18F-PSMA-1007 PET Imaging to Detect Primary Prostate Cancer

Prostate cancer (PCa) is the second most common diagnosed malignancy in males worldwide, with over 1.2 million new patients diagnosed every year. Since the introduction of prostate-specific antigen (PSA) the primary diagnosis consisted of histologic confirmation by transrectal ultrasound (TRUS) systematic biopsies. However, in recent years this has changed into performing multi-parametric MR imaging (mpMRI) prior to prostate biopsy. MpMRI has proven to be a valuable tool to avoid unnecessary prostate biopsies and prevent over-treatment of low-grade PCa, while maintaining equal or higher detection rates of high-grade PCa. Prostate MRI is evaluated using the Prostate Imaging-Reporting and Data System (PIRADS). Lesions are given a category score, from 1 (high-grade PCa is unlikely to be present) to 5 (presence of high-grade PCa is highly likely). A PIRADS 3 is an equivocal scan. Nonetheless, mpMRI has room for improvement as its specificity for high-grade tumors is only 73% and local staging is limited with mpMRI. Also, the mpMRI is frequently unclear as 4-39% of detected lesions are classified as PIRADS 3. Prostate-specific membrane antigen receptor (PSMA) is highly overexpressed by 95% of the prostate cancer cells and seem to positively correlate to aggressiveness of the tumor. PSMA-positron emission tomography (PET) uses this feature by visualizing PSMA expressing prostate tumors. Currently, the PSMA-PET is generally used to detect recurrences or metastases. However, there is an increasing interest for PSMA-PET scans in patients with a primary diagnosis of PCa for staging purposes. Yet, there is no published data on the role of PSMA-PET on PCa prior to biopsy in comparison to the detection rate of mpMRI and histopathology. This study aims to investigate the added value of a 18F-PSMA-PET to mpMRI in the detection of local prostate cancer lesions. 75 patients with the suspicion on prostate cancer (e.g. elevated PSA and/or abnormal digital rectal exam) will receive a 18F-PSMA-1007 PET following mpMRI. 25 patients with PIRADS 1-2 (probably benign disease), 25 patients with PIRADS 3 (equivocal disease) and 25 patients with PIRADS 4-5 (highly suspicious for malignancy) will be included in this study. If either the mpMRI or 18F-PSMA-1007 PET shows a potential malignant lesion, a (target) biopsy will be performed.