A volumetric study of CyberKnife hypofractionated stereotactic radiotherapy as salvage for progressive malignant brain tumors: initial experience.

ABSTRACT

OBJECTIVE: Radiosurgery is frequently offered to patients with progressive malignant brain tumors if radiation therapy or chemotherapy fails to provide local control. The use of single-shot regimens, however, is limited by the risk of complications when the tumor is large, surrounded by edema or has been pre-treated with radiation. Hypofractionation may confer safety but has not been tested for these difficult tumors. We report the results of hypofractionation as an alternative option in a small cohort of progressive malignant brain tumors. METHODS: Hypofractionated CyberKnife radiotherapy was chosen for 18 progressive malignant brain tumors (six high-grade gliomas and 12 metastatic lesions) in 15 patients because of size, previous treatment with radiation or surrounding edema. The mean dose was 21 +/- 4 Gy and the number of fractions was 5 +/- 0.6. The volume of each tumor at treatment was compared with the volume at follow-up. RESULTS: Thirteen of the 18 tumors (72%) showed a volume decrease. The average volume change was a decrease of 16 +/- 58% (median 20%) with a follow-up of 180 +/- 121 days (median 172 days). Toxicity occurred in only one patient, with symptoms improving on steroids. DISCUSSION: Progression of malignant brain tumors not ideal for single-shot radiosurgery can be arrested or reversed, at least for short periods, with minimal toxicity using hypofractionated radiotherapy. Longer studies will be needed to assess durability of this response in these difficult tumors.