Main Session
Sep 29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement

3322 - Vascular Optimized Radiotherapy Tuned to Critical Structures for Erectile Function Using High-Precision X-Ray Treatment (VORTEX) - A Prospective Phase III RCT of Neurovascular-Sparing SBRT

02:15pm - 03:30pm ET
Poster Hall - Exhibit Hall A
Screen: 22
POSTER

Presenter(s)

Jonathan Massachi, MD, MS - University of California, Los Angeles, Los Angeles, CA

J. Massachi1, L. Valle2, M. Xiang1, K. Taparra2, S. K. M. Lau1, S. Eleswarapu3, D. Maziero4, D. Ruan1, J. M. Lamb5, D. O'Connell5, D. Telesca6, M. L. Steinberg2, J. B. Weidhaas2, and A. U. Kishan2; 1Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, 2Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, 3Department of Urology, University of California, Los Angeles, Los Angeles, CA, 4University of California, Los Angeles - Department of Radiation Oncology, Los Angeles, CA, 5UCLA, Department of Radiation Oncology, Los Angeles, CA, 6Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, Los Angeles, CA

Purpose/Objective(s):

Large studies of stereotactic body radiotherapy (SBRT) for prostate cancer have demonstrated that approximately 30% of patients will experience at least grade 2 erectile dysfunction following treatment. This is hypothesized to be driven primarily by dose to the neurovascular bundles, internal pudendal arteries, and corpus cavernosa. Exploratory analysis from the MIRAGE clinical trial of MRgSBRT with 2mm planning margins versus CT-guided SBRT with 4 mm margins suggested that the improved sexual function outcomes noted in the trial may have been driven by an unintentional reduction in low intermediate-dose exposures to the internal pudendal arteries. Intentional vascular-sparing approaches have been preliminarily explored, including 18-month results from the non-randomized phase II ERECT trial (with adaptive MRgSBRT in all patients) and 3-month results from the randomized phase II POTEN-C trial (with nonadaptive CT-guided SBRT in all patients). Given the benefit of aggressive margin reduction and potential benefits of adaptive therapy, it is important to rigorously evaluate how the combination of these approaches might be leveraged to improve sexual function after SBRT.

Materials/Methods:

This is a phase III, randomized, single-blind trial designed to determine whether neurovascular-sparing SBRT improves patient-reported sexual function outcomes (EPIC-26 sexual function domain) when measured at 24 months as compared to conventional SBRT without explicit NV-sparing. Patients eligible for this trial will have well-lateralized, histologically-confirmed non-metastatic prostate adenocarcinoma. It is anticipated that 30% of patients receiving prostate SBRT without explicit NV-sparing will experience a clinically significant decrement in EPIC-26 sexual function domain scores at 2 years post-treatment. An overall sample of 200 patients (100 per arm) will provide 80% power to detect a reduction of 20% in the proportion of patients who experience a clinically significant decrement in EPIC-26 sexual function domain scores using a one-sided, two sample Z-test at 0.025 significance level. This trial differs from and builds upon prior and ongoing investigations in several ways. First, it pre-specifies stratification for the use of hormone therapy, baseline sexual medications, radiotherapy platform (CT vs. MRI), and adaptive therapy use (yes vs. no), which will allow robust evaluation of the impact of intentional NV-sparing. Finally, all patients will undergo novel MRI sequences to help delineate relevant OARs, regardless of randomization arm. The trial is currently open for enrollment as of January 2026 and is actively accruing patients.

Clinical trial registry number NCT07293585.

Results:

Not required

Conclusion:

Not required