Cyberknife radiosurgery / radiotherapy for brain metasis: prognostic factors for local control

Purpose: Homogrnrous irradiation and delivery of fractionated radiotherapy using the CyberKnife are useful treatments for brain metastases. Here we present our results of local tumor control after CyberKnife treatment. Materials and Methods: Local tumor control was evaluated for 107 lesions in 60 patients with radiological follow-up histories longer than 1 month (range 1.1 - 36.4 months, median 6.7 months). Also, tumor shrinkage time (TST) was assessed for 98 lesions by magnetic resonance imaging. The median and mean tumor volumes per patient were 2.8 and 6.1 cm3 (range 0.1-38.4 cm3), respectivery, at the time of the intial CyberKnife treatment. The mean marginal dose was 20.1 Gy (range 11.6-24.9 Gy, median 20.3 Gy). Forty-two cases (70%) involved a single lesion, and 18 (30%) involved multiple lesions, ranging in number from 2 to 7. Results: We found no permanent symptoms resulting from radiation necrosis during the follow-up periods after CyberKnife treatment. Actuarial local control rates were 88% and 63% at 6 months, with 1year, respectively. The median time to local failure was 5.8 months., with a range of 3.0-21.9 months. TST analysis showed that large tumor volume and low marginal dose were still associated with poor tumor control. CyberKnife treatment was unable to control the tumor in 18 of 106 tumors. However, none of the patients who underwent additional radiosurgery or other surgical procedure died of brain metastasis. Conclusion: CyberKnife treatment is a useful modality which can be the first choice for treatment of brain metastasis.

CyberKnife

brain metastasis

local tumor control

tumor shrinkage time