1348 Stereotactic Radiosurgery for Nonfunctioning Pituitary Tumor: A Multicenter Study of New Pituitary Hormone Deficiency

INTRODUCTION: Stereotactic radiosurgery (SRS) is used to treat residual and recurrent nonfunctioning pituitary adenomas (NFPA). Hypopituitarism is the most common complication with increasing rates over time. We present the largest multicentric cohort evaluating outcomes after radiosurgery for NFPA. METHODS: Twelve centers contributed retrospective data on 869 patients treated with SRS between 1992 and 2022. Tumor progression was defined as a volumetric increase of =20% from baseline. New-onset hypopituitarism was defined as dysfunction of at least 1 pituitary axis. Kaplan–Meier curves were plotted for the probability of tumor control and new onset hypopituitarism. Cox regression was used to assess predictive factors for tumor control and new pituitary hormone deficiency. RESULTS: A total of 869 patients (median age 52.5 years [Interquartile range (IQR):18.9]) were treated using a median margin dose of 14Gy (IQR:4) for a median tumor volume of 3.4cc (IQR:4.3). With a median radiological follow-up of 3.7 years (IQR:4.8). Volumetric tumor reduction occurred in 451 patients (51.9%), stability in 364 (41.9%) and 54 patients (6.2%) showed tumor progression. The probability of tumor control was 95.5% (95% Confidence Interval [CI]:93.8–97.3) and 88.8% (95%CI:85.2–92.5) at 5 and 10 years. A margin dose >14 Gy was associated with tumor control (Hazard Ratio [HR]:0.33, 95% CI:0.18–0.60, P<0.001). The probability of new hypopituitarism was 9.9% (95%CI:7.3–12.5) and 15.3% (95%CI:11–19.4) at 5 and 10 years. A maximum point dose >10 Gy in the pituitary stalk was associated with new pituitary hormone deficiency (HR:3.47, 95%CI:1.95–6.19). The 10-year cumulative probability of new cortisol, thyroid, gonadotroph, and growth hormone deficiency was 8%, 8.3%, 3.5%, and 4.7%, respectively. CONCLUSIONS: SRS for NFPA affords long-term tumor control (10 year:>88%) and low rates of pituitary dysfunction (10-year:15.3%).