Upfront Stereotactic Radiosurgery for Nonfunctioning Pituitary Neuroendocrine Tumors: An International, Multicenter Study

BACKGROUND AND OBJECTIVES: Upfront stereotactic radiosurgery (SRS) could be an option for nonfunctioning pituitary adenomas (NFPA) unsuitable for surgery. Only small series evaluate the results of upfront SRS; the aim of the study was to report patient outcomes from a large, international patient cohort. METHODS: The study evaluated tumor control and complications after single-session SRS in a multicentric cohort of untreated NFPA. RESULTS: In total, 132 patients (median age 51.2 [IQR: 27.1] years at SRS, median volume 2.1 [IQR: 2.9] cm 3 ) were included. The probability of tumor control was 100% (95% CI: 100-100), 98.1% (95% CI: 94.6-100), and 92.4 (95% CI: 81.6-100) at 3, 5, and 8 years after SRS. The cumulative probability of new pituitary deficit was 11.7% (95% CI: 3.8-18.9), 24.4% (95% CI: 12.1-35.1), and 29.5% (95% CI: 12.1-26.9) at 3, 5, and 8 years, respectively. No new visual field defect occurred. Before SRS, 50 patients (37.9%) presented with a visual field defect with a complete improvement in 17 (34.7%), partial improvement in 12 (24.5%), and stability in 19 (38.8%) at a last follow-up of 2.2 (3.9) years. One patient (2.0%) worsened after SRS. Before SRS, 10 patients (7.6%) presented with an oculomotor nerve palsy. One patient (0.8%) developed a new transient nerve palsy. At a last follow-up of 2.5 (4.4) years, 5 patients (45.4 35.7%) had a stability of their palsy, 1 had a partial improvement (9.1%), and 5 (45.4%) had a complete improvement. CONCLUSION: Upfront SRS represents an option for appropriately selected patients with NFPA, and it exhibits a favorable efficacy and safety profile, but a longer follow-up is required. Visual improvement is low, and careful selection of patient is required.