Non Invasive Methods for Differential Diagnosis Radionecrosis/Recurrence After Radiosurgery of Brain Metastases

The purpose of the study is to assess a diagnostic strategy by monitoring brain metastases after radio surgical treatment . Data from two non-invasive techniques: PET-FET (positron emission tomography using 1-Fluoro-Ethyl-Tyrosine) and MSR (magnetic resonance spectroscopy) will be compared to histological examination (gold standard) in patients with active persistent and increased lesion 4 months after radiosurgery. The study should develop a decision-making algorithm based on non-invasive tests and allow improving the length and quality of life of these patients.

Early differential diagnosis between relapse and radio necrosis after radiosurgery would allow:

• To perform resection of tumor relapse
• To treat feasable/inoperable tumor relapse with a salvage radiosurgery
• To avoid irradiation for patients presenting radiation necrosis
• To reduce the corticosteroid prescription period. Validation of non-invasive diagnostic tools should in fine avoid biopsy. In addition, the results of this study should help to better estimate the true incidence of radiation necrosis and better specify the predictors of this complication.

CV-METANEC is a prospective, multicenter, open, multidisciplinary study involving the following departments: neurosurgery, neuroradiology, nuclear medicine and neuropathology.

4 centers participating in the study: Groupe Hospitalier Pitié-Salpêtrière University Hospital, Lariboisière Hospital, Lille University Hospital of Clermont Ferrand and Toulouse University Hospital.

Patients are included if they were treated by radiosurgery for one or more brain metastases. The interval between the radiosurgical treatment and the inclusion is at least 6 months. The lesion is clinically and / or MRI evolving.

The criterion used to measure the discriminating power of the algorithm to rank the differential between recurrences with or without radionecrosis or only radionecrosis is the area under the ROC (receiver operating characteristic) curve. The inclusion of 90 subjects will achieve a standard deviation of the area under the curve 0.04.

The duration of study participation will be five weeks, from inclusion until the end of hospitalization. Subsequently, the patient will be followed as usual.

Inclusion D0: whether the conditions of inclusion are applied, the patient signs the consent form and exams before surgery are planned: SRI-MRI, examination of scintigraphy and anesthesia consultation.

D15: MRI (neuroradiology) and anesthetic consultation (neurosurgery).

D30-D33 (+/- 7 days): 3 days of hospitalization:

D30: MRI / MRS always done before-FET PET D31: stereotactic biopsy for histological samples. D33: CT scan before the patient is discharged. Total study duration: 5 years