Effect of stereotactic radiosurgery before bilateral adrenalectomy for Cushing's disease on the incidence of Nelson's syndrome

Object Nelson's syndrome (NS) is a significant and frequent risk for patients with Cushing's disease (CD) who undergo bilateral adrenalectomy. A recent study has shown tumor progression in 47% of patients at risk for NS. The authors sought to define the rate of NS in patients who were treated with Gamma Knife stereotactic radiosurgery (GK SRS) prior to bilateral adrenalectomy. Methods Consecutive patients with CD who were treated with GK SRS after pituitary surgery but before bilateral adrenalectomy were included. Serial MRI sequences were analyzed to evaluate for pituitary tumor growth. Clinical evaluations were performed to screen for NS. Follow-up for adrenocorticotropic hormone levels and hormone studies of other pituitary axes was performed. Results Twenty consecutive patients were followed with neuroimaging and clinically for a median of 5.4 years (range 0.6–12 years). One patient (5%) developed pituitary tumor growth consistent with NS 9 months after adrenalectomy. By Kaplan-Meier analysis, progression-free survival was 94.7% at 1, 3, and 7 years. No predisposing factors were identified for the tumor progression. Two patients developed new pituitary dysfunction and no patient developed cranial neuropathy or visual deficit after GK SRS. Conclusions These findings suggest that GK SRS not only serves a role as second-line therapy for CD, but that it also provides prophylaxis for NS when used before bilateral adrenalectomy.