Feasibility of MR-Informed Adaptive Marker-less SBRT in Patients With Bilateral Hip Prostheses Undergoing SBRT for Localized Prostate Cancer (HIP-PRO)

Hip replacements and prostate cancer are independently and both together increasing prevalent in the aging population. In the United States, the prevalence of hip prostheses among men was 1.1 million in 20101, with approximately 500,000 hip prostheses performed annually. Bilateral total hip replacement is recommended for patients with osteoarthritis affecting both hip joints. Approximately 10-25% of total hip replacement patients undergo bilateral procedures. Stereotactic body radiotherapy (SBRT) has been widely adopted as an effective treatment for localized prostate cancer, offering high precision and reduced treatment time due to conventionally fractionated radiotherapy without increasing toxicity or comprising oncological outcomes. Therefore, the use of SBRT for treatment of localized prostate cancer has significantly increased. A cohort study using data from 302 035 patients in the National Cancer Database showed that use of SBRT for prostate cancer increased from 0.2% in 2004 to 12.4% in 2020 in the United States.

However, both CT and MR-guided SBRT present unique challenges for patients with prostate cancer and bilateral hip prostheses. Metallic implants, such as hip prostheses, produce artifacts and magnetic susceptibility issues that can obscure MR imaging near the prosthetic sites, potentially complicating target contouring and planning. Given the close proximity of the prostate gland to the pelvis, which houses the hip joints, patients with bilateral hip prostheses may have significant imaging artifacts that could impair MR-guided radiotherapy quality. CT-based SBRT is less affected by metallic artifacts, but it lacks the soft-tissue resolution needed for precise prostate and OAR delineation, a gap MR imaging is uniquely positioned to fill.

Low-field MRI systems are less prone to susceptibility artifacts, including those originating from metallic implants. As a result, signal loss and distortion are expected to occur only in the immediate vicinity of the implant, making these systems particularly advantageous for imaging patients with hip implants. A prospective study quantitatively and qualitatively compared the magnitude of metal total hip arthroplasty-induced imaging artifacts in vivo between 1.5T (i.e. high-field) and 0.55T (low-field) MRI in 15 patients. Qualitative artifact magnitude was on average rated as moderate to small on 0.55T and as large to moderate on 1.5T by 2 fellowship-trained musculoskeletal radiologists. In addition, metal artifacts' areas and diameters were smaller on 0.55T when compared with 1.5T MRI for all sequences (each p>0.016).

Given the limitations of current imaging systems, the investigators propose a more flexible solution: a two-room system comprising a low-field MRI scanner for optimal image quality and a C-arm linear accelerator for rapid treatment delivery. Patient transfer between the MR device and the linear accelerator will be performed with a shuttle system which uses an air-bearing patient platform for both procedures. This setup would allow for high-quality imaging with reduced artifacts while ensuring efficient treatment times, addressing the current gap in SBRT for patients with bilateral hip prostheses. This shuttle system is MR-compatible and uses an air-bearing technology that allows the patient to be effortlessly moved by a transfer sled from MR scanner couch to linac without any movement on their part as it utilises the same patient platform with treatment using supports, immobilization devices and stereotactic tools for both procedures. This means that the patient is scanned and treated in the same position, minimising the risk of translational and/or rotational positional changes during transfer between both devices. Thus, maximum use of image-based planning data is possible. By integrating a low-field MRI scanner with a dedicated treatment delivery system, the investigators can overcome existing limitations and improve treatment precision for this growing patient population.

Study Overview

• Status: Not yet recruiting
• Conditions: Localized Prostate Adenocarcinoma
• Intervention / Treatment: Radiation: Low-field MR-informed adaptive marker-less SBRT for definitive treatment of localized prostate cancer in patients with bilateral hip prostheses

• Study Type: Interventional
• Enrollment (Estimated): 13
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Matthias Guckenberger, Prof. Dr. med.; Phone Number: +41442553566; Email: Matthias.Guckenberger@usz.ch
• Study Contact Backup: Name: Tiuri E. Kroese, Dr. med.; Phone Number: +41442553566; Email: tiuri.kroese@usz.ch

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Diagnosis of localized prostate cancer suitable for definitive SBRT based on a multidisciplinary tumour board recommendation and / or clinical practice guideline.
• Presence of bilateral hip prostheses labeled as MR safe or MR-conditional.
• ECOG performance status ≤ 2.
• Signed informed consent.
• Age ≥18 years -

Exclusion Criteria:

• Large body size that would not fit into the MRI-simulator bore
• Hip prosthesis that are labeled as MR unsafe;

• Contraindications to MRI including but not limited to:

  • Claustrophobia unmanageable by sedation
  • Electronic devices such as pacemakers, defibrillators, deep brain stimulators, cochlear implants that are labeled as MR unsafe, electronic devices labeled as MR safe or MR conditional are not a contraindication;
  • Metallic foreign body in the eye or aneurysm clips in the brain;
• Clinically significant concomitant diseases that would interfere with the study (e.g. hepatic dysfunction, cardiovascular disease).
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc.
• Enrolment of the investigator, his/her family members, employees and other dependent persons.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Single group study; Assessment of low-field MR-informed adaptive marker-less SBRT for definitive treatment of localized prostate cancer in patients with bilateral hip prostheses.	Radiation: Low-field MR-informed adaptive marker-less SBRT for definitive treatment of localized prostate cancer in patients with bilateral hip prostheses; Low-field MR-informed adaptive marker-less SBRT

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
MR-informed online adaptive definitive SBRT for localized prostate cancer	Evaluate the feasibility of MR-informed online adaptive definitive SBRT for localized prostate cancer using MR simulation and CBCT-based treatment delivery in patients with bilateral hip prostheses.	From enrollment to the end of treatment

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Treatment toxicity	Treatment toxicity measured with Common Terminology Criteria for Adverse Events (CTCAE), version 5.0.	During treatment and up to 5 years after treatment, or death of the patient
Image quality	Difference in image quality and adapted contours as compared between 1.5 T and 0.55 T field strength MR scanners used for pre-treatment and intra-treatment simulation	During treatment
Patient's wellbeing and comfort	Patients will be asked to report their comfort after simulation assessed with a 0 to 10 Numerical Rating Scale (NRS), with 0 representing complete absence of discomfort to 10 representing extreme discomfort.	During treatment
Physicians decision certainty	Clinicians will be asked to report their clinical confidence with a 0 to 10 NRS, with 0 representing complete absence of clinical confidence to 10 representing extreme clinical confidence	During treatment

Collaborators and Investigators

• Sponsor: University of Zurich
• Investigators: Principal Investigator: Matthias Guckenberger, Prof. Dr. med., University of Zurich

Study record dates

Study Major Dates

• Study Start (Estimated): February 9, 2026
• Primary Completion (Estimated): September 30, 2028
• Study Completion (Estimated): September 30, 2031

Study Registration Dates

• First Submitted: June 10, 2025
• First Submitted That Met QC Criteria: June 24, 2025
• First Posted (Actual): June 29, 2025

Study Record Updates

• Last Update Posted (Actual): February 9, 2026
• Last Update Submitted That Met QC Criteria: February 4, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: prostate cancer; SBRT; Stereotactic body radiotherapy; Bilateral hip prostheses
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Genital Neoplasms, Male; Urogenital Neoplasms; Neoplasms by Site; Neoplasms; Genital Diseases, Male; Prostatic Diseases; Male Urogenital Diseases; Prostatic Neoplasms
• Other Study ID Numbers: RAO-25-004; 2025-01091 (Other Identifier: Swissethics)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No