This study involves patients with prostate cancer who are sensitive to hormone treatment. The treatment being investigated is darolutamide, which is also known by its code names ODM-201 and BAY 1841788. Darolutamide belongs to a group of medicines called androgen receptor inhibitors, which work by blocking the effects of male hormones that can help prostate cancer cells grow. The medicine comes in the form of film-coated tablets that are taken by mouth. The purpose of this study is to see whether taking darolutamide causes an increase in a specific protein called PSMA that appears on prostate cancer cells, which could make the cancer more visible on special imaging scans.

During the study, patients will undergo PSMA PET/CT scans, which are special imaging tests that combine two types of scans to find and measure prostate cancer in the body. These scans will be done before starting the treatment and again after taking darolutamide to compare the results. The study will look at whether the number of cancer deposits increases, whether existing cancer spots show higher levels of the PSMA protein, or whether the cancer spots become larger or more visible after treatment with darolutamide. This effect, where the visibility of cancer temporarily increases after starting certain hormone-blocking treatments, is sometimes called a flare phenomenon.

Patients participating in this study will have already received previous treatment for their prostate cancer, either surgery to remove the prostate or radiation therapy, and their scans will show between one and five areas where the cancer has spread to bones or lymph nodes. The study will also collect information about any side effects that occur and how patients feel during the treatment by using quality of life questionnaires. The measurements taken during the scans will include the number of cancer spots, their size, their location in the body, and a measurement called SUVmax which indicates how much the PSMA protein is present in each spot.