An interventional study of Daily Adaptive MR-Enhanced SBRT with Neurovascular Bundle Sparing in Prostate Cancer, Localized Prostate Carcinoma and Low-Risk Prostate Cancer, sponsored by University of Zurich. Not yet recruiting at 1 site in Switzerland. Open to male participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-04.
Sponsored by University of Zurich · Not applicable, Interventional, and Treatment
Radiotherapy is a standard and highly effective treatment for prostate cancer that is confined to the prostate gland. One modern approach, called stereotactic body radiotherapy (SBRT), delivers treatment in just five sessions and has been shown to control prostate cancer as well as longer treatment schedules. Large clinical studies have demonstrated excellent cancer control rates after SBRT.
Although SBRT is effective, some men experience worsening erectile function after treatment. Researchers believe that reducing radiation exposure to the nerves and blood vessels involved in erections, known as the neurovascular bundles (NVBs), may help preserve sexual function.
The EF-PRESERVE study is evaluating whether a specialized MRI-guided treatment approach can safely reduce radiation dose to these structures while still delivering effective treatment to the prostate cancer.
Stereotactic body radiotherapy (SBRT) has evolved from an experimental modality into a guideline-supported treatment option for localized prostate cancer. Initial pooled consortium data across 1,100 patients demonstrated high efficacy and acceptable toxicity, which was subsequently confirmed by prospective phase III trials. The HYPO-RT-PC trial established the non-inferiority of 42.7 Gy in seven fractions, while PACE-B showed that 5-fraction SBRT without androgen deprivation therapy (ADT) achieved equivalent 5-year biochemical or clinical failure-free survival compared to conventional or moderately hypofractionated schedules (95.8% vs. 94.6%). Nevertheless, erectile dysfunction remains a frequent late toxicity, with clinician-reported CTCAE Grade more than 2 erectile dysfunction rising from 18% at baseline to 26.4% five years post-SBRT in PACE-B.
To mitigate this functional decline, the EF-PRESERVE study incorporates daily adaptive magnetic resonance imaging (MRI). Because standard cone-beam computed tomography (CBCT) lacks sufficient soft-tissue resolution to visualize structures like the neurovascular bundle (NVB), the ARTEMIS workflow acts as a scaleable alternative to integrated MR-linacs.
Patients are scanned on a dedicated MRI simulator to adjust target and NVB contours daily, then transferred via a dedicated shuttle system directly to a CE-marked CBCT linear accelerator for radiotherapy delivery.
7,046 studies on the registry are indexed under Prostatic Neoplasms; 1,580 are open to participants now.
This study's planned enrollment of 48 is below the median of 60 across 5,348 interventional studies indexed under Prostatic Neoplasms.
Browse Prostatic Neoplasms studies →University of Zurich is the lead sponsor of 1,049 studies on the registry; 133 are open to participants now.
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confirmed, low- or intermediate risk localized prostate cancer eligible for definitive prostate SBRT according to NCCN criteria as (Appendix 1):
If ADT planned during radiotherapy:
Exclusion Criteria:
High risk localized prostate cancer according to NCCN criteria as:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CTCAE grade
The US National Cancer Institute’s scale of how severe an adverse event is — any unwanted medical event during a study, such as a symptom, an illness or an abnormal test result, whether or not a treatment caused it. Whether it did is judged separately.
“Side effects of earlier treatment resolved to grade 1 or less” means they have settled to mild or gone.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants undergo ultra-hypofractionated stereotactic body radiotherapy (SBRT) delivered in 5 fractions. Prior to each fraction, patients are imaged on a MRI simulator to evaluate and adapt target volumes and neurovascular bundle (NVB) contours. Using the ARTEMIS transfer shuttle system, patients are moved directly to a standard C-arm CBCT linear accelerator. The NVB will be spared during radiotherapy delivery while maintaining a minimum target dose of 40 Gy to the dominant intraprostatic lesion (DIL). If clinically indicated, concurrent short-course androgen deprivation therapy (under 6 months) is limited strictly to oral GnRH antagonists (e.g., Relugolix).
Radiation: Daily Adaptive MR-Enhanced SBRT with Neurovascular Bundle Sparing
Patients receive daily adaptive ultra-hypofractionated SBRT (5 fractions) utilizing the ARTEMIS workflow. Before each fraction, patients undergo low-field MRI to adapt target and neurovascular bundle (NVB) contours based on daily anatomical changes. Patients are transferred in treatment position to a standard CBCT linear accelerator via a shuttle system. Radiotherapy intentionally spares the NVB (unilaterally or bilaterally depending on tumor proximity) to preserve erectile function, while ensuring the dominant intraprostatic lesion (DIL) receives at least 40Gy. Additional erection-related structures (internal pudendal artery, penile bulb, corpus cavernosum) are contoured for dosimetric analysis. Concurrent short-course ADT (not more than 6 months), if indicated, is restricted to oral GnRH antagonists (Relugolix) to allow rapid testosterone recovery.
Proportion of Patients with CTCAE v6.0 Grade ≥2 Erectile Dysfunction at 1 Year Post-SBRT
Evaluates the proportion of sexually active patients who develop clinician-reported moderate to severe erectile dysfunction (defined as CTCAE v6.0 Grade ≥2) 1 year following the completion of adaptive MR-enhanced prostate SBRT with neurovascular bundle (NVB) sparing. The rate will be evaluated against historical controls from the PACE-B trial benchmark.
Time frame: 1 year post-SBRT
Patient-Reported Erectile Function Change via IIEF-5 Score
Evaluates changes in patient-reported erectile function using the 5-item International Index of Erectile Function (IIEF-5) questionnaire. Scores range from 5 to 25, with lower scores indicating more severe erectile dysfunction (ED). The mean score change from baseline, the proportion of patients maintaining potency, and the proportion experiencing a clinically meaningful decline (≥4 point drop in IIEF-5 score) will be evaluated across time points.
Time frame: Baseline, every 3 months for the first 1 year, and annually thereafter up to 5 years post-SBRT
Biochemical progression-free survival
Measurement of PSA, biochemical progression is defined according to phoenix criteria.
Time frame: Baseline, every 3 months for the first 1 year, and annually thereafter up to 5 years post-SBRT
Plan to share: Undecided
Start is estimated for Dec 2026; primary completion for Dec 2029, 36 months later.
Of 1,098 non-industry interventional studies with no phase under Prostatic Neoplasms, half reached primary completion within 43 months of starting (the median), counting those still running; a quarter within 22 and three quarters within 86. This study's planned 36 months is below that.
Counting every sponsor, half of 1,155 studies reached it within 43 months; a quarter within 22 and three quarters within 84.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
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