Reduced-Dose SABR for Prostate Cancer

(POTEN-C Trial)

Not currently recruiting at 7 trial locations

Overseen By Sarah Neufeld

Age: 18+

Sex: Male

Trial Phase: Phase 2

Sponsor: University of Texas Southwestern Medical Center

Must not be taking: ADT, Anti-androgens

Disqualifiers: Metastatic disease, Severe comorbidity, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Prior Safety Data This treatment has passed at least one previous human trial

Compensation: Varies

Number of Visits: 5

Duration: 5 weeks

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial tests a new radiotherapy method for men with localized prostate cancer. The goal is to determine if reducing the radiation dose to certain nerves can maintain sexual function while effectively treating the cancer. Participants will receive either the standard treatment or the experimental approach, which involves a 30Gy planning target volume aimed at protecting these nerves. Men with prostate cancer that has not spread and who do not have severe urinary symptoms may be suitable for this study. As a Phase 2 trial, this research measures the treatment's effectiveness in an initial, smaller group of participants.

Do I need to stop my current medications to join the trial?

The trial protocol does not specify if you need to stop taking your current medications. However, certain medications like ADT (androgen deprivation therapy) or anti-androgen therapy are not allowed at the time of registration, and there are specific time frames for when PSA tests should not be done after stopping medications like finasteride or dutasteride.

Is there any evidence suggesting that this trial's treatments are likely to be safe?

Research has shown that stereotactic ablative body radiotherapy (SAbR) is generally well-tolerated by patients with prostate cancer. This treatment effectively targets cancer cells while protecting nearby healthy tissues, including those involved in sexual function. Consequently, it may preserve sexual function better than other treatments.

In related studies, patients receiving similar treatments have not reported major safety concerns. Advanced imaging techniques like MRI during treatment ensure high precision, reducing the risk of harming important areas around the prostate.

While side effects such as urinary or bowel issues can occur, they are usually manageable and not severe. Overall, evidence suggests that SAbR, with or without techniques to protect nerve structures, is a safe option for treating localized prostate cancer. ^{1 2 3 4 5}

Why are researchers excited about this trial's treatment?

Researchers are excited about the new SABR (Stereotactic Ablative Radiotherapy) techniques for prostate cancer because they offer a more targeted and potentially less harmful approach. Unlike traditional radiation therapy, which might affect surrounding healthy tissues, the SABR with neurovascular sparing aims to protect critical structures like the neurovascular bundle and penile bulb, potentially reducing side effects related to sexual function. This precision is achieved by carefully tailoring the radiation dose to avoid these areas while still effectively targeting the cancer. The reduced-dose SABR approach could also mean fewer treatment sessions, offering convenience and less disruption for patients.

What evidence suggests that this trial's treatments could be effective for prostate cancer?

Research has shown that stereotactic ablative body radiotherapy (SAbR), a special type of radiation therapy, can protect sexual health while effectively treating prostate cancer. In this trial, one arm involves SAbR with neurovascular sparing, a technique that preserves nerves crucial for sexual function during treatment. Studies have found that patients who received this nerve-sparing treatment reported better sexual health than those who did not. This evidence suggests that neurovascular-sparing SAbR effectively treats localized prostate cancer while maintaining important aspects of quality of life. ^{6 7 8 9 10}

Are You a Good Fit for This Trial?

Men over 18 with localized prostate cancer, good performance status, and a desire to retain sexual function. They must have a PSA ≤20 ng/ml, prostate volume ≤80 grams without severe urinary symptoms or prior treatments for prostate cancer. Participants need an adequate testosterone level and no evidence of metastatic disease.

Inclusion Criteria

My prostate cancer has a Gleason score of 7 or less.

EPIC sexual domain composite score 60-100

My cancer was confirmed by a biopsy within the last year.

Exclusion Criteria

My MRI shows disease very close to major nerves and blood vessels.

History of significant psychiatric illness

More than half of my biopsy samples tested positive for cancer.

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants receive stereotactic ablative body radiotherapy (SAbR) with or without neurovascular sparing for localized prostate cancer

5 weeks

5 visits (in-person)

Follow-up

Participants are monitored for safety, effectiveness, and quality of life outcomes after treatment

24 months

Long-term follow-up

Participants are followed for biochemical progression free survival, local recurrence, distant recurrence, and overall survival

60 months

What Are the Treatments Tested in This Trial?

