Target definition in salvage postoperative radiotherapy for prostate cancer: 18F-fluorocholine PET/CT assessment of local recurrence.

PURPOSE: Inadequate clinical target volume (CTV) definition is likely to be a major contributing factor to local recurrence (LR) rate after radiotherapy. Our aims were to identify sites of prostate cancer LR in biochemical recurrence post-prostatectomy using 18F-Fluorocholine (18F-FCH) positron emission tomography/computed tomography (PET/CT) and to compare different CTV-delineation guidelines in a cohort of postoperative patients. MATERIAL AND METHODS: Thirty-six patients presenting with LR within the prostatic bed on 18F-FCH PET/CT between 10/2011 and 06/2016 were included in this retrospective study. Median PSA at the time of 18F-FCH PET/CT was 2.7 ng/mL (0.8-9.4) and median PSA doubling time was 11 months (3-28). For each patient, the CTVRTOG, CTVFROGG and CTVEORTC following the corresponding guidelines were outlined and compared. Forty-one LR were delineated using a gradient-based method and the percentage of FCH uptake included in each CTV was evaluated. RESULTS: The anastomosis was the most common recurrence site (52.8%), followed by the retrovesical region (31.7%) and the bladder neck (7%). The median SUV max value was 4.8 (2.3-16.1). The percentage of LR entirely included in the CTVRTOG was not significantly different from that included in the CTVFROGG (84% versus 83%, p = .5). Significantly more recurrences were included in the CTVRTOG volume compared to the CTVEORTC (84% versus 68%, p=.006), due to a better coverage of the bladder neck and retrovesical regions. Six out of 10 relapses occurring in the posterior region of the anastomosis were not covered by any of the CTVs. CONCLUSIONS: In our study, the CTVRTOG and CTVFROGG ensured the best coverage of LR seen on 18F-FCH PET/CT. When outlining the prostatic fossa, greater coverage of the posterior vesico-urethral region may allow better coverage of potential microscopic disease.

Prognostic value of 18F-FET PET/CT in newly diagnosed WHO 2016 high-grade glioma.

O-(2-[F]fluoroethyl)-L-tyrosine positron-emission tomography/computed tomography (F-FET PET/CT) is well known in brain tumor management. Our study aimed to identify the prognostic value of F-FET PET/CT in high-grade gliomas (HGG) according the current 2016 World Health Organization (WHO) classification.Patients with histologically proven WHO 2016 HGG were prospectively included. A dynamic F-FET PET/CT was performed allowing to obtain 2 static PET frames (static frame 1: 20-40 minutes and static frame 2: 2-22 minutes). We analyzed static parameters (standard uptake value [SUV]max, SUVmean, SUVpeak, TBRmax, TBRmean, tumoral lesion glycolysis, and metabolic tumoral volume) for various isocontours (from 10% to 90%). PET parameters, clinical features, and molecular biomarkers were compared with progression-free survival (PFS) and overall survival (OS) in univariate and multivariate analysis.Twenty-nine patients were included (grade III n = 3, grade IV n = 26). Mean PFS and OS were, respectively, 8.8 and 13.9 months. According to univariate analysis, SUVmean, SUVpeak, TBRmax, and TBRmean were significantly correlated with OS. In static 1 analysis, TBRmax seemed to be the best OS prognostic parameter (P = .004). In static 2 analysis, TBRmean was the best parameter (P = .01). In static 1 analysis, only SUVpeak was significant (P = .05) for PFS. Good performance status (PS < 2; P < .0001) and extent of resection (P = .019) identified the subgroup of patients with the best OS. Only TBRmax (P = .026) and extent of resection (P = .025) remained significant parameters in multivariate analysis.Our data suggested that high TBRmax seemed to be the most significant OS independent prognostic factor in patients with newly diagnosed HGG.