Proton Stereotactic Radiotherapy for Treatment of Nelson's Syndrome

Abstract

Nelson's syndrome is a rare disorder that may arise as a complication of treating Cushing's disease through bilateral adrenalectomy. It is characterized by growth of remaining pituitary adenoma and elevation of adrenocorticotropic hormone (ACTH) levels. Prior studies have established radiation therapy (RT) as a method of treating Nelson's syndrome. In this study, we evaluated the efficacy of proton stereotactic radiosurgery (PSRS) on decreasing ACTH levels and achieving disease remission in patients with Nelson's syndrome treated with SRS.A retrospective analysis of eight patients with Nelson's syndrome who received PSRS between 2007 and 2017 at our institution was conducted. All patients previously underwent bilateral adrenalectomy for treatment of Cushing's disease. Patients received PSRS at a total dose of 15 or 20 Gy(RBE) delivered in one fraction. The median clinical target volume was 5.7 cc (range 3.7-9.0 cc). ACTH levels, disease status, and post-treatment complications were followed post-SRS to assess for endocrine remission.The median follow-up was 80 months (range 35-126 months) from the end of SRS treatment. The median ACTH level decreased from 761.5 pg/mL pre-SRS to 38 pg/mL post-SRS at time of latest follow-up. Endocrine remission was achieved among six patients (75%) at a median time of 47 months (range 12 -126 months) from SRS. Three patients (38%) developed pituitary deficits (two with TSH and gonadal deficiency and one with pan-pituitary deficiency) post-SRS.SRS can be an effective treatment to achieve endocrine remission in patients with Nelson's syndrome. SRS can lead to pituitary deficits in some patients and longer follow-up is warranted to assess long-term disease control and treatment toxicity.D.W. Kim: None. G. Lee: None. E. Cai: None. B. Swearingen: None. P.H. Chapman: None. M.R. Bussiere: Consultant; American College of Radiology. A. Klibanski: None. J.S. Loeffler: None. H.A. Shih: Employee; Dartmouth Hitchcock. Research Grant; AbbVie, NIH. Honoraria; UpToDate. Consultant; Cleveland Clinic. Speaker's Bureau; prIME Oncology. advisory; The Radiosurgery Society. director of clinical operations; Massachusetts General Hospital. clinical operational leader; Massachusetts General Hospital.