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NCT Number: NCT07644754

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

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

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Key information

Conditions

Prostate Cancer Genital Diseases Genital Diseases, Male Genital Neoplasms, Male Male Urogenital Diseases Neoplasms Neoplasms by Site Prostate Cancer Metastatic Disease Prostate Cancer Metastatic to Bone Prostatic Diseases Prostatic Neoplasms Urogenital Diseases Urogenital Neoplasms

Age range

18 year–85 year

Sex eligibility

Male

Study type

Interventional

Phase

Not applicable

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Radiotherapy to the prostate and to PSMA-PET positive metastases

Radiation

Patients will receive radiotherapy to the prostate and to PSMA-PET postivie Metastases

Primary outcomes

  1. Radiological Progression-Free Survival

    Time frame: 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

  1. Lesion-specific response on imaging

    Time frame: 12 months after radiotherapy to metastases

  2. Prostate specific antigen (PSA)

    Time frame: up to 36 months after radiotherapy to the prostate

    Prostate specific antigen

  3. Objective response rate

    Time frame: 12 months after radiotherapy to metastases

  4. Time to next systemic therapy

    Time frame: up to 36 months after radiotherapy to the prostate

  5. Overall survival

    Time frame: up to 36 months after radiotherapy to the prostate

  6. Failure-free survival

    Time frame: up to 36 months after radiotherapy to the prostate

  7. Progression-free survival

    Time frame: up to 36 months after radiotherapy to the prostate

  8. Metastasis-free survival

    Time frame: up to 36 months after radiotherapy to the prostate

  9. Prostate-cancer specific survival

    Time frame: up to 36 months after radiotherapy to the prostate

Other outcomes

  1. Quality of life questionnaires

    Time frame: up to 36 months after radiotherapy of the prostate

    EORTC QLQ-C30 Prostate

  2. Organ-specific side effects

    Time frame: up to 36 months after radiotherapy of the prostate

    CTCAEv5

  3. Organ function

    Time frame: up to 36 months after radiotherapy of the prostate

    IPS-Score

  4. Choice of next systemic therapy

    Time frame: up to 36 months after radiotherapy to the prostate

    Documentation of systemic treatment in case of progression

  5. Reason for change in systemic therapy

    Time frame: up to 36 months after radiotherapy to the prostate

    Documentation in case of change in systemic therapy

  6. Quality of Life questionnaire

    Time frame: up to 36 months after end of radiotherapy of the prostate

    QLQ-PR25

  7. Quality of life questionnaire

    Time frame: up to 36 months after radiotherapy to the prostate

    EQ-D5

  8. Organ-specific side effects

    Time frame: up to 36 months after end of radiotherapy

    RTOG questionnaire

  9. Organ function

    Time frame: up to 36 months after radiotherapy to the prostate

    ICIQScore

  10. Organ-specific function

    Time frame: up to 36 months after radiotherapy to the prostate

    NCI-PRO-CTCAE

  11. Organ-specific function

    Time frame: up to 36 months after radiotherapy to the prostate

    IIEF

Study contacts

Contact information is provided by the study sponsor or research team.

Elgin Hoffmann, MD, Dr. med.

CONTACT

[email protected]

4970712982165

Maximilian Niyazi, MD, Prof. Dr. Dipl.-Phys.

CONTACT

Sponsors and collaborators

Lead sponsor

University Hospital Tuebingen

Other

Collaborators

  • Ludwig-Maximilians - University of Munich
  • Uniklinikum Giessen und Marburg
  • University Hospital Augsburg
  • University Hospital Dresden
  • University Hospital Freiburg

Registry information

Official study title

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

Acronym: RIALTO

Important dates

Study start
2026
Primary completion
2027
Study completion
2031
First posted
Jun 12, 2026
Registry last updated
Jun 12, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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