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integrity.
6
It has even been argued that primary micro-
surgery with gross total resection (GTR) is the preferred
treatment altogether for VS to avoid the challenges and
potential morbidity of surgery following radiation.
8
In
this study, we report our experience treating a series of
patients with VSs that failed primary SRS and under-
went microsurgery for salvage.
MATERIALS AND METHODS
Study Design
Prospectively maintained VS clinical databases at two sep-
arate institutions were queried, and all patients who underwent
salvage surgery between 2003 and 2015 for recurrent sporadic
VS after primary radiation failure were identified. Patients with
neurofibromatosis type 2 (NF2) were excluded. Matched controls
were identified from the same clinical databases, including sub-
jects who underwent primary microsurgery for treatment of spo-
radic VS. Match criteria included patient age (within 5 years),
tumor size (within 5 mm), and treatment center. Demographic,
baseline clinical, and treatment outcome data were collected.
Tumor size and hearing class were reported according to the
American Academy of Otolaryngology–Head and Neck Surgery
guidelines for VS outcomes.
10
Facial nerve function was scored
according to the House-Brackmann (HB) grading scale.
11
Cystic
VS was defined as a tumor with a predominant cystic appear-
ance. Growth was defined as greater than 2-mm increase in lin-
ear dimension on serial imaging. Great care was taken to avoid
misinterpreting postradiation tumor swelling, typically seen on
the initial 6-month follow-up magnetic resonance imaging (MRI)
scan, as tumor growth.
12
Serial post-SRS imaging was available
in 36 of 38 (95%) cases, whereas two patients had only one post-
SRS scan prior to salvage surgery. The authors define GTR when
all microscopic disease has been removed; near total resection
(NTR) is specified when less a 5
3
5
3
2-mm pad of adherent
tumor is intentionally left on the facial nerve, brainstem, or vas-
culature to preserve neurological integrity; and subtotal removal
is specified when anything less than near total resection is per-
formed.
13
Following SRS, serial MRI scans are generally obtained
every 6 months for the first year, then annually for the next 2
years and biennially thereafter. Following microsurgical resection
of VS, postoperative clinical and radiographic (MRI) follow-up
was performed at 3 months and at a minimum of every 2 years
thereafter. More frequent follow-up was performed when clini-
cally indicated if less than GTR was performed.
Primary outcome measures included facial nerve function
and tumor control following salvage surgery. Descriptive statis-
tics were used to describe demographic and clinical data. Wil-
coxon rank-sum and Fisher’s exact tests were used to compare
continuous and categorical variables as appropriate. Logistic
regression modeling was performed to identify independent var-
iables associated with good (HB grade I–II) postoperative facial
nerve outcome after adjusting for age, tumor size, extent of
resection, and duration of follow-up. Research approval was
obtained from the institutional review board (IRB 13-009442)
and the regional ethical committee (NSD 13199) at each partici-
pating institution, respectively, prior to study commencement.
Data were analyzed using JMP 10 Statistical Discovery Soft-
ware (S.A.S. Institute Inc., Cary, NC).
P
values
<
0.05 were
considered statistically significant.
RESULTS
Primary Radiation Therapy
Thirty-seven patients underwent salvage surgery for
radiation treatment failure between 2003 and 2015 (Fig
1). Indications for initial tumor radiation included docu-
mented tumor growth (35, 95%) or patient preference (2,
5%). Fifty-one percent of patients were female, and the
median age at time of primary SRS was 57 years (range
30–80 years). At the time of primary presentation, all
patients had normal facial nerve function, and pretreat-
ment hearing class was documented in 35 cases: 15
(43%) were class A; two (6%) were class B; two (6%) were
class C; and 16 (46%) were class D. Other primary pre-
senting symptoms included imbalance (6, 16%) and tri-
geminal neuropathy (3, 8%). The median tumor size was
1.5 cm (range 0.5–2.9 cm) and 24 (65%) were right-sided.
Four (11%) VSs were confined to the internal auditory
canal, two (5%) were cystic, and none presented with
brainstem edema. The original tumor size was unknown
or missing from the medical record for three patients
who initially received radiation treatment elsewhere.
Table I summarizes treatment characteristics of the
37 subjects who received primary radiation therapy.
Thirty-three patients (89%) from this group were treated
at the authors’ institutions, whereas four were referred
from outside centers after diagnosis of tumor growth fol-
lowing prior radiation. Following radiation, three (8%)
Fig. 1. Serial axial T1-weighted MRI with gadolinium (A) demonstrating a right-sided vestibular schwannoma with 0.5 cm of cisternal exten-
sion that was treated with primary stereotactic radiosurgery. (B) Following radiation, the tumor demonstrated progressive growth to a size
of 1.2 cm over the course of 3.4 years. (C) The patient subsequently underwent translabyrinthine craniotomy with gross total resection and
has no evidence of residual progressive disease with over 2 years of follow-up.
Wise et al.: Surgical Salvage for Recurrent VS
184