A Study of 68Ga-GRP PET/CT for Imaging in Low and Intermediate Risk Prostate Cancer

Patients with primary low and intermediate risk prostate cancer (PCa) for whom radical prostatectomy are indicated, will be invited to participate to the present study.

The aim of this study is to investigate the clinical value of 68Ga-GRP positron emission tomography / computed tomography (PET/CT) compared to 68Ga-PSMA PET/CT in patients with low and intermediate risk PCa.

Prostate cancer (PCa) is the second-most common cancer among men across the world, and a significant cause of death in many regions. Different stages of PCa directly affect both the therapeutic schedule and patient prognosis.

Recommended imaging modalities for initial staging include computerized tomography (CT) scan, bone scan, and Magnetic Resonance Imaging (MRI). In addition to initial work-up, Gallium-68 prostate-specific membrane antigen positron emission tomography/computer tomography (68Ga-PSMA PET/CT) is a relatively new nuclear imaging modality, showing high sensitivity and specificity. Recently, several studies have investigated the role of 68Ga-PSMA PET/CT in a first-line diagnostic setting, especially in patients with high-risk and biochemically recurrent PCa.

Therefore, PET imaging with 68Ga-PSMA may participate to optimize work-up in the staging of high-risk patients.

Another family of radiopharmaceuticals aimed to target the Gastrin-Releasing Peptide Receptor (GRP-R) which is overexpressed in early stage PCa. Various radiolabeled GRP analogues have been developed and shown encouraging results as related to the detection of primary PCa in preclinical study. However, 68Ga-GRP failed to detect some bone metastases in hormone-refractory patients. A prospective study identified that GRPR expression is not associated with Gleason score (GS) and PSMA expression, suggesting that 68Ga-GRP and 68Ga-PSMA PET/CT may be complementary in various risks of PCa diagnosis.

The aim of this pilot study is to compare 68Ga-PSMA PET/CT to 68Ga-GRP PET/CT in patients with PCa of low and intermediate risk to better understand how 68Ga-PSMA and 68Ga-GRP PET/CT could performed a primary lesion mapping and how 68Ga-PSMA and 68Ga-GRP PET/CT could be used (or combined) in clinical practice.

Eligibility Criteria:
Inclusion Criteria:

* patients divided in :

  * Patients with low risk prostate cancer (Gleason score ≤ 6 and cT1-T2a and Prostate Specific Antigen (PSA) value \< 10 ng/mL);
  * Patients with intermediate risk prostate cancer (Gleason score 7 or cT2b or PSA value 10-20 ng/mL);
  * Patients with high risk prostate cancer (Gleason \> 7 or cT2c or PSA value \> 20 ng/mL);
  * Candidate for radical prostatectomy after discussion in multidisciplinary committee;
  * Written informed consent willingly obtained.

Exclusion Criteria:

* Any kind of previous treatment for prostate cancer (hormonal treatment, EBRT, brachytherapy, cryotherapy, etc...);
* Patient not candidate for radical prostatectomy and/or unable to benefit from surgery;
* Patient under legal protection or unable to express its own consent;
* Patient within exclusion period from another clinical trial;
* Claustrophobia (unable to accept PET/CT scanning).