Dose De-escalation in Prostate Radiotherapy Using an MR-Linac in Two Fractions

NCT07391982 | Recruiting

• 1 other identifier: M24DTI
• Study Type: interventional
• Target: 54
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this clinical trial is to find out whether lowering the radiation dose to parts of the prostate without visible tumor on MRI can reduce side effects while still effectively treating prostate cancer in men with low or intermediate-risk prostate cancer. The main questions it aims to answer are:

• Does reducing the radiation dose to healthy prostate tissue lower the risk of bowel and urinary side effects?
• Can we maintain good cancer control by keeping a high dose for MRI-visible tumor areas? Researchers will compare two treatment approaches:
• One group receives a uniform high dose to the entire prostate.
• The other group receives a lower dose to healthy prostate tissue and a high dose only to visible tumor areas. Participants will:
• Receive two sessions of MRI-guided radiotherapy using an MR-Linac.
• Complete questionnaires about urinary, bowel, and sexual health before and after treatment.
• Have follow-up visits to monitor side effects and PSA levels for up to 2 years.

Conditions

Prostate Cancer (Adenocarcinoma)

Keywords

De-escalation; Radiotherapy; MR-Linac

Outcome Measures

Primary Outcomes (1)

• Acute GU toxicity

  Physician-reported acute Grade 2 or higher CTCAE GU toxicity observed within 13 weeks of starting radiotherapy

  within 13 weeks of starting radiotherapy

Secondary Outcomes (9)

• Dosimetry

  During Radiotherapy treatment of 8 days

• Late GI toxicity

  1 and 2 years after radiotherapy treatment

• Biochemical relapse-free survival

  2 years

• Severity of erectile dysfunction experienced by patient

  Before radiotherapy treatment, and at 6, 12 and 24 months after radiotherapy treatment

• Acute GI toxicity

  At baseline, after the last fraction, and 2, 4 and 12 weeks after radiotherapy treatment

Study Arms (2)

Uniform dose SBRT

OTHER

Radiation: uniform dose radiotherapy

De-escalated dose SBRT

OTHER

Radiation: De-escalated dose radiotherapy

Interventions

uniform dose radiotherapy RADIATION

27 Gy dose in 2 fractions to the whole prostate+/- seminal vesicles with a 0mm PTV margin using MR-linac

Uniform dose SBRT

De-escalated dose radiotherapy RADIATION

The benign prostate +/- SV CTV will receive 20 Gy in 2 fractions with a 0mm PTV margin using MR-linac. The intraprostatic tumor masses (on MRI) will receive 27 Gy in 2 fractions. A 4mm GTV to PTV margin will be added to the in-traprostatic MR visible tumour to form PTV 27Gy.

De-escalated dose SBRT

Eligibility Criteria

• Age: 18 Years+
• Sex: male
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Men aged ≥18 years
• Histological confirmation of prostate adenocarcinoma requiring radical radiotherapy
• Gleason score 3+3, 3+4 or 4+3 (ISUP Grade groups (GG) 1, 2 or 3)
• MRI-visible tumour(s) of PIRADS v2 grade 3 or higher and able to be delineated on T2 and diffusion-weighted imaging +/- dynamic contrast-enhanced imaging. Tumour nodule visible on MRI should be considered able to be boosted by treating clinician and \<2.5cm in maximal dimension. MRI must be performed within 3 months of trial entry
• The MRI-defined lesion must be confirmed as malignant on biopsies (any Gleason grade is sufficient as long as Gleason score is reported).
• MRI stages mT1 and T2 or mT3a with ≤ 1mm tumour outside gland AND otherwise favourable intermediate risk characteristics (Gleason 3+3, 3+4)(as staged by AJCC TNM 2018)
• PSA \<20 ng/ml prior to starting androgen deprivation therapy (ADT).
• WHO Performance status 0-2
• Ability of the participant to understand and the willingness to sign a written informed consent (IC) form.
• Ability/willingness to comply with the patient reported outcome questionnaires schedule throughout the study.

You may not qualify if:

• Contraindications to MRI (e.g. pacemaker, potentially mobile metal implant, claustrophobia)
• IPSS Score \> 19
• High grade disease (GG3) occult to MRI-defined lesion. As a guide, any pathology for which you would consider surveillance is allowed outside of the MRI-defined area.
• Prostate volume \>90cc
• Comorbidities which predispose to significant toxicity (e.g. inflammatory bowel disease) or preclude long term follow up
• Hip replacement, or other pelvic metalwork which causes artefact on diffusion-weighted imaging
• Previous pelvic radiotherapy
• Patients needing \>6 months of ADT due to disease parameters.
• Previous invasive malignancy within the last 2 years excluding basal or squamous cell carcinomas of the skin, low risk non-muscle invasive bladder cancer (assuming cystoscopic follow up now negative) or small renal masses on surveillance.

Sponsors & Collaborators

• The Netherlands Cancer Institute: lead
• MRL Consortium: collaborator
• Elekta Limited: collaborator

Study Sites (1)

The Netherlands Cancer Institute

Amsterdam, 1066CX, Netherlands

RECRUITING

MeSH Terms

Conditions

Prostatic Neoplasms; Adenocarcinoma

Condition Hierarchy (Ancestors)

Genital Neoplasms, Male; Urogenital Neoplasms; Neoplasms by Site; Neoplasms; Genital Diseases, Male; Genital Diseases; Urogenital Diseases; Prostatic Diseases; Male Urogenital Diseases; Carcinoma; Neoplasms, Glandular and Epithelial; Neoplasms by Histologic Type

Central Study Contacts

Floris Pos, MD, PhD

CONTACT

+31205129111; f.pos@nki.nl

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: October 2, 2025
• First Posted: February 6, 2026
• Study Start: November 17, 2025
• Primary Completion (Estimated): February 1, 2027
• Study Completion (Estimated): December 1, 2028
• Last Updated: February 6, 2026

Record last verified: 2026-02

Data Sharing

• IPD Sharing: Will share
• Time Frame: 5 years

Locations

NL (1)