Context: Because surgical and medical therapies of acromegaly all have specific limitations, radiotherapy has been used as an adjunctive strategy. Stereotactic radiosurgery has not yet been widely evaluated.

Objective: The objective was to perform an analysis of long-term hormonal effects and tolerance of gamma knife radiosurgery.

Design: Eighty-two patients were prospectively studied over a decade, with a mean follow-up of 49.5 months.

Setting: All patients were treated at the Department of Functional Neurosurgery of Marseille, France.

Patients: The patients included 82 with active acromegaly, of whom 63 had previous transsphenoidal surgery.

Intervention: Intervention included radiosurgery using the Leksell Gamma Unit B model.

Main Outcome Measures: Remission was diagnosed when mean GH levels were less than 2 ng/ml and IGF-I was normal for age off somatostatin agonists (at least 3 months).

Results: Seventeen percent of the patients were in remission without any treatment. Twenty-three percent previously uncontrolled on somatostatin agonists fulfilled the same criteria after gamma knife while maintained on medical treatment. Initial GH and IGF-I levels off somatostatin agonists were significantly higher in uncured than in remission group (P = 0.01 and 0.047, respectively). Withdrawal of somatostatin agonists at the time of radiosurgery had no incidence on the outcome. No significant difference was found in success rate whether patients had previously been treated or not. Long-term side effects included complete (n = 2) or partial (n = 12) hypopituitarism diagnosed 1–7 yr after gamma knife.

Conclusions: Gamma knife radiosurgery may represent a therapeutic approach in patients with moderate initial or residual GH hypersecretion.