Stereotactic Radiosurgery for Acromegaly

Abstract

The role of stereotactic radiosurgery (SRS) in acromegaly is being assessed. We evaluated the efficacy and safety of SRS for patients with acromegaly. Prognostic factors related to outcomes were also analyzed. 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. 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. 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. 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. SRS affords a reasonable rate of endocrine remission in patients with acromegaly and generally does so with a low rate of adverse effects.