onc brain

The longer read

The useful content of this document is not the dose recommendation, which simply codifies PACE-B and will surprise nobody, but the two things the panel voted against and the several it could not agree on. Elective pelvic nodal irradiation alongside prostate SBRT drew a unanimous no outside a clinical trial. That is a stronger position than it first appears: whole-pelvis coverage in conventionally fractionated high-risk disease is contested but actively practised, and the panel's line is that the SBRT evidence base offers no footing for extrapolating it. Rectal spacers were similarly rejected at 85%, with the panel acknowledging two randomised trials showing reduced gastrointestinal toxicity in conventional and hypofractionated schedules and declining to recommend the device anyway, on grounds of placement risk, training, and the absence of a large-scale risk-benefit analysis. Reading a consensus document for what it refuses to endorse is usually more informative than reading it for what it endorses, and that is the case here.

The dose question is genuinely open in a way the recommendation section understates. The panel names 36.25 Gy in five fractions as standard, then in the same passage notes that HYPO-RT-PC achieved non-inferiority with a lower biologically effective dose, and that NRG-GU005 in preliminary ASTRO 2025 form reported lower side effects with 36.25 Gy but a slightly higher three-year biochemical relapse rate, cause unexplained. Those two observations point in opposite directions about whether dose is currently set correctly, and the honest read is that the field has settled on a schedule by trial precedent rather than by having identified the therapeutic window. The concurrent trials in focal dose escalation to the imaging-defined GTV and de-escalation to non-suspicious prostate are the ones that will actually answer this, and the recommendation should be read as a floor to build from rather than a resolved question.

The weakest link is high-risk disease. The conclusion states SBRT is increasingly used in high-risk patients, while the evidence section concedes HYPO-RT-PC is the only phase III reporting oncologic outcomes there and high-risk patients made up 11% of it, with PACE-C toxicity published but oncologic outcomes still pending. The panel's own voting reflects this honestly: ISUP 4 and cT3a each drew only 38% support and ISUP 5, cT3b and cT4 drew none. A reader treating high-risk disease with five fractions is therefore working past the panel, not with it, which is worth knowing before quoting an ESTRO consensus in a tumour board.

Urethral sparing deserves scepticism the document does not fully apply. The recommendation to minimise urethral hotspots rests on brachytherapy analogy and a single SBRT association study, while a post hoc PACE-B analysis found no significant association between urinary substructure dose and late urinary toxicity, and the panel flags its own PACE-B-derived V42 <50% constraint as possibly too permissive. Holding all three positions simultaneously is defensible but unstable, and a department investing in urethra delineation workflow should understand it is acting on a plausible mechanism rather than a demonstrated dose-toxicity relationship.

Finally, the structural caveat. Twelve to fourteen voters from nine European countries produce 100% agreement quite easily, and unanimity in a small purposively selected panel measures homogeneity of the panel as much as strength of the evidence. The questions that returned no consensus, prostate volume cut-off, prophylactic medication, and intra-fraction tracking below a 5 mm margin, are the ones where that homogeneity broke down, which makes them the more interesting signals in the document.