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

Overview

Focal therapy is a minimally invasive treatment option for some men with localized prostate cancer. Unlike surgery or radiation, focal therapy treats only the area of the prostate containing clinically significant cancer, with the goal of preserving urinary and sexual function. Successful focal therapy depends on accurately identifying all areas of clinically significant prostate cancer before treatment. Currently, multiparametric magnetic resonance imaging (MRI) is the standard imaging method used to determine whether a patient is a suitable candidate for focal therapy. However, MRI may miss some clinically significant cancers, which can lead to incomplete treatment. This pilot study will evaluate whether 68Ga-PSMA-11 positron emission tomography/magnetic resonance imaging (PET/MRI) can improve the selection of men with localized prostate cancer for focal therapy compared with MRI alone. The study will enroll men with intermediate-risk prostate cancer who are already planning to undergo radical prostatectomy as part of their standard care. Participants will receive a single injection of 68Ga-PSMA-11 followed by a PET/MRI scan before surgery. The PET/MRI findings and MRI findings will be reviewed separately and compared with the prostate tissue examined after surgery, which serves as the reference standard for determining the true location and extent of cancer. The main question this study is trying to answer is whether 68Ga-PSMA-11 PET/MRI is more accurate than MRI alone in identifying men who are appropriate candidates for focal therapy. The study will also evaluate whether PET/MRI detects more clinically significant prostate cancer lesions than MRI alone. Researchers hypothesize that 68Ga-PSMA-11 PET/MRI will improve the detection of clinically significant prostate cancer and more accurately identify patients who are suitable candidates for focal therapy, potentially reducing the risk of untreated cancer remaining in the prostate after treatment. If successful, the results of this pilot study will support the development of a larger clinical trial and may help improve future treatment planning for men with localized prostate cancer.

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.