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

NCT07644754 — Not applicable, Not yet recruiting, 27 participants, University Hospital Tuebingen

ClinicalTrials Daily · Areas · Conditions · Drugs · Sponsors ·

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

Registry	NCT07644754, acronym RIALTO
Status	Not yet recruiting
Phase	Not applicable
Study type	Interventional; na, single group, masking: none, other
Enrollment	27 (Estimated)
Sponsor	University Hospital Tuebingen (Other); collaborators: Ludwig-Maximilians - University of Munich, University Hospital Freiburg, University Hospital Dresden, Uniklinikum Giessen und Marburg, University Hospital Augsburg
Conditions	Prostate Cancer, Prostate Cancer Metastatic Disease, Prostate Cancer Metastatic to Bone
Interventions	Radiotherapy to the prostate and to PSMA-PET positive metastases (Radiation)
Dates	start 2026-07-01 (estimated), primary completion 2027-07-01 (estimated), completion 2031-02-01 (estimated), first posted 2026-06-12, last updated 2026-06-12

-Summary

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

Expand all sections · Collapse all

+Arms and interventions

Arm	Type	Interventions	Description
Radiotherapy to the prostate and PSMA-PET/CT guided radiotherapy of refractory metastases	Experimental	Radiation: Radiotherapy to the prostate and to PSMA-PET positive metastases	Radiotherapy to the prostate and refractory metastases on PSMA-PET/CT

Radiotherapy to the prostate and to PSMA-PET positive metastases (Radiation): Patients will receive radiotherapy to the prostate and to PSMA-PET postivie Metastases

+Outcome measures

Primary outcomes

Radiological Progression-Free Survival [12 months after radiotherapy of metastases]: Radiological Progression-Free Survival as determined on PSMA-PET/CT according to RECIP criteria, defined as 30% response in PSA-volume

Secondary outcomes

Lesion-specific response on imaging [12 months after radiotherapy to metastases]
Prostate specific antigen (PSA) [up to 36 months after radiotherapy to the prostate]: Prostate specific antigen
Objective response rate [12 months after radiotherapy to metastases]
Time to next systemic therapy [up to 36 months after radiotherapy to the prostate]
Overall survival [up to 36 months after radiotherapy to the prostate]
Failure-free survival [up to 36 months after radiotherapy to the prostate]
Progression-free survival [up to 36 months after radiotherapy to the prostate]
Metastasis-free survival [up to 36 months after radiotherapy to the prostate]
Prostate-cancer specific survival [up to 36 months after radiotherapy to the prostate]

Other outcomes

Quality of life questionnaires [up to 36 months after radiotherapy of the prostate]: EORTC QLQ-C30 Prostate
Organ-specific side effects [up to 36 months after radiotherapy of the prostate]: CTCAEv5
Organ function [up to 36 months after radiotherapy of the prostate]: IPS-Score
Choice of next systemic therapy [up to 36 months after radiotherapy to the prostate]: Documentation of systemic treatment in case of progression
Reason for change in systemic therapy [up to 36 months after radiotherapy to the prostate]: Documentation in case of change in systemic therapy
Quality of Life questionnaire [up to 36 months after end of radiotherapy of the prostate]: QLQ-PR25
Quality of life questionnaire [up to 36 months after radiotherapy to the prostate]: EQ-D5
Organ-specific side effects [up to 36 months after end of radiotherapy]: RTOG questionnaire
Organ function [up to 36 months after radiotherapy to the prostate]: ICIQScore
Organ-specific function [up to 36 months after radiotherapy to the prostate]: NCI-PRO-CTCAE
Organ-specific function [up to 36 months after radiotherapy to the prostate]: IIEF

+Eligibility

Sex: Male, ages: 18 Years to 85 Years

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

+Study documents

Study Protocol (PDF, 2025-10-17)

+Investigators

Elgin Hoffmann, MD, Principal investigator, Department of Radiation Oncology, University Hospital Tübingen