Gamma knife stereotactic radiosurgery for acromegaly

Abstract

Gamma knife radiosurgery (GKR) is an adjuvant treatment for acromegaly if surgery fails to normalize GH hypersecretion. To examine the effect of GKR on tumor growth and hypersecretion, and to characterize the adverse effect of this treatment. Cross-sectional follow-up study. First, retrospective data pre- and post-GKR were collected. PATIENTS then underwent a predefined survey including radiological, endocrinological, ophthalmological, and neurosurgical evaluation. Norwegian National Center for gamma knife treatment. Sixty-one patients treated with GKR for acromegaly. Out of 55, 53 living patients underwent a detailed survey. The mean follow-up was 5.5 years. No patient was lost to follow-up. Tumor growth was stopped in all patients. At 3, 5, and 10 years after GKR, 45, 58, and 86% of patients had normal IGF-I levels. Consecutive hormone value analysis showed that patients receiving GH-suppressive medication had a more rapid decline in hypersecretion than those who did not receive such medication. Evaluated by survey baseline values alone, non-elevated IGF-I and GH levels below 5 mIU/l were found in 38%. GH-suppressive medication was terminated in 16 out of 40 patients following GKR. Nine out of 53 surveyed patients (17%) had normal IGF-I and GH nadir below 2.6 mIU/l at glucose tolerance tests, while not on hormone-suppressive medication. Two patients developed minor visual field defects. Eight patients started hormone substitution therapy during the follow-up period. GKR is an effective adjuvant treatment for residual acromegaly, carrying few side effects.