Non-functioning pituitary adenomas may present without any symptomatic mass effect and minimal hormonal dysfunction. The majority of these lesions are managed conservatively with serial neuroimaging to detect those that might show significant expansion and therefore require surgery. Data on the optimal follow-up of these tumours are sparse.
Non-functioning pituitary adenomas with serial MRIs over at least 6 months between 2003 and 2013 were identified. Patients with apoplexy, visual field defect, previous sellar surgery or radiation were excluded. Longitudinal data were collected for hormonal function and pituitary tumour volume, with measurements undertaken by a single viewer (NL).
53 non-functioning pituitary adenomas (24 macroadenomas and 29 microadenomas) were identified where the initial plan was for observation. Mean follow up was 35.2 months (range 6-73), and age was 49 years (range 17-85). Those with macroadenomas were older – 59.1 ± 3.9 vs 40.8 ± 2.7 years, P< 0.001. Overall, there was a significant increase in tumour volume over the follow up period (P=0.026), with the mean percent increase in size being 9.9 ± 5.5%. A significant increase in size occurred in macroadenomas (1647 ± 221 to 1984 ± 336 mm3, P = 0.026) but not microadenomas (169 ± 25 to 178 ± 35 mm3, P=0.75). A >20% increase in size occurred in 6/24 macros compared with 2/29 micros, but this failed to reach significance. Hormonal dysfunction was present in 11/53 (21%) at baseline. New hormone axis deficiency developed in only 2 macroadenoma patients during follow-up. Seven patients (all macroadenomas) proceeded to surgery after a mean of 3.1 years (range 1-6).
Non-functioning pituitary macroadenomas have a greater tendency to grow and require surgical intervention than microadenomas. Microadenomas rarely progress and could be safely reimaged at an interval of 3 years for the first follow-up scan.