Conservatively managed non-functioning pituitary macroadenomas: cohort study from the UK Non-functioning Pituitary Adenoma Consortium

Objective: Surveillance is often adopted for asymptomatic non-functioning pituitary macroadenomas (macroNFPAs). Due to low quality evidence, uncertainty remains on optimal frequency of imaging/biochemical monitoring and indications for surgery. We assessed the natural history and outcomes of patients with macroNFPA who had monitoring as initial management choice from the UK NFPA Consortium.

Design: Multicentre, retrospective, cohort study involving 21 UK endocrine departments.

Methods: Clinical, imaging, hormonal data of 949 patients followed-up between January, 1, 2005 and March, 1, 2022 were analysed.

Results: Incidence rate for tumour enlargement was 9.8 per 100 patient-years (95%CI, 8.8-10.8), with cumulative probabilities 1.6%, 8.1%, 18.4%, 29.2%, 43.6% at 6-months, 1-year, 2-year, 3-year, 5-year follow-up, respectively; rates were higher in tumours abutting/displacing optic chiasm (OC) than those not in contact with it. Amongst macroNFPAs not in contact with OC showing enlargement within six months, none impacted visual fields. In tumours with enlargement and continued monitoring (median 2.6 years), further growth occurred in 60.5% (33.8% probability at 2-years), stability in 35.5%, shrinkage in 4.0%. Rates of new pituitary hormone deficits were 4.0%-4.9%, mainly driven by tumour enlargement. After transsphenoidal surgery, rates of hypopituitarism reversal were 12%-17% and of additional anterior pituitary hormone deficits 12%-15% (permanent vasopressin deficiency 3.5%).

Conclusions: Our data provide evidence for monitoring protocols. MacroNFPAs not in contact with OC require less frequent imaging and first follow-up scan can be delayed to one year. After first enlargement, variable tumour behaviour can occur. New hypopituitarism in stable tumours is rare, challenging necessity of regular pituitary function assessment.