Treatment Outcome of Gamma Knife Radiosurgery for Brain Metastasis from Thyroid Cancer: Favorable Local Control but Poor Survival

Background: Brain metastasis from thyroid cancer (TCBM) is extremely rare; thus, despite a good treatment outcome for thyroid cancer, TCBM has shown poor clinical outcomes. Considering the short survival and poor general condition of patients with TCBM, stereotactic radiosurgery may be preferred to achieve local control. Methods: A total of 25 patients with TCBM who underwent Gamma Knife radiosurgery (GKS) were initially included in this study; however, 3 patients were excluded because of a lack of data. Results: There were 7 men (31.8%) and 15 women (68.2%) and the mean age was 63.7 years. The most common type of thyroid cancer histology was papillary carcinoma. Fourteen patients (63.6%) harbored single brain metastatic tumor and 8 (36.3%) had multiple brain metastatic tumors. The mean duration from thyroid cancer diagnosis to detection of brain metastasis was 7.7 years (range, 0–23 years). The median dose of radiation of GKS was 22 Gy (range, 18–25 Gy). There was no radiation-induced complication after GKS. The median overall survival (OS) was 15 months and the 1-year OS of patients with TCBM was 63%, the 2-year OS was 38%, and the 5-year OS was 28%. The 6-month progression-free survival (PFS) for local recurrence of TCBM was 90.4%, the 1-year PFS was 84%, and the 3-year PFS was 84%. Conclusions: GKS showed favorable local control for TCBM. However, the rate of distant brain metastasis was high and median survival of patients with TCBM was only 15 months.