Interventions

• 30Gy (Gray) planning target volume (PTV)

Trial Overview The trial is testing whether sparing neurovascular structures during stereotactic ablative body radiotherapy (SAbR) for localized prostate cancer helps maintain erectile function better than standard SAbR, while still providing effective cancer control.

How Is the Trial Designed?

Group I: SAbR WITH Neurovascular sparing Experimental Treatment 1 Intervention

* GTV represents MR defined dominant radiographic disease, if identifiable. * CTV encompasses the full prostate. At physician's discretion, the insertion of the seminal vesicle upon the prostate on slices containing prostate may be included. * PTV1\_30Gy represents a 3mm expansion on the CTV, excluding the neurovascular structures on the side to be spared (left or right). PTV1 will receive 6 Gy per fraction for 5 fractions (30 Gy). * PTV2\_SAbR40Gy OR PTV2\_SAbR45Gy will be generated by subtracting a 5mm expansion around the neurovascular elements to be spared (at least one side, left or right) from PTV1. These neurovascular structures consist of the neurovascular bundle, penile bulb, and internal pudendal arteries (see 4.1.5.2.16). PTV2 will receive 8-9 Gy per fraction for 5 fractions (40-45 Gy).

Group II: SAbR WITHOUT Neurovascular sparing Active Control 1 Intervention

* GTV represents MR defined dominant radiographic disease, if identifiable. * CTV encompasses the full prostate. At physician's discretion, the insertion of the seminal vesicle upon the prostate on slices containing prostate may be included. * PTV1\_30Gy will not be used or created on this arm * PTV2\_SAbR40Gy OR PTV2\_SAbR45Gy will be generated by a 3mm expansion on the CTV. PTV2\_SAbR will receive 8-9 Gy per fraction for 5 fractions (40-45 Gy).

Who Is Running the Clinical Trial?

University of Texas Southwestern Medical Center

Lead Sponsor

Trials

1,102

Recruited

1,077,000+

Boston Scientific Corporation

Industry Sponsor

Trials

758

Recruited

867,000+

Michael F. Mahoney

Boston Scientific Corporation

Chief Executive Officer since 2016

MBA from Wake Forest University, BBA in Finance from the University of Iowa

Kenneth Stein

Boston Scientific Corporation

Chief Medical Officer since 2020

MD from Harvard Medical School, MMSc in Clinical Investigation from Harvard-MIT Division of Health Sciences and Technology

Published Research Related to This Trial

Stereotactic ablative body radiation (SABR) is a promising non-invasive treatment for localized prostate cancer, showing similar efficacy to brachytherapy in terms of disease control and lower side effects, making it a potentially safer option.

SABR is also more cost-effective and resource-efficient compared to traditional radiation techniques, but further well-powered studies are needed to confirm its benefits before it can be considered standard care, especially for patients with metastatic disease.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Stereotactic ablative body radiotherapy in patients with prostate cancer. Loblaw, A., Liu, S., Cheung, P.[2023]

In a study of 84 low-risk prostate cancer patients treated with Stereotactic Ablative Body Radiotherapy (SABR), long-term quality of life (QOL) outcomes were generally positive, with a median follow-up of 50.8 months, although some patients reported declines in urinary (17.9%), bowel (26.2%), and sexual (37.5%) QOL domains.

Dosimetric factors such as rectal D1cc and penile bulb V35 were identified as significant predictors of worse QOL, highlighting the importance of adhering to strict dosimetric constraints to minimize side effects from treatment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dosimetric and patient correlates of quality of life after prostate stereotactic ablative radiotherapy. Elias, E., Helou, J., Zhang, L., et al.[2018]

In a study of 258 patients with localized prostate cancer treated with SABR (Stereotactic Ablative Body Radiotherapy), significant dosimetric predictors for late toxicity and quality of life (QOL) were identified, particularly focusing on high-dose regions in the bladder and rectum.

The analysis revealed that avoiding high doses in the bladder and rectum is crucial, as bladder V38 was a significant predictor of QOL, while rectal Dmax, V38, and bladder D2cc were key predictors of late toxicity, emphasizing the importance of careful dose planning in SABR treatment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dosimetric predictors of toxicity and quality of life following prostate stereotactic ablative radiotherapy. Alayed, Y., Davidson, M., Quon, H., et al.[2021]

In a study comparing two SABR treatments for prostate cancer, patients receiving 40 Gy (pHART6) had similar biochemical relapse-free survival rates to those receiving 35 Gy (pHART3), indicating that higher doses do not compromise effectiveness over time.

