Developing an optimal follow-up strategy based on the natural history of nonfunctioning pituitary adenomas.

OBJECTIVE: The natural history and proper algorithm for follow-up testing of nonfunctioning pituitary adenomas (PAs) are not well known, despite their relatively high prevalence. The aim of this study was to suggest the optimal follow-up algorithm for nonfunctioning PAs based on their natural history.

METHODS: The authors followed up 197 patients with nonfunctioning PAs that had not been treated (including surgery and radiation therapy) at the time of detection, in a single center, between March 2000 and February 2017. They conducted a hormone test, visual field test, and MRI at the time of diagnosis and yearly thereafter.

RESULTS: The overall median follow-up duration was 37 months. Microadenomas (n = 38) did not cause visual disturbance, pituitary apoplexy, or endocrine dysfunction. The incidence of patients with tumor volume growth ≥ 20% was higher for macroadenomas than microadenomas (13.8 vs 5.0 per 100 person-years [PYs], p = 0.002). The median time to any tumor growth was 4.8 years (95% CI 3.4-4.8 years) for microadenomas and 4 years (95% CI 3.3-4.2 years) for macroadenomas. The overall incidence of worsening visual function was 0.69 per 100 PYs. Patients with a tumor volume growth rate ≥ 0.88 cm3/year (n = 20) had a higher incidence of worsening visual function (4.69 vs 0.30 per 100 PYs, p < 0.001). The tumor growth rate of all microadenomas was < 0.88 cm3/year. The median time to tumor growth ≥ 20% was 3.3 years (95% CI 1.8-3.9 years) in patients with a tumor growth rate ≥ 0.88 cm3/year and 4.9 years (95% CI 4.6-7.2 years) in patients with a tumor growth rate < 0.88 cm3/year.

CONCLUSIONS: The authors have devised a follow-up strategy based on the tumor volume growth rate as well as initial tumor volume. In patients with microadenomas, the next MRI study can be performed at 3 years. In patients with macroadenomas, the second MRI study should be performed between 6 months and 1 year to assess the tumor growth rate. In patients with a tumor growth rate ≥ 0.88 cm3/year, the MRI study should be performed within 2 years. In patients with a tumor growth rate < 0.88 cm3/year, the MRI study can be delayed until 4 years.