This diagnostic clinical trial will be conducted according to a randomized, prospective, controlled, double-arm, single-centre design. The control will be implemented by comparing the PET/MRI results with the histopathological finding after radical prostatectomy (positive state), the assumed absence of a relevant prostate cancer focus if PET/MRI guided biopsy and standard biopsy are negative (negative state) and/or the detection of a biochemical tumor relapse [rising prostate specific antigen (PSA) after PSA nadir; secondary objective].

In the last years magnetic resonance imaging (MRI) as well as positron emission tomography (PET) of the prostate have emerged as promising imaging tools. MRI provides mainly morphologic information and, to an increasing degree, functional information on the tumor microenvironment by using multiparametric approaches leading to an increase in diagnostic accuracy. Transition and periurethral zone cancers and the identification of patients' individual risk (e.g. for the development of a metastatic disease after primary treatment) is still a limitation of this method. PET, concerning radiolabelled choline, provides functional and predicting data on tumor metabolism and aggressiveness and has been found to be of complimentary value to morphologic imaging but still with the caveat of false positive and false negative findings. To overcome these limitations of morphological and functional imaging techniques, hybrid imaging systems have been developed and introduced into clinical routine. Additionally, the recently developed 68Ga-labeled Prostate Specific Membrane Antigen (PSMA) provides a highly specific information on a possible metastatic spread of prostate cancer. Thus the combined use of PET-MRI has wide spread applications in prostate cancer diagnosis, staging and treatment planning.

The potentials of this novel technique in general and its impact on assessing patients' individual risk to support a therapy or active surveillance decision in a future modified urological patient management were not yet explored in detail, but an initial prospective clinical trial in 38 patients with a sequential PET/MRI technique demonstrated the ability of a significant improvement of the individual methods. This registered prospective, randomized clinical trial is intended to proof, in a first step, the superiority of PET/MRI vs. the actual clinical standard procedures by applying a stable multiparametric metabolic hybrid imaging protocol. The aim of this study is to reduce the number of unnecessary invasive procedures to a minimum (image guided biopsy) and to enable superior image guided risk stratification.

In this prospective, randomized, multi-arm, multi-treatment clinical trial 220 subjects will be included at 1 site within 3 years. With a maximum follow-up for an early biochemical relapse of 2 years the planned duration should not exceed 5 years. The primary objective will be answered after 36 months.

Inclusion Criteria:

• blood PSA level > 4.0 ng/ml and
• free-to-total PSA ratio <22% and/or
• progressive rise of PSA levels in two consecutive blood samples despite antibiotics

Exclusion Criteria:

• antiandrogen therapy
• prostate needle biopsy <21 days before PET/MRI
• known active secondary cancer
• endorectal coil not applicable (e.g. anus praetor with short rectal stump)
• known active prostatitis (e.g. painful DRE)
• known anaphylaxis against gadolinium-DOTA
• patient's written informed consent not given
• needle biopsy and/or prostatectomy compound not available for histology/immunohistochemistry