Is There a Role for Dose Painting Within the Prostate in the Primal Therapy of Patients with Localized Prostate Cancer Using Choline PET/CT, Dynamic MRI and CAD or Choline MRS?

Ziele: To evaluate the role of molecular/functional imaging for the delineation of intraprostatic subvolumes for radiation therapy (IMRT, dose painting) 26 patients received a 11C choline PET/CT study and 67 patients a MR study consisting of DCE-MRI and MRS. Methode: Inclusion criteria: pathological prostate-specific antigen values (PSA) and/or previously negative transrectal ultrasound guided biopsy. Acquisition of choline PET/CT images after intravenous injection of 1112±131 MBq 11C choline. Image fusion of colored parametric maps derived from DCE-MRI and MRS (single voxel spectroscopy, SVS; chemical shift imaging, CSI) with T2 images for morphological localization. Correlation of the detected cancer lesions with histology and cytokeratin positive areas in biopsy and/or prostatectomy specimens. Ergebnis: Choline PET/CT: Sensitivity (sens.) 81%, specificity (spec.) 87%. In 1/26 (4%) patients SUVmax was detected outside the prostate cancer lesions. Using the threshold SUV of 2.65 of the receiver-operating-characteristic (ROC) curve, 6/26 (23%) patients showed a lower 11C choline uptake in up to 58–72% of the segments with cancer compared to the SUVmax of the segments with benign histopathologic lesions. DCE-MRI: Sens. 82%, spec. 89%. SVS: Sens. 55%, spec. 62%. CSI: Sens. 68%, spec. 67%. Cut-off level for PET/CT: lesions smaller 4mm and low density of cancer cells, cut-off level for DCE-MRI: lesions smaller 3mm and less than 30% cancer cells, for SVS: lesions smaller 8mm and less than 50% cancer cells), for CSI: lesions smaller 4mm and less than 40% cancer cells). In 10 patients the cancer volume as detected by MR or PET/CT was smaller than in the prostatectomy specimens, though shrinkage of the histological cancer lesion might occur due to formaline fixation. Schlussfolgerung: Till now it is questionable, if the parametric maps of DCE-MRI and MRS as well as the choline PET/CT images can be used for the delineation of intraprostatic subvolumes for radiation treatment planning (IMRT, dose painting).