Two-year toxicity and PSA dynamics in the initial cohort of the SABR-Dual trial - two-fraction stereotactic radiotherapy for localized prostate cancer using rectal spacing.
case_series · Level IV
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- Record sourced from PubMed, PMID 41876028.
- Also identified by DOI 10.1016/j.radonc.2026.111497.
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Abstract
We present the pre-planned co-secondary endpoint of two-year toxicity and early PSA response in the initial phase-I cohort of the SABR-Dual trial of two-fraction stereotactic radiotherapy (SABR) for localized prostate cancer. 20 patients with favorable intermediate- or low-risk prostate adenocarcinoma received a dose of 27 Gy in two fractions, with an optional integrated boost to 30 Gy. All underwent radiopaque hydrogel spacer and fiducial placement. MRI-based planning and real-time fiducial tracking were applied. Pre-planned secondary endpoints of two-year patient-reported quality of life based on EPIC-26, International Prostate Symptom Score (IPSS), and Sexual Health Inventory for Men (SHIM) questionnaires, toxicity based on CTCAEv5.0 assessment, and temporal PSA dynamics, were analyzed. A median increase in IPSS of 1 (IQR, -1.5-6) occurred at one-year, with a median decrease of 4 (IQR, 0.5-8.5) at two-years. Median SHIM score decreased at one- and two-years by 1 (IQR, -4.5-0.5) and 1 (IQR, -6.5-0.5), respectively. Rates of minimally clinically important change in EPIC-26 subdomains of urinary incontinence, irritative/obstructive, bowel, sexual, and hormonal symptoms decreased between one- and two-years, with the exception of sexual function, with rates of 5/19 (26.3%), 5/19 (26.3%), 6/19 (31.5%), 8/19 (42.1%), and 3/19 (15.8%), at one-year, and 2/19 (10.5%), 3/19 (15.8%), 1/19 (5.3%), 9/20 (47.4%), and 0/19 (0%), at two-years, respectively. Rates of grades 1/2 urinary toxicity at one- and two-years were 30%/30% and 5%/20%, while rates of grades 1/2 bowel toxicity were 0%/10% and 5%/5%, respectively. Mean and median PSA decreased from 5.66 and 5.35 ng/mL at baseline to 1.22 and 0.88 ng/mL and 0.42 and 0.31 ng/mL at 1- and 2-year follow-up, respectively, representing a decrease of 81.3% and 94.8%. Two-fraction prostate SABR using rectal spacing appears safe with acceptable intermediate-term toxicity and excellent PSA response.