s1042368008000053.pdf

Neurosurg Clin N Am 19 (2008) 379–392

Guiding Patients Through the Choices for Treating

Vestibular Schwannomas: Balancing Options

and Ensuring Informed Consent

Douglas D. Backous, MD, FACS a , * , Huong T. Pham, MD b

a Otology, Neurotology and Skull Base Surgery, Section of Otolaryngology-Head and Neck Surgery,

Virginia Mason Medical Center, 1100 Ninth Avenue, X10-0N, Seattle, WA 98111-0900, USA

Section of Radiation Oncology, Virginia Mason Medical Center, P O. Box 900, Seattle, WA 98111-0900, USA

Counseling patients who are diagnosed with

vestibular schwannomas (VS), formerly known as

acoustic neuromas, can be challenging. These

benign neoplasms, which originate from either

the superior or inferior vestibular nerves, have an

average growth rate of 1 mm 3 per year. Larger tu-

mors can cause brainstem compression with few

noticeable symptoms, whereas smaller VS can

cause vertigo, tinnitus, and hearing loss.

Patients are confronted by the dicult task of

choosing a treatment method based on the advice

of caregivers, currently available literature, and

Internet-based information sources. Patients often

visit the Internet either before or during their

decision period, which can be helpful or even

more confusing for them as they weigh their

options. The health care provider has the re-

sponsibility to explain, in understandable lan-

guage, to the patient or legal representative

governing the patient’s care the proposed treat-

ment options, risks and complications associated

with each form of treatment, and alternatives to

treatment, including no therapy. The medical

record must contain evidence of the patient’s

informed consent, with the exception of emer-

gency situations in which a delay in intervention

could compromise outcomes in a life or limb-

threatening situation. Aside from cases with

brainstem compression and hydrocephalus,

patients should be encouraged to gather informa-

tion before making a treatment decision. For the

physicians managing these patients, information

should be delivered in a balanced way to ensure

patient understanding of their options leading to

adequate informed consent.

Options for treatment include radiation ther-

apy, surgical excision, and observation with serial

MRI. Discerning treatment advantages from

a particular modality is made dicult because of

nonstandardized deﬁnitions of tumor control and

hearing preservation and varied posttreatment

intervals presented in the medical literature.

Surgical techniques and radiotherapy dosage par-

adigms have evolved considerably over the past

two decades. Currently, no randomized, prospec-

tive clinical trial has compared the three treatment

options and there are no clearly accepted, evi-

dence-based, best practices for managing VS.

The treatment of VS requires a multidisciplin-

ary team not only to deliver the chosen therapy

but also to assist in the decision-making process.

At our center, a nurse familiar with VS treatment

coordinates appointments with a neurotologist,

a neurosurgeon, and a radiotherapist. Patients are

encouraged to take the amount of time necessary

to make a decision with full understanding of

potential risks and beneﬁts. The amount of time

necessary to come to a decision depends on the

needs of a particular patient.

This article evaluates the English language

literature, dating back to 1994, to present long-

term results for tumor control and complication

rates for the treatment of VS, excluding cases of

A version of this article originally appeared in

Otolaryngologic Clinics of NA, volume 40, issue 3.

* Corresponding author.

E-mail address: otoddb@vmmc.org (D.D. Backous).

doi:10.1016/j.nec.2008.02.004

neurosurgery.theclinics.com

380

BACKOUS & PHAM

neuroﬁbromatosis type II. The goal is to provide

a guide to otolaryngologists who provide initial

counseling for patients with newly diagnosed VS.

Although the tumor margin doses are similar to

the GK, LINAC radiosurgery typically uses fewer

isocenters and the dose to the tumor is more ho-

mogeneous. Similar to the GK, a non-relocatable

invasive head frame is required for patient immo-

bilization during treatment.

Fractionated stereotactic radiation therapy is

the most recently developed technique for de-

livering high-dose and localized treatment. Unlike

with GK or LINAC, a noninvasive relocatable

head frame or thermoplastic mask is used for

fractionated stereotactic radiation therapy. This

head frame increases patient comfort but may

result in less dose conformality when compared

with other radiosurgery techniques. Subscribers of

this technique believe that fractionation takes

advantage of radiobiologic principles to reduce

late toxicity while maintaining tumor control

[10,11] . The fractionated treatment regimens

range from doses given over several days to stan-

dard fractionation given over 4 to 5 weeks, similar

to the scheme originally used by Wallner.

Data regarding the outcomes GK, LINAC,

and FSRT are reviewed in the next section.

Because few centers in the world oﬀer proton

beam radiation therapy to treat VS, studies that

used proton-based treatments were excluded. All

pertinent papers published from 1994 to the

present that assess local control rates with a me-

dian follow-up of at least 2 years were reported.

Outcomes included tumor control, hearing pres-

ervation, facial neuropathy, and trigeminal neu-

ralgia. In most patients, tumors were sporadic and

had a maximum diameter of %3 cm.

The goal of radiation therapy is to arrest

tumor growth. Local control rate in radiotherapy

studies can be deﬁned as the percentage of tumors

that do not increase in size on follow-up imaging.

Many researchers deﬁne the local control rate as

the percentage of tumors that do not require

salvage therapy. This determination could over-

estimate the control rate because some tumors

may have progressed but are not symptomatic

enough to require further treatment. All three

techniques seem to achieve excellent local control

with a range of 87% to 100% ( Tables 1–3 )

[8,10,12–45] .

