Stereotactic Radiosurgery for Acromegaly

Context: The role of stereotactic radiosurgery (SRS) in acromegaly is being assessed. Objective: We evaluated the efficacy and safety of SRS for patients with acromegaly. Prognostic factors related to outcomes were also analyzed. Design: This was a retrospective study of patients treated with SRS at the University of Virginia; the data were collected from 1989 to 2012, with a median follow-up of 61.5 months. Patients: A total of 136 patients underwent SRS for acromegaly. Diagnosis of acromegaly was based on the combination of clinical features and biochemical assessment, including the serum GH level and age-and gender-matched serum IGF-1 level. All patients underwent a complete endocrine evaluation, neuroimaging study, and ophthalmic examinations before SRS. Main Outcome Measures: After withdrawal of GH- or IGF-1-altering medications, patients who had an oral glucose tolerance test GH of < 1.0 ng/mL or normal IGF-1 were considered in remission. Post-radiosurgical hypopituitarism was defined as a decrease in one or more hormones below normal. Results: With a median follow-up of 61.5 months, 65.4% of the patients achieved remission. The mean time to remission was 27.5 months. The actuarial remission rates at 2, 4, 6, and 8 years after radiosurgery were 31.7, 64.5, 73.4, and 82.6%, respectively. Favorable prognostic factors for remission included a higher margin radiation dose, higher maximum dose, and lower initial IGF-1 level. New pituitary hormone deficiency occurred in 43 patients (31.6%); two patients (1.5%) developed panhypopituitarism. Corresponding risk factors for new pituitary hormone deficiency were a margin dose >25 Gy and tumor volume >2.5 mL. Other complications included an adverse radiation effect in one patient, visual deterioration in four, and new oculomotor nerve palsy in one. Conclusion: SRS affords a reasonable rate of endocrine remission in patients with acromegaly and generally does so with a low rate of adverse effects.