onc brain

Single-institution retrospective comparison of 693 single-isocenter VMAT SRS plans: HyperArc (23-pt pilot + 350 pts) vs 320 consecutive prior mVMAT pts as historical control. Clinical outcomes evaluated only in the HyperArc cohort.

Plan cohort mixed metastatic and benign/vascular targets; 59.9% single-target, 12.0% with 6 to 22 targets. Clinical cohort: 107 pts with 377 brain mets, median age 58, mostly NSCLC, breast and melanoma.

No margin on GTV. 18-20 Gy in 1 fx, or 30 Gy/5 fx when any target exceeded 2-3 cm or involved deep structures. 10 MV FFF, HD120 MLC, CBCT with 6DOF correction.

Per-target conformity, gradient and falloff indices, mean brain dose, film PSQA against TG-218, planning and delivery times. Clinical: lesion-level LC (no 25% diameter increase) and grade 3+ CTCAE v5 toxicity.

Conformity equivalent; gradient and falloff favor HyperArc; mean brain dose 4.6% vs 5.1%. 1-yr LC 90.1%, 3 grade 3 seizures, no grade 4/5.

Builds on the Clark 2012 class solution and the Thomas 2014 low-dose-spill penalty that matched Gamma Knife plans. Here the automated tool reaches that expert-solution level without nested tuning structures.

Software version differs between eras (Eclipse 15.5 vs 13.6). Planning time measured from structure-set timestamps as a surrogate. LC depends on 47 tumors at risk at 1 year.

The case for automation is standardization, not a dosimetric leap: an expert manual program already sits near the ceiling. What remains unsettled is rotational-error underdosing of off-isocenter targets with zero margin, and which plan-quality metric actually tracks clinical outcome.

Retrospective historical-control dosimetric comparison; clinical outcomes single-arm HyperArc only with 5-mo median imaging f/u and toxicity scored by chart review.

Prospective single-arm trial, N=40, enrolled Feb 2017 to Aug 2019, registered NCT02886572. Median follow-up 15.2 mo. Funded by Varian Medical Systems.

4 to 10 untreated brain mets, age ≥18, KPS ≥70, life expectancy >3 mo, DS-GPA ≥0.5, largest lesion ≤4 cm, >2 mm from optic apparatus; brainstem lesions allowed. Excluded SCLC, germ-cell, lymphoma, leukemia, myeloma, leptomeningeal disease. Median age 61, KPS 90, 6 mets; NSCLC 50%, breast 27.5%; 11 had prior SRS/WBRT.

Single-isocenter VMAT, 1 mm PTV margin. 20 Gy for PTV <2 cm, 18 Gy for 2.0 to <3.0 cm; 5 Gy x5 to all lesions if any PTV >3 cm, any brainstem lesion, or brain V12Gy >20 mL. 24 pts (125 lesions) got 1 fraction, 16 pts (79 lesions) got 5; median beam-on 8 min.

Primary: OS, judged non-inferior if ≥17 of 40 pts outlived DS-GPA-predicted survival. Secondary: local recurrence, distant brain recurrence, neurologic death, AEs, QOL, steroid use.

22 pts outlived prediction; mOS 8.1 mo, 1-yr OS 35.7%. 1-yr local failure 5% (10 of 204 lesions); distant brain recurrence 35.8% at 12 mo. Neurologic death 20% of deaths.

AEs in 73%, all G1-2, mostly headache and fatigue; no G3-5 treatment-related AEs. Radionecrosis in 5 lesions in 4 pts; 2 pts needed surgery. MMSE, Trail Making, HVLT and FACT-Br unchanged at 3 mo.

mOS of 8.1 mo sits inside the range of prior multi-met SRS series summarized in the paper's Table 4 (medians 5.8 to 14.1 mo), most of them retrospective. The randomized SRS vs WBRT trials for 4 to 20 mets (NCT03550391, NCT03075072, NCT01592968) are the comparators this cannot replace.

The DS-GPA benchmark uses the original formulation, measures from first brain-met diagnosis, and was applied here from protocol SRS in a cohort where 11 had prior brain RT. LC and DBF exclude the 8 pts who died before first MRI, and the paper's own Discussion gives a 6-mo distant failure figure (58%) that conflicts with its Results (20%).

The OS endpoint mostly shows the technique does not shorten life against a prognostic index; it cannot show SRS beats WBRT. The more usable signal is the per-lesion one: 5-fraction plans held 98% LC with low necrosis despite larger volumes, which supports hypofractionating high-volume multi-met plans.

Single-arm, N=40, single institution; OS benchmarked against a DS-GPA prediction, not a randomized WBRT or multi-isocenter comparator. Too few events for LC or necrosis modeling.

Retrospective two-center series (Rome, Negrar), 31 consecutive pts, 204 BM. Outcomes by Kaplan-Meier from SRS; dosimetric accuracy from offline CBCT fused to planning CT with residual shifts applied.

Age ≥18, 4-10 BM <3 cm. Median age 60; lung 14, melanoma 8, breast 5. Concurrent systemic therapy in 9 pts (IO 4, targeted 5).

Single-isocenter DCA via Brainlab Elements, 10 noncoplanar arcs at 5 couch positions. 20-22 Gy for <2 cm, 16-18 Gy for ≥2 cm or near critical structures; PTV = GTV + 1 mm (176 lesions) or 2 mm (28).

1y/2y LC 89%/77% per pt, 94%/86% per lesion; mOS 16.1 mo. Coverage loss (V95 <95%) in 28 targets, driven by distance ≥39 mm (P=.0001) and volume <0.40 cm3 (P=.015).

No G3-4 toxicity. Necrosis in 5 (16.1%) pts, 11% per lesion at 12 mo, 2 with G2 motor deficit; individual V12Gy >10 cm3 predicted it (P=.01).

Roper et al showed coverage held at 0.5° simulated rotation but failed in over one-third of plans at 2°; here measured residuals stayed within 0.5 mm / 0.5° tolerance, which is why 1 mm sufficed. Necrosis tracking V12Gy matches the Korytko gamma knife series the authors cite.

The paper reports pt counts inconsistently (4-6/7-10 vs 4-7/8-10; 10 vs 12 pts with coverage loss). LC is not stratified by margin or by distance from isocenter, so the clinical consequence of the dosimetric miss is untested.

The case for 1 mm is a trade-off: the margin rescues small distal targets while Table 4 shows each added millimetre inflates a 1 cm lesion's volume steeply, feeding V12Gy. That trade-off only holds if intrafraction drift is caught and corrected.

Retrospective 31-pt series, median f/u 11 mo, no comparator arm; margin conclusion rests on dosimetric re-computation, not lesion-level clinical failure by margin.