Fractionated stereotactic radiotherapy for metastatic brain tumors that recurred after gamma knife radiosurgery results in acceptable toxicity and favorable local control

Akifumi Miyakawa, Yuta Shibamoto, Shinya Takemoto, Toru Serizawa, Shinya Otsuka, Tatsuo Hirai

To treat local recurrence of brain metastases after gamma knife radiosurgery (GKS), we have used fractionated stereotactic radiotherapy (SRT). The purpose of this study was to evaluate the efficacy and toxicity of SRT in these patients. Fifty locally recurrent metastatic brain tumors in 47 patients were treated with SRT. The median prescribed dose of GKS was 20 Gy at the periphery. The median interval between the GKS (the last session in cases in which multiple GKS procedures were performed) and recurrence was 7.5 (range 1-33) months. Several dose-fractionation protocols were used for SRT, depending on the size and location of the tumor and previous GKS dose. The median prescribed dose of the SRT at the isocenter was 30 Gy with a median of ten fractions. Among the 50 lesions treated with SRT, 26 did not recur locally before the patient's death or the last follow-up examination, and 24 recurred locally. The median follow-up period for the surviving patients was 24 months after the first GKS procedure, and the overall survival rate was 80% at 1 year and 57% at 2 years. The median time to local re-recurrence after the SRT (16 months) was significantly longer than the median interval between the last GKS and recurrence (7.5 months; P < 0.001). Only two patients developed ≥grade 2 radiation necrosis. Stereotactic radiotherapy appeared to be an effective treatment for recurrent metastatic brain tumors and yielded relatively good local control. The associated adverse events were generally acceptable.