Growth Pattern and Prognostic Factors of Untreated Nonfunctioning Pituitary Adenomas

OBJECTIVE: Pituitary adenomas (PAs) are often detected as incidental findings. However, the natural history remains unclear. The objective of this study was to evaluate the natural history and growth pattern of untreated PAs. METHODS: Between 2003 and 2014, 59 PAs were managed with clinico-radiological follow up for longer than 12 months without any kind of therapeutic intervention. Tumor volumes were calculated at initial and last follow-up visit, and tumor growth during the observation period was determined. Data were analyzed according to clinical and imaging characteristics. RESULTS: The mean initial and last tumor volume and diameter were 1.83±2.97 mL and 13.77±6.45 mm, 2.85±4.47 mL and 15.75±8.08 mm, respectively. The mean annual tumor growth rate was 0.33±0.68 mL/year during a mean observation period of 46.8±32.1 months. Sixteen (27%) PAs showed tumor growth. The initial tumor size (HR, 1.140; 95% confidence interval, 1.003–1.295; p=0.045) was the independent predictive factor that determined the tumor growth. Six patients (11%) of 56 conservatively managed non-symptomatic PAs underwent resection for aggravating visual symptoms with mean interval of 34.5 months from diagnosis. By Cox regression analysis, PAs of last longest diameter over 21.75 mm were a significant prognostic factor for eventual treatment. CONCLUSION: The initial tumor size of PAs was independently associated with the tumor growth. Six patients (11%) of conservatively managed PAs were likely to be treated eventually. PAs of last follow-up longest diameter over 21.75 mm were a significant prognostic factor for treatment. Further studies with a large series are required to determine treatment strategy.