S. Tomatis

O2.02ROLE OF AN INTEGRATED IMAGING FOR TARGET VOLUME DEFINITION AND RADIOTHERAPY PLANNING IN PATIENTS WITH DIAGNOSED HIGH GRADE GLIOMA

PURPOSE: To evaluate the impact of FLAIR/MRI and 11C-MET PET for high grade glioma (HGG) tumor volume delineation on radiotherapy (RT) planning. End point is local and systemic toxicity, local control and patients survival. n nMETHODS AND MATERIALS: Patients with diagnosis of HGG underwent CT scan, MRI and 11CMET-PET for RT planning were included. Surgery, concomitant chemo-radiotherapy and adjuvant chemotherapy (CT) were performed in all patients. Clinical Target Volume was delineated on enhanced T1-MRI (CTV1) and on FLAIR-MRI images (CTV2) that were compared between them. Planning Target Volume (PTV1 and PTV2) was generated enlarging CTV1 and CTV2 of 20 mm and 10 mm respectively; also Biological Target Volume (BTV) was delineated. Plans were optimized using volumetric modulated arc therapy (VMAT). Response and toxicity were recorded. n nRESULTS: From November 2011 to June 2013, 69 patients were evaluated. MET-PET uptake was visible in all cases after surgery. In 50% of patients part of BTV was outside of the PTV1 up to 32 mm, while in all cases BTV was inside of the PTV2. No severe toxicities were recorded. Recurrence in the same site of treatment occurred in 38/69 (55%) patients at a median time of 13 months (range 5-14 months) all in field. With a median observation time of 16 months (range 6-21 months) 57 patients (84%) are alive and 11 (16%) dead. DFS and OS at 1 and 2 years were 63 % and 33%, 87% and 82% respectively. Extent of resection (EOR) and MGMT promoter methilation significantly affected survival (p< 0.01). n nCONCLUSION: Our data suggest that target volume definition using FLAIR-MRI is more adequate for target definition compared with enhanced T1MRI. This approach allows a better target coverage and increased normal brain sparing. Besides, uptake 11C-METPET could help to identify microscopic residual risk areas that should need higher radiation therapy doses.