ESTRO 2025 congress report | Clinical track
Proffered Papers Session on Monday 5 May 2025

Report by the ESTRO Urology Focus Group

Erectile dysfunction (ED) remains one of the most impactful and common long-term toxicities that develops after radiotherapy for localised prostate cancer. While stereotactic body radiotherapy (SBRT) offers a high-precision, hypofractionated approach with excellent disease control, its potential for collateral damage to organs critical to erectile function is a significant concern. Advances in imaging and treatment delivery optimisation have enabled the use of strategies selectively to spare key anatomical structures that are associated with sexual function. The prostate oncologic therapy while ensuring neurovascular conservation (POTEN-C) trial, which is a multi-centre, patient-blinded, phase II randomised controlled trial (NCT03525262), is intended to assess whether a neurovascular-sparing approach to SBRT can preserve patient-reported sexual quality of life while maintaining oncological safety in men with localised prostate cancer.¹

Dr Neil Desai, USA, Principal Investigator, presented at ESTRO 2025 the initial results of the POTEN-C trial. He explained that advances in radiation oncology that can help to preserve sexual function include: improved MRI that can be used to delineate anatomy; higher precision stereotactic ablative radiotherapy (SAbR); better understanding of which organs-at-risk are implicated in sexual function; and novel planning approaches with hydrogel spacers.

The trial's innovative approach uses MRI staging to identify patients with at least one side of the prostate within 5mm of the neurovascular bundle without a prostate imaging-reporting and data system (PIRADS) 3-5 lesion. The neurovascular-sparing technique involves delivery of a reduced dose of 30Gy to the area around the neurovascular bundle while therapeutic dosing of 40-45Gy is maintained to the remainder of the prostate.

Dr Desai acknowledged that there was some uncertainty about exactly which structures were being spared: "We're not really sure what we're sparing, right? We don't know if it's a neurovascular bundle, we don't know if it's a penile bulb or internal penile arteries. We are trying to spare a sector at least, maybe get the musculature as well at the same time."

So far, the trial has enrolled 120 men with localised prostate cancer and intact baseline sexual function (as measured by the expanded prostate cancer index composite (EPIC)). Participants have been randomised 1:1 to either standard SAbR or to neurovascular-sparing SAbR, with patient blinding maintained throughout.

At the three-month assessment (with 118 evaluable patients), physician-graded acute genitourinary and gastrointestinal toxicities were similar between arms, with no grade 3 or higher toxicities observed. However, patient-reported outcomes showed advantages for the neurovascular-sparing approach.

The neurovascular-sparing arm has demonstrated significantly better scores for urinary irritative/obstructive symptoms (mean 91 vs. 86, p=0.02) and improved sexual domain scores (mean 71 vs. 67, p=0.10). When examining changes from baseline, neurovascular-sparing SAbR showed smaller mean decreases in sexual function (-6.8 vs. -11.7), bowel function (-0.15 vs. -3.29), and urinary irritative/obstructive symptoms (-1.77 vs. -6.25) compared with conventional SAbR.

Particularly notable were the findings regarding minimally important differences in quality of life. Use of the neurovascular-sparing approach led to significantly reduced bowel domain changes at three months (19% . 37%, p=0.03). Among patients treated with the higher 45Gy radiation dose, changes in urinary obstructive/irritative (26% vs. 58%, p=0.04) and incontinence domains (11% vs. 40%, p=0.04) also significantly favoured the neurovascular-sparing approach.

Dr Desai contextualised these findings by referencing recent surgical literature that reported a 39% recovery of erectile function at 12 months with enhanced neurovascular-sparing surgical techniques. He noted that radiation oncology has often had "an area of a lot of nihilism" regarding sexual function preservation, but these results suggest that progress is possible.

The primary endpoint analysis of two-year sexual function outcomes is expected next year. However, these three-month results are already encouraging. Dr Desai concluded that "neurovascular-sparing SAbR facilitated by MRI planning mitigated acute quality-of-life changes" compared with standard approaches, suggesting that this innovative technique has the potential to impact clinical practice significantly by better balancing cancer control with quality-of-life preservation.

Prof Thomas ZILLI

Department of Radiation Oncology

Oncology Institute of Southern Switzerland, EOC

Bellinzona, Switzerland
ESTRO Urology Focus Group

 

References

¹ Desai NB, Dess RT, Hannan R, et al. Preliminary results of a phase II randomized control trial of neurovascular-sparing SAbR in localized prostate cancer [PCa] (POTEN-C, NCT03525262)

Presentation Number: E25-1650