Efficacy of whole-sellar gamma knife radiosurgery for magnetic resonance imaging-negative Cushing's disease.

Background: Corticotroph adenoma delineation in Cushing's disease (CD) patients with previous surgery can be challenging. This study investigated the outcome of whole-sellar gamma knife radiosurgery (GKRS) in MRI-negative, but hormone-active CD patients with prior failed treatment attempts.

Methods: We retrospectively analyzed data of nine CD cases who underwent whole-sellar GKRS between April 2008 and April 2020 at a single center. Remission was determined as normal morning serum cortisol, normal 24-hour urinary free cortisol (UFC) or extended postoperative requirement for hydrocortisone replacement.

Results: Median age was 35.0 years, and most of the cases were female (89%). All subjects had undergone previous surgery. The mean pre-GKRS morning serum cortisol and 24-hour UFC were 27.5 μg/dL and 408.0 μg, respectively. Target volume varied from 0.6 to 1.8 cc, and the median margin dose was 28 Gy. The median duration of endocrine follow-up was 105 months, and initial endocrine remission was achieved in eight subjects (89%) at a median time of 22 months. The actuarial initial remission was 44% at two years, 67% at four years, and 89% at six years. The mean recurrence-free survival was 128 months. Age and pre-GKRS morning serum cortisol was found to be predictors for initial and durable endocrine remissions. New-onset hypopituitarism was observed in two of five patients (40%). None of the patients developed new neurological deficits and had GKRS-related adverse events during the follow-up.

Conclusions: Whole-sellar GKRS is a safe and efficient method to manage MRI-negative CD and provides similar GKRS outcome rates as in MRI-positive CD.