenoidal surgery for acromegaly.

Methods: This single centre retrospective study included 122 acromegaly patients in whom TSS was performed as primary therapy between January 2000 and July 2019. All available preoperative MRI’s were reclassified according to the modified Knosp classification by an experienced neuroradiologist. In addition, assessment of T2-weighted signal, tumour diameters (mm) and tumour volume (cm3) was performed. Multivariate logistic regression was performed to determine the best predictors for remission according to the 2010 consensus criteria at 3 months to a year after TSS and for long-term surgical cure, defined as normalization of IGF-1 without application of postoperative treatment.

Results: Total follow-up was 10.2 (4.7;14.3) years from TSS. Absence of cavernous sinus invasion (OR: 16.914 [1.870;153.008], p= 0.012) and lower IGF-1 at diagnosis (OR: 0.976 [0.955; 0.997], p=0.025) were associated with remission at 3 months to a year after TSS. Absence of cavernous sinus invasion (OR: 21.267 2.373; 190.631], p=0.006) and lower random GH at diagnosis (OR: 0.976 [0.956; 0.995], p=0.016) were associated with long-term surgical cure.

Conclusion: Absence of cavernous sinus invasion is the most important biomarker to predict remission after TSS in acromegaly.