Preoperative Staging and Dose Escalated Radiotherapy of Prostate Carcinoma With PET and MRI

Overview

Prostate cancer (PCa) is currently the most common neoplastic disease among men in well-developed countries with 350 000 new cases diagnosed annually in Europe and 4 800 in Finland. Due to widespread use of serum prostate specific antigen (PSA) in asymptomatic men, most patients present initially with localized disease. Radical prostatectomy, radiotherapy (RT) and active surveillance are the most common management options for patients with localized PCa. Proper preoperative staging for patients with adverse features on biopsy who are candidates for radical prostatectomy is urgently needed. For elderly men external beam RT is the preferred modality which can be safely performed utilizing modern techniques such as intensity modulated and image guided radiotherapy (IMRT and IGRT). Since randomized studies suggest a dose response effect beyond 78-80 Gy newer techniques aim at dose escalation provided that toxicity can be controlled. Therefore, ultra high dose IMRT/IGRT requires visualization of intracapsular disease which will receive the highest dose. Taken together, the use of accurate anatomical and functional imaging modalities are essential for planning both nerve sparing radical prostatectomy and ultra high dose IMRT/IGRT Fluorine-18 labeled L-leucine analogue 1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC) has shown to preferentially accumulate in PCa and its nodal metastases. By assisting in localization of intraprostatic and pelvic disease FACBC with hybrid positron emission tomography/computed tomography (PET/CT) or magnetic resonance imaging (PET/MRI) has potential to improve selection of patients for robot-assisted radical prostatectomy and IMRT/IGRT. Anatomical MRI at 1.5 Tesla (T) compared with transrectal ultrasound has demonstrated a higher sensitivity for tumor detection but almost the same specificity, stressing the need for additional metabolic MRI. Advanced application of MRI such as proton magnetic resonance spectroscopy (1H MRS), diffusion weighted imaging (DWI) and dynamic contrast enhanced imaging (DCE-MRI) are increasingly being used for detection and characterization of PCa. The use of 3T scanners and multiparametric MRI (mpMRI), consisting of anatomical MRI, DWI, 1H MRS and DCE-MRI, demonstrated very promising result for staging and detection of PCa.

Specific aims of the current study are as follows: i) To determine the sensitivity, specificity and accuracy of multiparametric 3T MRI, (anatomical MRI, DCE-MRI, DWI and 1H MRS) combined with FACBC PET/CT and PET/MRI in correlation with systematic biopsy and whole mount prostatectomy specimens. ii) To asses the applicability of multiparametric 3T MRI combined with FACBC-PET/CT and PET/MRI for detection of cancer aggressiveness based on Gleason score and PSA. iii) To develop quantitative and qualitative methods for evaluation of FACBC PET/MRI iv) To develop and validate an imaging protocol which will become the standard protocol for prostate imaging both for surgical and radiotherapy patients at Turku PET Centre using hybrid PET/MRI