CNS
One retrospective GKRS vs LINAC comparison for vestibular schwannoma SRS, median f/u 27 mo: too short and underpowered to separate the platforms on late cranial nerve toxicity.
Gamma Knife vs LINAC-based radiosurgery for vestibular schwannoma (retrospective review)
ForVestibular schwannoma, mostly Koos II solid, intracanalicular or mixed
TL;DRLocal control 98.8%; no difference in new vertigo, gait disturbance or facial palsy with GKRS (n=36) vs LINAC (n=49) SRS for vestibular schwannoma.
The 98.8% local control is freedom from further VS-directed intervention; volumetric enlargement still occurred in 6/36 GKRS and 9/49 LINAC pts. The LINAC arm pools margin-free 12 Gy to the 80-99% IDL with post-May 2017 frameless 12 Gy plus a 5 mm PTV margin, era split unreported, so it cannot say which LINAC approach matches GK.
In small, mostly Koos II vestibular schwannoma, this supports GK or LINAC single-fraction SRS chosen by local availability when weighing new vertigo, gait disturbance or facial palsy; it does not inform hearing preservation, which the series did not report.
The 98.8% local control is freedom from further VS-directed intervention; volumetric enlargement still occurred in 6/36 GKRS and 9/49 LINAC pts. The LINAC arm pools margin-free 12 Gy to the 80-99% IDL with post-May 2017 frameless 12 Gy plus a 5 mm PTV margin, era split unreported, so it cannot say which LINAC approach matches GK.
9 details
Retrospective chart review across multiple sites of a single institution, VS treated 2008-2017; N=85 (36 GKRS, 49 LINAC). Platform set by provider preference, as GKRS and LINAC sit at different centers. Median follow-up 27 mo.
Vestibular schwannoma, 95.3% solid, intracanalicular (45.9%) or intra- plus extracanalicular (43.5%); Koos II majority with no Koos difference between cohorts (p=0.65). Pre-SRS symptoms were common: tinnitus 62.4%, gait disturbance 48.2%, vertigo 30.6%.
All single-fraction SRS. GKRS: 12.5 Gy to the 50% IDL, stereotactic head frame. LINAC: 12 Gy to the 80-99% IDL with no CTV/PTV margin, then from May 2017 frameless, 12 Gy to the 100% IDL with a 5 mm PTV margin by VMAT.
No primary endpoint stated in source. Outcomes were new tinnitus, vertigo, gait disturbance and facial palsy (HB grade 3 or higher) in pts free of each at baseline, plus volumetric MRI tumor control. Hearing not reported; trigeminal dysfunction excluded for inconsistent documentation.
Local control 98.8%, with 1/85 pts needing salvage (surgery, LINAC arm). No difference in direction of tumor size change (p=0.199).
| New symptom | GKRS | LINAC | p |
|---|---|---|---|
| Tinnitus | 1/13 (7.7%) | 1/19 (5.5%) | 0.0007 (MVA) |
| Vertigo | 1/28 (3.6%) | 2/31 (6.5%) | 0.785 |
| Gait disturbance | 4/18 (22.3%) | 4/26 (15.4%) | 1.000 |
| Facial palsy (HB ≥3) | 0/34 (0.0%) | 2/48 (4.2%) | 0.509 |
| Tumor outcome | GKRS (n=36) | LINAC (n=49) |
|---|---|---|
| Decreased or stable | 30/36 | 40/49 (81.6%) |
| Increased size | 6/36 (16.7%) | 9/49 (18.4%) |
| Salvage required | None | 1/49 (2.0%) |
Both new LINAC facial palsies resolved (2/2); none occurred after GKRS. New gait disturbance resolved in 3/4 GKRS and 2/4 LINAC pts, and the single new GKRS tinnitus persisted.
Authors position this against prior series reporting favorable local control with GKRS or LINAC individually, where direct symptom and QOL comparisons were lacking. The source names no randomized GK vs LINAC comparison; the authors call for prospective data.
The 'QOL' outcomes are chart-abstracted symptoms, with HB grade assigned by the reviewing author when not documented. Mean follow-up differs (24 vs 36 mo), and the tinnitus p=0.0007 on multivariable analysis rests on 1 event per arm. Methods and results disagree on pre-2017 LINAC immobilization.
Median follow-up of 27 mo sits inside the 3-year window in which the authors cite 20-30% pseudoprogression, so the enlargements in both arms are not yet resolved as benign. The data show no signal of platform-specific vestibular or facial harm; they do not show parity.
Retrospective, provider-preference allocation, N=85; symptom comparisons use difference tests on single-digit event counts, so the 'interchangeable' conclusion is not something this design can establish.
- Does hearing preservation differ between GK and LINAC SRS?
- Does a 5 mm PTV margin on frameless LINAC add cranial nerve toxicity?
- Tumor control beyond the 3-year pseudoprogression window