The aim of this study is to evaluate efficacy and safety of Gamma Knife radiosurgery (GKRS) for treatment of incompletely removed non-functioning pituitary adenoma (NFPA).

     Between 1994 and 2008, 166 patients (82 men and 84 women) with a diagnosis of NFPA who had previously undergone surgical treatment at our center underwent GKRS for residual pituitary tumor. 108 patients had undergone surgery once; 49 patients twice and the remaining 9 patients, three times. No patient had previously received external fractionated radiotherapy.

     Medial marginal dose was 15 Gy with isodose at 50%; median dose to optic chiasm was 7.4 Gy (IQR 5.1- 9.5 Gy). GKRS was performed in 111cases (67.7 %) to prevent regrowth of residual tumor, while 53 cases (32.3 %) underwent GKRS after the regrowth of residual NFPA. Baselines and follow-up studies included MRI, hormone evaluation and neuro-ophthalmologic examination 6 and 12 moths after GKRS and then at yearly intervals.

      The mean follow-up after GKRS was 43.6±2.9months. 153 patients have had at least 6 months of follow-up after radiosurgery and are included in the following analyses. Volume of treated residual tumor was 2.2±0.2 cm3 (IQR 0.2 – 17.7 cm3). Three patients had severe headache for two months after GKRS. Visual function did not deteriorated in any patients. New cases of hypogonadism, hypothyroidism and hypoadrenalism occurred in 11.4 %, 6.1 % and 3.6% of patients at risk. There were 7 recurrences (4.6%). The 3 years recurrence-free survival was 97.9% (95% CI, 95.1-100) and 5 year recurrence free survival was 94.8% (95% CI, 89.8-99.9).

     This is a retrospective study.

     GKRS was effective in controlling the growth of residual or recurring NFPA after previous maximal surgical debulking.

     Also, GKRS carries a low risk of side effects and hypopituitarism.