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search terms used included ‘‘facial nerve schwannoma,’’ ‘‘facial
nerve neuroma,’’ ‘‘radiotherapy,’’ ‘‘stereotactic radiosurgery,’’
‘‘stereotactic radiotherapy,’’ ‘‘radiosurgery,’’ ‘‘radiation therapy,’’
‘‘gamma knife,’’ and ‘‘Cyberknife.’’ In total, 13 articles were iden-
tified that discussed SRS for FNSs. In lieu of repeating the data
from our institutions prior manuscript, we updated our experience
with longer follow-up. Institutional review board approval was
obtained from our institution.
Inclusion criteria for article selection included English language,
treatment of FNS with SRS, follow-up period clearly identified.
Two articles (2,10) were removed that described treatment of
nonvestibular schwannomas with SRS but did not differentiate
outcomes between FNS and other schwannomas (7,8). One article
was included without individual patient follow-up periods iden-
tified (9). However, the overall follow-up period was similar to
the other included studies and thus was kept for analysis. In total,
10 articles were evaluated in addition to our institution data,
yielding 53 patients.
Hearing data were analyzed only when objective measures
were used. Studies that used terms such as ‘‘hearing was stable’’
were not included when the hearing data were not clearly defined.
In our analysis, hearing data were reported using the American
Academy of Otolaryngology (AAO) acoustic neuroma hearing
guidelines (10). FN data were included when the pre-SRS and post-
SRS functional status was reported using the House-Brackmann
(HB) Scale (11).
We defined tumor control as either no change or a decrease in
tumor size. Decrease in tumor size was reported as a separate
category when studies clearly stated their definition. To make
the reporting more uniform, we defined the decrease in tumor
size as either 2 mm in linear direction or 20% volume loss in
accordance with RECIST criteria 1.1 (12). Although it was not
distinctly stated in all of the articles reviewed, all Neurofibro-
matosis II patients were removed from analysis when possible.
RESULTS
Published Data
Our institution’s previous article on this topic was ex-
cluded because we have included updated data for these
patients in this article. This left nine articles that met our
criteria for inclusion for evaluation. When presenting tumor
size, three (33.3%) studies used largest tumor dimension,
five (55.6%) used either three dimensions or tumor volume,
and one (11.1%) did not report tumor size. Three (33.3%)
articles did not report post-SRS hearing data in all patients.
All studies discussed FN outcomes; however, two (22.2%)
used subjective ‘‘improvement’’ or ‘‘worsened’’ statements
rather than the HB score and were not included for FN
outcome analysis. The mean follow-up was 42.1 months
(range, 12
Y
120 mo). All cases in the literature were deter-
mined to be FNS by either involvement of FN segments
other than CPA/IAC on magnetic resonance imaging (MRI)
or based on intraoperative findings when tumor was ini-
tially thought to be an acoustic neuroma.
Treatment Data
Including our institution’s experience, a total of 53 patients
were identified who received SRS for FNS. In looking at
the treatment modalities, 45 (84.9%) patients were treated
with gamma knife (GK), 4 (7.5%) with LINAC, and 4
(7.5%) with fractionated SRS. Meanmargin radiation doses
to the 50% isodose line based on treatment modality were
the following: GK, 12.5 Gy (range, 10
Y
16 Gy); LINAC,
36.3 Gy (range, 12
Y
54 Gy); and all fractionated SRS pa-
tients received 50.0 Gy administered in 25 fractions (2 Gy
per fraction 4 d/wk). There were variable treatment methods
used with LINAC. One patient received one single dose at
12 Gy (13). The other three received fractionated ther-
apy: 2 Gy per fraction 5 days per week for 50 Gy (14), 1.8
Gy per fraction 5 days per week for 54 Gy (15), and 0.5 Gy
5 days per week for 25 Gy (13). There were minimal data
available with regard to cochlear dose.
Tumor Control
Only patients with 2 years or longer follow-up were in-
cluded in the tumor control analysis (n = 45). When defined
as no tumor growth or decreased tumor size, 42(93.3%)
patients had tumor control with SRS and 3(6.7%) did not
(Table 1). According to the guidelines in the Methods sec-
tion, 30 patients were evaluated for growth or reduction in
tumor size. Of these, 15 (50.0%) showed no growth, 2 (6.7%)
showed growth, and 13 (43.3%) were reduced in size after
TABLE 1.
Data extracted from the literature for patients with a minimum of 2-year follow-up
Study
n SRS type
Hearing data in patients with
pretreatment serviceable
hearing (n = 18)
Facial nerve
Tumor control
Follow-up
Unchanged Hearing worsened Unchanged Improved Worsened Yes
No
Current
7 GK 1 (50.0%)
1 (50.0%)
a
6 (85.7%) 0 (0%)
1 (14.3%) 6 (85.7%) 1 (14.3%)
57.1
Ingrosso et al. (14)
1 LINAC n/a
n/a
1 (100%) 0 (0%)
0 (0%)
1 (100%) 0 (0%)
30.2
Kida et al. (16)
14 GK 5 (100%)
0 (0%)
5 (55.5%) 4 (44.4%) 0 (0.0%)
9 (100%) 0 (0%)
31.4
Litre et al (17)
11 GK 2 (66.6%)
a
1 (33.3%)
a
n/a
n/a
n/a
8 (88.9%) 1 (11.1%)
39.5
McCelland et al. (15) 1 LINAC n/a
n/a
0 (0%)
0 (0%)
1 (100%)
1 (100%) 0 (0%)
48.0
Hillman et al. (13)
2 LINAC 0 (0%)
2 (100%)
1 (50%)
1 (50%)
0 (0%)
2 (100%) 0 (0%)
30.0
Madhok et al. (18)
6 GK
n/a
n/a
4 (80.0%) 1 (20.0%) 0 (0%)
5 (100%) 0 (0%)
46.7
Nishioka et al. (19)
4 F-SRS
n/a
n/a
n/a
n/a
n/a
4 (100%) 0 (0%)
67.3
McRackan et al. (4)
1 GK
n/a
n/a
1 (100%) 0 (0%)
0 (0%)
1 (100%) 0 (0%)
62.0
Jacob et al. (9)
6 GK 1 (50.0%)
a
1 (50.0%)
a
4 (66.6%) 0 (0%)
2 (33.3%) 5 (83.3%) 1 (16.7%)
48.0
Total
45
9 (64.3 %)
5 (36.7%)
22 (68.8%) 6 (18.8%) 4 (12.5%) 42 (93.3%) 3 (6.7%)
47.6
a
Studies where the topic of interest was reported for only a portion of the cohort.
F-SRS indicates fractionation SRS; n/a, data not available.
T. R. MCRACKAN ET AL.
Otology & Neurotology, Vol. 36, No. 3, 2015
167