KEY POINTS
- This retrospective multicenter analysis evaluated 117 postprostatectomy salvage radiotherapy plans from five Bavarian university centers. All patients had biochemical recurrence after prostatectomy and received IMRT or VMAT to the prostate bed, with additional boost treatment when local recurrence was present.
- Plans were anonymized and uploaded to the ProKnow cloud platform, where standardized scorecards assessed compliance with SPPORT and RADICALS-HD bladder, rectal and femoral-head constraints.
- Median PTV volume was 213.9 cm³, median PTV D95 64.5 Gy, and median total volume receiving 66 Gy 192.6 cm³. Median bladder and rectal mean doses were 30.8 Gy and 31.7 Gy, respectively.
- For the bladder, 100% of evaluable plans met RADICALS-HD V50 and 92% met V60. Under SPPORT criteria, 89% met V40 and 97% met V65. Constraint failures clustered mainly among patients with smaller bladder volumes.
- Rectal compliance was even higher: 98% met RADICALS-HD V30 and 100% met V40, V50, V60 and V66; 95% met SPPORT V40 and all plans met its high-dose constraint. Every evaluable femoral head met the SPPORT V50 requirement.
- Bladder volume showed a strong inverse relationship with mean bladder dose (r=−0.614) and with bladder V40 (r=−0.615), emphasizing bladder preparation as a major determinant of postoperative dosimetry. By contrast, PTV-related metrics showed only weak correlations with mean bladder dose.
- The analysis measured dosimetric compliance rather than toxicity or cancer outcomes. Institutional contouring, bladder/rectal preparation and planning protocols differed, and SPPORT/RADICALS-HD themselves were not designed to define universal normal-tissue tolerance thresholds.
CLINICAL TAKEAWAY
Modern postprostatectomy salvage RT can meet major trial-derived bladder and rectal constraints very consistently across different centers. The strongest practical message may be simpler than the software: adequate bladder filling appears to matter substantially for bladder sparing, while standardized cloud-based review can expose interinstitutional variation.