Radionécrose après radiothérapie stéréotaxique d'une métastase cérébrale de 3 cm : la technique peut-elle améliorer les résultats dosimétriques ?

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 24 Gy 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 (V24 Gy = 0.4 cm3, V18 Gy = 6.5cm3, V10 Gy = 25.4 cm3, V5 = 83.9 cm3) 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.