BACKGROUND AND OBJECTIVES: There is conflicting evidence on the significance of adrenocorticotrophic hormone (ACTH) staining in the prognosis of nonfunctioning pituitary neuroendocrine tumors (NFpitNETs). The objective of this study was to define the effect of ACTH immunostaining on clinical and radiographic outcomes of stereotactic radiosurgery (SRS) for NFpitNETs. METHODS: This retrospective, multicenter study included patients managed with SRS for NFpitNET residuals. The patients were divided into 2 cohorts: (1) silent corticotroph (SC) for NFpitNETs with positive ACTH immunostaining and (2) non-SC NFpitNETs. Rates of local tumor control and the incidence of post-treatment pituitary and neurological dysfunction were documented. Factors associated with radiological and clinical outcomes were also analyzed. RESULTS: The cohort included 535 patients from 14 centers with 84 (15.7%) patients harboring silent corticotroph NFpitNETs (SCs). At last follow-up, local tumor progression occurred in 11.9% of patients in the SC compared with 8.1% of patients in the non-SC cohort (P = .27). No statistically significant difference was noted in new-onset hypopituitarism rates (10.7% vs 15.4%, P = .25) or visual deficits (3.6% vs 1.1%, P = .088) between the 2 cohorts at last follow-up. When controlling for residual tumor volume, maximum dose, and patient age and sex, positive ACTH immunostaining did not have a significant correlation with local tumor progression (hazard ratio = 1.69, 95% CI = 0.8-3.61, P = .17). CONCLUSION: In contemporary radiosurgical practice with a single fraction dose of 8-25 Gy (median 15 Gy), ACTH immunostaining in NFpitNETs did not appear to confer a significantly reduced rate of local tumor control after SRS.

Department of Endocrinology and Metabolism University of Virginia Health System Charlottesville Virginia USA

Department of Neurological Surgery University of Pittsburgh Pittsburgh Pennsylvania USA

Department of Neurological Surgery University of Virginia Health System Charlottesville Virginia USA

Department of Neurosurgery and Radiotherapy Postgraduate Institute of Medical Education and Research Chandigarh India

Department of Neurosurgery Keck School of Medicine of USC Los Angeles California USA

Department of Neurosurgery Koc University School of Medicine Istanbul Turkey

Department of Neurosurgery Neurological Institute Taipei Veteran General Hospital Taipei Taiwan

Department of Neurosurgery NYU Langone New York New York USA

Department of Radiation and Stereotactic Neurosurgery Na Homolce Hospital Prague Czech Republic

Department of Radiology Dominican Gamma Knife Center and CEDIMAT Santo Domingo Dominican Republic

Division of Neurosurgery Université de Sherbrooke Centre de recherché du CHUS Sherbrooke Québec Canada

Division of Radiation Oncology Department of Oncology University of Alberta Edmonton Alberta Canada

Gamma Knife Center Mayfield Clinic Cincinnati Ohio USA

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