Hypopituitarism after Gamma Knife surgery for postoperative nonfunctioning pituitary adenoma

Area of Science:

• Neurosurgery
• Endocrinology
• Radiation Oncology

Background:

• Nonfunctioning pituitary adenomas (NFPA) are common intracranial tumors.
• Transsphenoidal surgery (TSS) is a primary treatment for NFPA.
• Gamma Knife surgery (GKS) is used for residual or recurrent NFPA after TSS.

Purpose of the Study:

• To identify clinical parameters predicting hypopituitarism after GKS in NFPA patients treated with prior TSS.
• To analyze long-term follow-up data from combined pituitary function tests (CPFT).

Main Methods:

• Retrospective analysis of 76 NFPA patients who underwent TSS followed by GKS (2001-2015).
• Evaluation of pre- and post-GKS CPFT, tumor characteristics, radiation dosimetry, and clinical outcomes.
• Statistical analysis to determine predictive factors for hypopituitarism.

Main Results:

• Hypopituitarism developed in 24.5% of patients post-GKS.
• Patients with normal pre-GKS hormonal states had a significantly higher incidence of post-GKS hypopituitarism (41.7% vs. 10.3%).
• Predictive factors included tumor volume, distance to pituitary stalk, and radiation dose to the pituitary stalk and normal gland.

Conclusions:

• Radiation dose to the pituitary stalk and normal gland are critical for preventing post-GKS hypopituitarism.
• Proposed cutoff values for radiation doses can aid in minimizing hypopituitarism risk.
• Pre-GKS hormonal status is an important consideration in risk assessment.