KEY POINTS
- This multi-institutional retrospective study included 74 prostate cancer patients treated with 5-fraction SBRT using CT-guided online adaptive radiotherapy between January 2023 and June 2024.
- The prescribed dose ranged from 36.25 Gy to 38 Gy in 5 fractions; 4 patients received a 40 Gy simultaneous integrated boost to an intraprostatic lesion.
- The adapted plan was selected in 352 of 370 fractions (95%), and 60 of 74 patients (81%) had all 5 fractions adapted.
- Mean adaptive planning time was 18.7 ± 4.8 minutes; the daily contoured CTV was within 5 cc of the simulation volume in 90% of fractions and within 5% in 68%.
- Adaptation improved at least 1 clinically meaningful DVH metric in 85% of fractions; PTV V98% >95% was achieved in 99% of adapted plans versus 67% of scheduled plans, and rectum V35Gy <3 cc violations decreased from 5% to 0%.
CLINICAL TAKEAWAY
CT-guided online adaptive prostate SBRT appears feasible across two centers, with manageable treatment times and frequent dosimetric gains in target coverage and rectal sparing. The first-fraction benefit, treated seminal vesicle length, and body mass index may help identify who benefits most from adaptation. But the study did not collect patient- or clinician-reported toxicity, so this is technically relevant workflow evidence, not proof of clinical benefit.