68Ga-PSMA-11 PET/MRI for Selecting Men With Prostate Cancer for Focal Therapy

Prostate cancer is one of the most commonly diagnosed cancers in men. For patients with localized, clinically significant disease, focal therapy has emerged as a minimally invasive treatment option that targets only the cancerous portion of the prostate while preserving surrounding healthy tissue. Compared with whole-gland treatments such as radical prostatectomy or radiation therapy, focal therapy has the potential to reduce treatment-related side effects, including urinary incontinence and erectile dysfunction, while maintaining cancer control in appropriately selected patients.

The success of focal therapy depends on accurately identifying all clinically significant prostate cancer within the prostate before treatment. Multiparametric magnetic resonance imaging (MRI) is currently the standard imaging modality used to evaluate patients being considered for focal therapy. Although MRI has substantially improved prostate cancer detection and localization, clinically significant tumors may remain undetected. Failure to identify all clinically significant disease may result in incomplete treatment, persistent cancer outside the treated area, or disease recurrence following focal therapy.

Prostate-specific membrane antigen (PSMA) is a protein that is highly expressed on the surface of most prostate cancer cells. Radiotracers that target PSMA, such as 68Ga-PSMA-11, allow prostate cancer lesions to be visualized using positron emission tomography (PET). When PET is combined with MRI in a hybrid PET/MRI scanner, molecular information from PET is integrated with the high-resolution anatomical detail provided by MRI. Previous studies have demonstrated that combining PSMA PET with MRI improves the detection of clinically significant prostate cancer compared with MRI alone, but the value of this approach for selecting patients for focal therapy has not been established.

This prospective pilot study will evaluate the diagnostic performance of 68Ga-PSMA-11 PET/MRI compared with MRI alone in men with localized intermediate-risk prostate cancer who have already elected to undergo radical prostatectomy as part of their standard clinical care. Because the prostate gland will subsequently be removed, detailed whole-mount histopathological examination of the surgical specimen can be used as the reference standard to determine the true location and extent of cancer throughout the prostate. This provides a unique opportunity to directly compare imaging findings with pathology.

Imaging findings from MRI alone and from integrated PET/MRI will be independently interpreted and compared with whole-mount histopathology to determine how each imaging strategy would influence patient selection for focal therapy. The study will assess whether additional lesions detected by PET/MRI would alter eligibility for focal therapy or require modification of the planned treatment strategy. The analysis will evaluate theoretical focal therapy approaches, including targeted, zonal, and hemi-gland ablation, based on the distribution of clinically significant disease identified on surgical pathology. Participants will not receive focal therapy as part of this study, and PET/MRI findings will not influence their clinical management.

The investigators hypothesize that 68Ga-PSMA-11 PET/MRI will improve identification of clinically significant prostate cancer compared with MRI alone and more accurately identify patients who are appropriate candidates for focal therapy. Improved patient selection has the potential to reduce treatment failures caused by undetected cancer outside the intended treatment area while preserving the quality-of-life benefits associated with focal therapy.

As a pilot feasibility study, the results will provide preliminary evidence to inform the design of a larger prospective clinical trial. If the findings demonstrate improved diagnostic performance, 68Ga-PSMA-11 PET/MRI may become an important imaging tool for patient selection in future focal therapy programs and clinical trials, ultimately supporting more individualized treatment planning for men with localized prostate cancer.

Inclusion criteria

• Ability to provide written informed consent.
• Age 18 years or older.
• Clinically significant prostate cancer (csPCa) with clinical stage ≤ T2c and planned radical prostatectomy.
• Serum prostate-specific antigen (PSA) ≤ 20 ng/mL.
• Clinically significant prostate cancer within an MRI-visible lesion, defined as - International Society of Urological Pathology (ISUP) Grade Group 2 or 3 (Gleason score 3+4 or 4+3) in any biopsy core.

Exclusion criteria

• Inability to lie still for the PET/MRI examination.
• Known contraindication or hypersensitivity to gallium Ga 68 gozetotide (68Ga-PSMA-11) or to the MRI gadolinium contrast agent, including any component of the formulation.