3236 - Expanding Ultra-Hypofractionated Radiotherapy: A 12-Fraction, 51.6Gy Regimen for Locally Advanced and Node-Positive Prostate Cancer

12:45pm - 02:00pm PT

Hall F

Screen: 13

POSTER

Presenter(s)

Alina Goltser, MD - Sheba Medical Center, Ramat Gan, Dan

A. Goltser, I. Tamir, I. BarOrian, R. Lewin, J. Mattout, M. ben-Ayun, S. Dubinski, D. Benjamin, J. Kraitman, I. Weiss, Y. Lawrence, Z. Symon, and L. Hammer; Radiation Oncology Department, Sheba Medical Center, Ramat Gan, Israel

Purpose/Objective(s):

The radiobiological benefit of ultra-hypofractionated radiation therapy (RT) regimens in the treatment of prostate cancer (PCa) is widely accepted. While RTOG 0938 demonstrated the safety and efficacy of RT delivered in 12 fractions to a dose of 51.6 Gy to the prostate only in low-risk PCa patients, it did not incorporate prostate-specific membrane antigen positron emission computer tomography (PSMA PET/CT) at initial staging, nor did it include higher risk patients or the combination of RT with androgen deprivation therapy (ADT). We hypothesized that delivery of 51.6 Gy in 12 fractions in locally advanced or node positive PCa patients provides favorable disease control with an acceptable toxicity profile.

Materials/Methods:

We performed a retrospective chart review of all patients treated with 51.6 Gy in 12 fractions between August 2014 and April 2024 at our institution. Exclusion criteria included RT dose other than 51.6 Gy, less than three months follow up, and metastatic disease. Toxicity was assessed according to Common Terminology Criteria for Adverse Events version 5. Endpoints were biochemical-recurrence free survival, and distant-metastases free survival.

Results:

A total of 220 patients treated with 51.6 Gy in 12 fractions were eligible for analysis.

The median follow-up duration was 20 months (range, 3–88), with a median age of 75 years (IQR, 9.0). A third of patients presented with T3 / T4 disease. Of 220 patients, 29.5% had unfavorable intermediate risk, 26.3% had high risk, 21.2% had very high risk and 13.4% had node-positive disease.

At baseline, 208 patients (94.5%) underwent PSMA PET/CT, and 176 (80.0%) underwent mpMRI. SpaceOAR implantation was performed in 129 patients (58.6%), while fiducial markers were placed in 209 (95.0%). All patients were treated by means of volumetric modulated arc therapy with daily IGRT. Elective nodal irradiation (ENI) was performed in 187 patients (85.0%) to a dose of 36Gy. ADT was administered to 175 patients (79.5%) for a median duration of 9 months (range, 2-24). Abiraterone was added to ADT in 12.9% of patients. Only one patient presented with acute grade 3 toxicity. Late Grade 2 genitourinary )GU( and gastrointestinal )GI( toxicity were observed in 7.3% and 2.7%, respectively. Late Grade 3 toxicity occurred in 1.4%, including one proctitis, and two urinary retention episodes. No late Grade 4 or 5 GU or GI treatment-related toxicity was observed. At the end of follow-up, biochemical-recurrence free survival was 96.8%, and distant-metastases free survival was 97.7%. There were no prostate cancer-related deaths.

Conclusion:

With a short follow up, a 12-fraction ultra-hypofractionated radiotherapy regimen delivering 51.6 Gy to the prostate demonstrated promising disease control and an acceptable toxicity profile in locally advanced prostate cancer.