Radioinduced effects in patients with brain metastases treated with CyberKnife® platform radiosurgery

Abstract

The damage associated to stereotactic radiotherapy and radiosurgery is edema and radionecrosis of the brain by magnetic resonance images (MRI), so it is paramount to analyze the factors that contribute to it. Methods: This retrospective study included patients with brain metastases that were treated with radiosurgery or stereotactic radiotherapy using CyberKnife® between July 2012 and December 2013, with respect to these criteria: primary disease controlled, functional status KNF >70%, and a maximum of two lesions without mass effect. We analyzed the MRI obtained after their treatment and every three months in order to determine possible changes. Results: The most frequent finding was breast cancer Her2/Neu biotype, 83% of the patients with supratentorial location, 33% of patients had received previously whole-brain radiotherapy, and 60% had > 5 cc tumoral volume. The dosimetric parameters included a median of isodose line of 88%, median conformality index of 1.4, median homogeneity index of 1.13 and a median V14Gy of 23 cm3. MRI showed that 83% of the patients developed edema in various grades; of the 17% who reported clinical symptoms none surpassed grade 1 central nervous system toxicity of the Radiation Therapy Oncology Group (RTOG) classification. According to our findings in the analyzed, only V14Gy > 5 cm3 seems to be related to an increase in the edema volume. Conclusions: MRI and clinical (minimal) changes were related to the volume of normal brain tissue included in the higher-dose areas of radiation.