Gamma Knife Radiosurgery for Brain Metastasis from Primary Thyroid Cancer.

AIM: To analyze the efficacy and safety of Gamma Knife radiosurgery (GKRS) in the management of thyroid cancer brain metastases (TCBM). MATERIAL and METHODS: This retrospective study analyzed patients who underwent GKRS for TCBM at two centers between September 2005 and February 2025. Patients' clinical and radiological outcomes, including local tumor control and overall follow-up, were investigated. RESULTS: Among the 3,834 patients who underwent GKRS for brain metastases at two centers, only 0.26% had primary thyroid cancer. A total of 10 patients with 40 TCBM were treated by GKRS, with a median of two metastases per patient. The most common metastasis site was the frontal lobe (47.5%), and 60% of patients had multiple metastases. Papillary carcinoma was the most frequent histological subtype (57.1%). The median latency from thyroid cancer diagnosis to the development of brain metastases was 22 months. The median GKRS dose was 23 Gy, and local failure occurred in 5% of treated metastases. Radiation-induced necrosis was observed in one case and resolved without clinical impact. Intracranial distant metastases developed in two patients. The median follow-up was 8 months, and 80% of patients died during follow-up, with one death attributed to brain metastasis. CONCLUSION: The limited number of patients and the short follow-up period, partly reflecting the aggressive nature of TCBM, may have influenced the study results. Nevertheless, despite the short follow-up, GKRS provided favorable local control without significant adverse effects, suggesting that it may be an effective treatment option for TCBM.