Longitudinal evaluation of the natural history of conservatively managed nonfunctioning pituitary adenomas

Context The optimal management of nonfunctioning pituitary adenomas presenting without symptomatic mass effect remains uncertain. The objective of this study was to elucidate the natural history of nonfunctioning pituitary adenomas managed conservatively. Design Volumetric evaluation of tumour growth in serial pituitary MRI scans by a single observer and retrospective review of changes in pituitary function. Patients Patients with nonfunctioning pituitary adenomas who underwent at least 2 serial pituitary MRI scans over >= 6 months between 2003 and 2013 prior to any intervention. Measurements Primary end-point was a >= 20% increase in volume or surgery. Secondary end-points were rate of pituitary dysfunction and pituitary apoplexy. Results Fifty nonfunctioning pituitary adenomas (23 macroadenomas and 27 microadenomas, mean age 49, range 17-85 years) were identified. Mean follow-up was 36 months (range 6-79). An increase in volume occurred in macroadenomas (P < 0.01) but not in microadenomas (P = 0.44). A >= 20% increase in volume occurred in nine of 23 macroadenomas compared with two of 27 microadenomas (P < 0.05). Five macroadenomas (one with new visual field defect) and one microadenoma proceeded to surgery (P = 0.08). Hormone deficiency was present in four of 24 macroadenomas vs 0 of 27 microadenomas (P < 0.05) at baseline, while new hormone deficiency developed in only two macroadenomas during follow-up. Pituitary apoplexy occurred in one microadenoma. A growth rate of >10 mm(3)/month assessed at approximately 2 years of follow-up among the macroadenoma group was highly predictive (sensitivity and specificity of 90%) of a >= 20% increase in volume or surgery. Conclusions Nonfunctioning pituitary macroadenomas have a greater tendency to grow and require surgical intervention while microadenomas rarely progress.