Gamma Knife Radiosurgery for Patients With Nonfunctioning Pituitary Adenomas: Results From a 15-Year Experience

Purpose To evaluate the efficacy and complications of stereotactic radiosurgery for patients with nonfunctioning pituitary adenomas (NFA). Methods and Materials This was a retrospective review of 62 patients with NFA undergoing radiosurgery between 1992 and 2004, of whom 59 (95%) underwent prior tumor resection. The median treatment volume was 4.0 cm3 (range, 0.8–12.9). The median treatment dose to the tumor margin was 16 Gy (range, 11–20). The median maximum point dose to the optic apparatus was 9.5 Gy (range, 5.0–12.6). The median follow-up period after radiosurgery was 64 months (range, 23–161). Results Tumor size decreased for 37 patients (60%) and remained unchanged for 23 patients (37%). Two patients (3%) had tumor growth outside the prescribed treatment volume and required additional treatment (fractionated radiation therapy, n = 1; repeat radiosurgery, n = 1). Tumor growth control was 95% at 3 and 7 years after radiosurgery. Eleven (27%) of 41 patients with normal ( n = 30) or partial ( n = 11) anterior pituitary function before radiosurgery developed new deficits at a median of 24 months after radiosurgery. The risk of developing new anterior pituitary deficits at 5 years was 32%. The 5-year risk of developing new anterior pituitary deficits was 18% for patients with a tumor volume of ≤4.0 cm3 compared with 58% for patients with a tumor volume >4.0 cm3 (risk ratio = 4.5; 95% confidence interval = 1.3–14.9, p = 0.02). No patient had a decline in visual function. Conclusions Stereotactic radiosurgery is effective in the management of patients with residual or recurrent NFA, although longer follow-up is needed to evaluate long-term outcomes. The primary complication is hypopituitarism, and the risk of developing new anterior pituitary deficits correlates with the size of the irradiated tumor.