Five-fraction CyberKnife radiotherapy for large brain metastases in critical areas: impact on the surrounding brain volumes circumscribed with a single dose equivalent of 14 Gy (V14) to avoid radiation necrosis

Abstract

The efficacy and toxicity of five-fraction CyberKnife radiotherapy were evaluated in patients with large brain metastases in critical areas. A total of 85 metastases in 78 patients, including tumors >30 cm3 (4 cm in diameter) were treated with five-fraction CyberKnife radiotherapy with a median marginal dose of 31 Gy at a median prescribed isodose of 58%. Changes in the neurological manifestations, local tumor control, and adverse effects were investigated after treatment. The surrounding brain volumes circumscribed with 28.8 Gy (single dose equivalent to 14 Gy: V14) were measured to evaluate the risk of radiation necrosis. Neurological manifestations, such as motor weakness, visual disturbances and aphasia improved in 28 of 55 patients (50.9%). Local tumor control was obtained in 79 of 85 metastases (92.9%) during a median follow-up of eight months. Symptomatic edema occurred in 10 patients, and two of them (2.6%) required surgical resection because of radiation necrosis. The V14 of these patients was 3.0–19.7 cm3. There were 16 lesions with a V14 of ≥7.0 cm3, and two of these lesions developed extensive brain edema due to radiation necrosis. None of the patients with a V14 of <7.0 cm3 exhibited edema requiring surgical intervention. We therefore conclude that a high rate of local tumor control and low rates of complications can be obtained after five-fraction CyberKnife radiotherapy for large metastases in critical areas. The V14 of the surrounding brain is therefore a useful indicator for the risk of radiation necrosis in patients with large metastases.

Target volume geometric change and/or deviation from the cranium during fractionated stereotactic radiotherapy for brain metastases: Potential pitfalls in image guidance based on bony anatomy alignment

“…Some investigators recommend that even large tumours should be treated with limited (3-5) fractions in as short a period as possible to circumvent TDD. Although the data regarding the dosimetric factors relevant to radiation necrosis in FSRT are limited, as pre-viously mentioned, 4,5,12,13 increased fractionation is deemed imperative for large tumours to ensure the safety of treatment. 5,20 Non-consecutive delivery could also exploit the radiobiological advantage of FSRT for facilitating tumour reoxygenation.…”

“…Although the data regarding the dosimetric factors relevant to radiation necrosis in FSRT are limited, as pre-viously mentioned, 4,5,12,13 increased fractionation is deemed imperative for large tumours to ensure the safety of treatment. 5,20 Non-consecutive delivery could also exploit the radiobiological advantage of FSRT for facilitating tumour reoxygenation. 20,21 The following provisions for the execution of FSRT for BM are recommended: expeditious commencement after planning image acquisition, volume-based selection of fractions (increased fraction number for larger tumours and vice versa) and unenhanced image surveillance during treatment for previously described situations, although the dose fractionation scheme should be finely tailored to each patient in consideration of other predictive factors affecting survival, such as the patient's Karnofsky performance status.…”

“…Stereotactic irradiation has retained a pivotal role in the management of limited brain metastases (BM), for which more durable local control and lower toxicity than previously achieved are desired, given that improved systemic therapies may be able to control extracranial active disease more efficiently, thereby leading to prolongation of survival for patients harbouring BM . To overcome the limitations of single‐fraction radiosurgery for large lesions, fractionated stereotactic radiotherapy (FSRT) has increasingly been applied . Furthermore, given the limitation of hypofractionated SRT to 3–5 fractions for larger tumours, FSRT in >5 fractions may be adopted to ensure the efficacy and safety of treatment.…”

“…To overcome the limitations of single‐fraction radiosurgery for large lesions, fractionated stereotactic radiotherapy (FSRT) has increasingly been applied . Furthermore, given the limitation of hypofractionated SRT to 3–5 fractions for larger tumours, FSRT in >5 fractions may be adopted to ensure the efficacy and safety of treatment. However, the increase in number of fractions and the intervening weekend holidays inevitably prolong the overall treatment period.…”

Image-Guided Hypofractionated Radiosurgery of Large and Complex Brain Lesions

“…Patient performance status and preoperative neurologic deficits reportedly improved in 57.1 and 70.6%, respectively. Another study [42] evaluating the efficacy and toxicity of 5-fraction CK radiotherapy in patients with large brain metastases in critical areas, demonstrated that a high rate of local tumor control and low rate of complications are achievable. They report a local tumor control rate of 92.9% during a median follow-up of 8 months and report that neurological manifestations improved in 50.9% of the patients.…”