Main Session

Sep 29

PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement

3269 - Comparable Early Outcomes With Moderately Hypofractionated Versus Conventional Secondary Radiotherapy After Prostatectomy

02:15pm - 03:30pm ET

Poster Hall - Exhibit Hall A

Screen: 9

POSTER

Presenter(s)

Kendall Garrett, MD, BS - Case Western Reserve School of Medicine, Cleveland, OH

K. N. Garrett¹, S. Lichtman-Mikol², K. V. Chaung³, K. A. D'Rummo⁴, S. Roy⁵, M. Patel⁶, N. G. Zaorsky³, R. Zuhour⁷, T. Weisent⁸, D. E. Spratt⁹, and A. Y. Jia²; ¹Case Western Reserve School of Medicine, Cleveland, OH, ²Department of Radiation Oncology, University Hospitals Cleveland Medical Center/ Seidman Cancer Center, Cleveland, OH, ³Department of Radiation Oncology, University Hospitals Seidman Cancer Center, Case Western Reserve University, Cleveland, OH, ⁴University of Kansas School of Medicine, Department of Radiation Oncology, Kansas City, KS, ⁵Rush University Medical Centre, Chicago, IL, ⁶University Hospitals, Cleveland, OH, ⁷The University of Texas Medical Branch, Galveston, TX, ⁸University Hospitals Seidman Cancer Center, Cleveland, OH, ⁹University Hospitals Seidman Cancer Center, Case Western Reserve University, Cleveland, OH

Purpose/Objective(s):

Early secondary radiotherapy (sRT) is the preferred postoperative strategy for most patients with biochemical recurrence following prostatectomy, but the optimal dose for moderately hypofractionated sRT remains uncertain. We hypothesize that early sRT using 55 Gy/20f provides similar freedom from progression (FFP) and adverse events compared with conventional fractionation.

Materials/Methods:

We performed a retrospective review of patients treated with sRT following prostatectomy between 05/2021 and 12/2025 at a single institution. Patients received either conventional fractionation (66 Gy/33f) or a moderately hypofractionated regimen (55 Gy/20f). The primary endpoint was FFP, defined as biochemical failure per Phoenix criteria (PSA =2 ng/mL above nadir), clinical failure (local, regional, or distant), or death from any cause. Twelve-month FFP was estimated using Kaplan–Meier methods and compared using the log-rank test. Adverse events were dichotomized into baseline and within 4 years post-sRT; and the highest CTCAE v5 grade was compared using Fisher’s exact test.

Results:

A total of 150 patients were analyzed (66 Gy/33f; n=88; 55 Gy/20f, n=62), with 20 FFP events. Baseline characteristics were well balanced, including median age (66 yr), median pre-sRT PSA (0.31 ng/mL), = GG4 (24.7%), pT3 disease (75.3%), pN0 (82.7%), and concurrent ADT use (63.3%). Time from surgery to sRT was longer in the 55 Gy/20f group compared to 66Gy/33f (28.4mo vs 18.5mo, p=0.043). At a median follow-up of 20.5 months (IQR 13.4–30.0), 12-month FFP was similar between fractionation schedules: 96.4% (95% CI 92.6–100.0) for 66 Gy/33 f and 98.4% (95% CI 95.3–100.0) for 55 Gy/20f (p=0.52). Baseline Grade 1-2 genitourinary (GU) and gastrointestinal (GI) events were comparable between groups. Late Grade 3 GU events attributable to sRT occurred in 3.4% (66 Gy/33f) vs 3.2% (55 Gy/20f) patients (p=1.00). Late Grade 3 GI event rates were similarly low (1.1% in 66 Gy/33f vs 3.2% in 55 Gy/20f; p=0.60). No prostate cancer–related deaths were observed.

Conclusion:

Moderately hypofractionated sRT demonstrates comparable short-term efficacy and toxicity to conventional fractionation in patients with recurrence following prostatectomy.

Table

	Baseline			Post RT (within 4 yr)
	66Gy/33f (n=88)	55Gy/20f (n=62)	P-value	66Gy/33f (n=88)	55Gy/20f (n=62)	P-value
Worst GU Toxicity
Grade 1-2	81.8% (72)	74.2% (46)	0.31	77.3% (68)	82.3% (51)	0.73
Grade 3	8.0% (7)	0% (0)	0.04	9.1% (8)	4.8% (3)	0.53
Grade 3^a	–	–		3.4% (3)^b	3.2% (2)^c	1.00
Worst GI Toxicity
Grade 1-2	26.1% (23)	16.1% (10)	0.17	9.1% (8)	9.7% (6)	0.93
Grade 3^a	0% (0)	0% (0)	1.00	1.1 % (1)^d	3.2% (2)^d	0.60
^aAttributed to sRT ^bcystitis, n=2; urethral stricture, n=1 ^ccystitis, n=1; urethral stricture, n=1 ^dproctitis