Prospective Observational Study of 118 Clinically Nonfunctioning Pituitary Adenomas

A clinically nonfunctioning pituitary adenoma (CNFPA) is the likely diagnosis in patients presenting with a sellar mass consistent with an adenoma on imaging and without clinical or laboratory evidence of hormone excess. A better understanding of the outcome of observation alone for CNFPAs not requiring surgery at diagnosis is needed.

We conducted a prospective, observational study of apparent CNFPAs ≥6 mm in diameter following the Endocrine Society guidelines for clinical, endocrine, and imaging follow-ups.

A total of 118 patients aged 56 years (range: 24.7-81)-of which 62% were female, and 72% had macroadenomas-were followed for a median of 3.9 years (range: 0.42-16). On follow-up, 49% of tumors increased in size (56% of macroadenomas and 31% of microadenomas), 12% decreased, and 39% remained unchanged. The median time to increase in size was 2.2 years (range: 0.43-12.8) for macroadenomas and 3.44 years (range: 0.41-7.4) for microadenomas (P = .16). Twenty-nine (24.6%) patients (26 who had macroadenomas and 3 who had microadenomas at diagnosis) underwent pituitary surgery after 2.58 years of follow-up (range: 0.4-7.6). Multivariable analysis found male sex to be a significant predictor of tumor growth, and macroadenoma to be a significant predictor of surgery. Most surgically removed CNFPAs were typical, hormone-immunonegative, or gonadotropin-staining tumors.

In this prospective study of 6 to 9 mm micro-CNFPAs and macro-CNFPAs followed conservatively, growth and surgery can occur within the first year or after many years of observation. Risks of enlargement and surgery are increased for certain patient groups. These factors should be considered in designing a plan for follow-up.