However, patients in the pHART6 group experienced a higher incidence of grade 2 genitourinary and gastrointestinal toxicities, suggesting that while the treatment is effective, it may come with increased side effects.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dose-escalation of five-fraction SABR in prostate cancer: Toxicity comparison of two prospective trials. Musunuru, HB., Quon, H., Davidson, M., et al.[2018]

Stereotactic ablative body radiotherapy (SABR) is an advanced treatment that delivers high doses of radiation in fewer sessions while protecting surrounding healthy tissues, making it effective for small tumors in various locations, including the prostate.

SABR is becoming a standard treatment for low and intermediate-risk prostate cancer, supported by research from Sunnybrook and the US prostate SABR consortium, highlighting its efficacy in improving patient outcomes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Evolution of hypofractionated accelerated radiotherapy for prostate cancer - the sunnybrook experience. Musunuru, HB., Cheung, P., Loblaw, A.[2022]

Stereotactic ablative radiation (SAbR) at a dose of 45 Gy in 5 fractions shows a promising safety profile for treating localized prostate cancer, with acute urinary and gastrointestinal toxicity rates of 20.4% and 7.3%, respectively, and low rates of late toxicity after 2 years.

The treatment demonstrated excellent efficacy, with a biochemical failure-free survival rate of 100% at 1 year and 98.7% at 2 years, indicating strong disease control outcomes for patients.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Dose-Intensified Stereotactic Ablative Radiation for Localized Prostate Cancer. Chen, L., Gannavarapu, BS., Desai, NB., et al.[2022]

Citations

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Prostate oncologic therapy while ensuring neurovascular ... A phase II randomized controlled trial of stereotactic ablative body radiotherapy (SAbR) with or without neurovascular sparing for erectile function ...

2. estro.org estro.org/About/Newsroom/Newsletter/Congresses/Neurovascular-Sparing-SAbR-in-Prostate-Cancer-Prel

Neurovascular-Sparing SAbR in Prostate Cancer A neurovascular-sparing approach to SBRT can preserve patient-reported sexual quality of life while maintaining oncological safety in men with localised ...

3. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC9582606/

Health-related quality of life of salvage prostate ... Between July 2013 and December 2020, 30 patients received salvage SABR for 68Ga- PSMA-11 PET/CT-detected intra-prostatic relapses. Median time ...

4. consultqd.clevelandclinic.org consultqd.clevelandclinic.org/testing-the-ability-to-preserve-erectile-function-while-using-stereotactic-ablative-body-radiotherapy-for-localized-prostate-cancer

Testing the Ability to Preserve Erectile Function While Using ... A phase 2 randomized clinical trial evaluating a nerve-sparing form of SAbR in patients with early-stage prostate cancer.

5. sciencedirect.com sciencedirect.com/science/article/pii/S2405631625000193

Neurovascular bundle sparing in hypofractionated ... Because of the low α / β of prostate cancer [1], SBRT has shown promising outcomes in the treatment of localized prostate cancer [2], [3], [4]. It utilizes high ...

6. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC11171331/

Stereotactic Body Radiotherapy (SBRT) to Localised ... This study addresses the true dose delivered in two and five treatments of the MRL and whether target objects are being met.

7. sciencedirect.com sciencedirect.com/science/article/pii/S2405630825001296

Salvage stereotactic MR-Guided adaptive radiotherapy ... Salvage SABR is an effective and safe option for LRPC, but challenges remain. •. Daily adaptation SMART enables high target coverage while sparing OAR.

8. thegreenjournal.com thegreenjournal.com/article/S0167-8140(25)04591-8/fulltext

Long-term results from a prospective registry study Magnetic resonance guided stereotactic reirradiation for locally recurrent prostate cancers: Long-term results from a prospective registry study.

9. sciencedirect.com sciencedirect.com/science/article/pii/S2405630825000497

Challenges and opportunities to minimize the dose in ... NVB sparing without compromising target coverage is feasible. No clinically relevant benefit was found for non-coplanar compared to coplanar NVB sparing plans.

10. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC2695934/

Radiotherapy treatment of early stage prostate cancer with ... IMRT plans yielded better dose conformity to the target, while proton plans achieved higher dose homogeneity, and better sparing of rectum and bladder.