[Radionecrosis following stereotactic radiotherapy of a 3-cm brain metastasis: Can we improve the dosimetric results?]

Stereotactic radiotherapy is a major issue in the management of brain metastases. Radionecrosis is a major concern, especially for large lesions. Optimizing dosimetric parameters is essential to allow optimal local control rate while minimizing potential toxicity. We report the case of a 30-mm brain metastases treated with stereotactic radiotherapy after initial whole brain radiotherapy, complicated with symptomatic radionecrosis. A dose of 24Gy in three fractions on the 80% isodose were delivered using a dynamic conformal arc technique (Novalis TX^®). We realized a dosimetric comparison with: (i) optimization of initial conformal arc plan, (ii) volumetric modulated arctherapy with coplanar arcs and (iii) volumetric modulated arctherapy with coplanar and non-coplanar arcs. The optimal dose planning in terms of planning target volume coverage (99.2%) and normal brain sparing (V24Gy=0.4cm³, V18Gy=6.5cm³, V10Gy=25.4cm³, V5=83.9cm³) was obtained with volumetric modulated arctherapy with coplanar and non-coplanar arcs. Volumetric modulated arctherapy-based stereotactic irradiation with coplanar and non-coplonar arcs seems an interesting option for the treatment of large brain metastases to optimize dosimetric parameters.