Patients With Metastasized Prostate Cancer Whose Prostate-specific Antigen-level (PSA) Remains >0,2 ng/ml After Six Months of Dual Antihormonal Therapy Will Receive Radiotherapy to the Prostate and Radiotherapy to Refractory Metastases

RIALTO: Radiotherapy in Primarily Metastasized Prostate Cancer - Image-guided Local AbLaTion of Prostate and Oligoresidual Disease

The goal of this clinical trial is to learn if radiotherapy to the prostate and PET-positive (positron emission tomography) metastasis will lead to radiological response on PSMA-PET (prostate specific membrane antigen-PET). Patients who receive combined androgen deprivation therapy for de novo metastasized prostate cancer and show an incomplete PSA-response (>0,2 ng/ml after six months) and exhibit at least four bone metastases on PET-imaging at this time point (without metastases to organs) can take part in this study.

The main questions it aims to answer are:

• Does radiotherapy to the prostate and PET-positive metastases lead to a radiological response one year after radiotherapy? Researchers will analyze PET-imaging prior to radiotherapy to the prostate and metastases and one yeare thereafter.

Participants will:

• Continue taking combined androgen-deprivation therapy
• Receive a total of three PSMA-PET/CT scans
• Receive radiotherapy to the prostate and PET-positive metastases
• Visit the clinic every three months for 36 months
• Complete quality of life questionnaires at every visit

Inclusion Criteria:

• Prostate adenocarcinoma
• de novo metastasized prostate cancer (at least 4 osseous metastases +/- lymphonodal metastases)
• first-line combined antihormonal therapy (ADT + ARPI) for six months
• PSA > 0,2 ng/ml after six months of combined ADT/ARPI therapy
• multimetastasized disease stage without visceral metastases on imaging at first diagnosis (PET, CT, or bone scan)
• <16 osseous/lymphnodal metastases on response assessment imaging (PSMA-PET/CT) after six months of combined antihormonal therapy

Exclusion Criteria:

• neuroendocrine histology
• visceral metastases (M1c)
• prior radiotherapy to the pelvis
• PSA < 0,2 ng/ml after 6 months of combined antihormonal therapy
• prior prostatectomy
• contraindication against PSMA-PET/CT and/or radiotherapy to the prostate/metastases
• HIFU or TUR-P within 6 months of study treatment
• other active malignancy two years prior to study inclusion (except skin cancer in remission)
• relevant GU/GI condition (active fistula or other)
• known tumor predisposition syndrome