onc brain

The longer read

The core of this guideline is a reweighting of the WBRT question around neurocognition rather than survival. Its anchor is a set of five RCTs of local therapy with or without WBRT, all in 1 to 3 brain mets (one allowing 4), in which adding WBRT improved intracranial control without improving survival, with N0574 showing worse neurocognitive deterioration and QoL from the combination. That evidence is consistent and long-standing, which is why SRS for up to 4 intact mets carries the only Strong/High grade in KQ1. Nothing here challenges it; the guideline codifies a decade of drift away from WBRT.

The more consequential content sits in the rows with weaker grading. Extending SRS to 5-10 intact mets rests on JLGK0901, a prospective observational study comparing count strata within an SRS-treated cohort, not a randomized comparison against WBRT, plus retrospective survival data. The panel was disciplined about the boundary: it declined to extend the recommendation to 11 to 15 mets because only 10 pts in the supporting retrospective series fell in that band, and it flagged a Japanese series suggesting the worse survival seen with 5 to 15 mets might be driven by the highest-count subgroup. The conditional grade is honest. A reader treating a pt in the 5-10 band with SRS is inside the guideline but on a Low-quality evidence base, and the randomized answer, NCT01592968 comparing SRS with WBRT in 5 to 15 mets, was not available to the panel.

The dose-fractionation grid deserves the most skepticism from an RT reader. The guideline itself states that no randomized or prospective controlled study has compared clinical outcomes by SRS dose and fractionation. The size thresholds descend from RTOG 90-05, a phase 1 MTD study in pts previously treated with focal RT or WBRT, and the multifraction preference above 2 cm comes from retrospective series and a BED10 ≥5000 cGy association. These are sensible defaults rather than tested thresholds, and a lesion straddling a size cut next to the brainstem or optic apparatus remains a judgment call the grid does not resolve.

The systemic-therapy recommendations are expert-driven by necessity. There is no randomized evidence on upfront vs deferred RT for pts starting immunotherapy or CNS-active targeted agents, and the response data the panel cites come from trials that mostly excluded symptomatic or steroid-requiring pts and enrolled small-volume disease. Recommending upfront local therapy for symptomatic mets follows from that exclusion, not from a head-to-head result, and the deferral option for asymptomatic pts is appropriately conditional on surveillance access and salvage capacity.

What would make parts of this wrong: if CCTG CE.7 or the DFCI trial shows HA-WBRT plus memantine is neurocognitively comparable to SRS in higher-count disease, the 5-10 SRS row weakens. If prospective deferral data show early progression approaching the up-to-40% rate the panel cites, the asymptomatic deferral window narrows. The Sept 2020 literature cutoff means the guideline predates several trials it names as pending, and its own commitment to replacement or reaffirmation within 5 years of publication is the clock to watch.