Up to 50% of radiated tumors developed

central necrosis that results in transient increase

in tumor volume (23% of cases) [12] . This

phenomenon was observed up to 4 years after

treatment and took from 6 months to 5 years to

disappear. If tumor progression was deﬁned as

tumor growth, then some patients may have

Stereotactic radiation therapy

Radiation therapy was initially used as an

adjunct to surgery in patients with incompletely

resected VS. In a study reported from University

of California San Francisco, Wallner and col-

leagues [1] demonstrated that conventional frac-

tionated radiation therapy to more than 45 Gy

signiﬁcantly reduced regrowth from 46% to 6%

in incompletely resected VS. In this series, 31 pa-

tients treated between 1945 and 1983 were

followed from 2.6 to 40.7 years. The authors

concluded that postoperative radiation therapy

reduced the ‘‘local recurrence rate’’ of VSs that

were incompletely excised or only biopsied and

demonstrated the eﬀectiveness of radiation ther-

apy in the treatment of acoustic neuromas.

Stereotactic radiosurgery, ﬁrst developed in

1951 by Leksell [2] , is a method of delivering

a highly conformal single dose of ionizing

radiation with submillimeter accuracy to an intra-

cranial target. The goal of a single high-dose deliv-

ery was to cause tumor necrosis and control of

growth as an alternative to surgery for patients

who were suboptimal candidates for excision.

The ﬁrst stereotactic radiosurgery treatment for

VS was performed in 1969 with the gamma knife

(GK), also developed by Leksell [3] . The GK is

a highly specialized radiation delivery system

that uses 201 radioactive cobalt 60 sources to de-

liver high-dose radiation accurately to tumor

masses. A stereotactic frame is ﬁxed to the skull

and attached to the treatment table to provide

rigid immobilization of the patient’s head and

ensure accurate localization of the radiation dose.

Thousands of patients have been treated with

the GK. Initially, doses were high, and although

tumor control was excellent, toxicity was signiﬁ-

cant [4–6] . Several reﬁnements, including dose re-

duction, improved target deﬁnition, and treatment

accuracy, have provided excellent tumor control

while minimizing toxicities of treatment [7,8] .

Lower radiation doses were shown to be eﬀective

in controlling tumor growth, whereas tumor

shrinkage could take several years to document

radiographically.

The linear accelerator (LINAC) also can be

adapted to perform stereotactic radiosurgery [9] .

Multiple beam positions or arcs are used to create

a conformal dose distribution around the target.

Table 1

Gamma knife radiosurgery outcomes (median marginal dose 12–14 Gy)

Author (year)

Number

of patients

Local

control rate

Hearing

preservation rate

Facial

neuropathy rate

Trigeminal

neuropathy rate

Other

complications

Flickinger, 2004 [14]

313

98.6% @ 6 y

78%@ 6 y

0% @ 6 y

4.4% @ 6 y

Andrews, 2001 [10]

98%

33%

hc 2.9% vertigo 1.4%

ataxia 1.4%

Massager, 2006 [15]

98%

65%

Ottaviani, 2002 [16]

87%

73%

3% temp

16% mild symptoms

Wackym, 2004 [17]

94%

3% temp

Prasad, 2000 [12]

153

92%

75% for tumors

!1 cc, 57% for

tumors O1cc

2.3%

1.7% perm,

2.5% temp

Chung, 2005 [18]

195

95% @ 7 y

60%

1.4% temp

1.1%

hc 3.5%

Wowra, 2005 [19]

111

95% @ 6 y

2.7%

11.5%

Lundsford, 2005 [8]

829

97% @10 y

78.6%

4.4%

ventriculoperitoneal shunt 0.8%,

tinnitus 0.2%, peritumoral

cyst 3.6%, no radiation-

induced malignancy

Petit, 2001 [20]

96%

88%

4% temp

Hasegawa, 2005 [13]

317

92% @10 y

68%

1% temp

hc 4.1%, malignant

transformation 0.3%

Pollock, 2006 [21]

100%

63%

2.1%

hc 4%

Mysreth, 2005 [22]

103

89.2%

5.2%

hc 3.9%

Paek, 2005 [23]

100%

46%

Litvack, 2003 [24]

134

97.7%

61.7%

2.2% temp

5.8% temp

hc 3.0%

Hirato, 1996 [25]

93%

59%

10.3% temp

3% temp

hc 6.8%

Muacevic, 2004 [26] 219 97% 49% 0.5% 5% temp

Iwai, 2003 [27] 51 96% 56% 0% 4% hc 8%

Kwon, 1998 [28] 88 95% 67% 4% temp, 4% perm 3.4% temp hc 3.5%

Hearing preservation rate is the percentage of patients who maintained or gained useful hearing (Gardner-Robertson class 1-2) after treatment.

Abbreviations: perm, permanent; hc, hydrocephalus; temp, temporary.

382

BACKOUS & PHAM

undergone surgery for salvage treatment unneces-

sarily [13] .

Lundsford and colleagues [8] andHasegawa and

colleagues [13] reported 10-year local control rates

of more than 90% in separate series of patients

treated with GK. The median follow-up period in

Hasegawa’s study was 7.8 years. Partial or com-

plete radiographic response to treatment occurred

in 62% of radiated tumors, and tumors !15 cm 3

had a better progression-free survival than tumors

O15 cm 3 (96% versus 57%, P ! .001). Tumors

not compressing the brainstem or obstructing the

fourth ventricle had a better progression-free

survival (97% versus 74%, P ! .008). Tumor pro-

gression occurred within 3 years from the time of

treatment in most cases. Forster and colleagues

[46] documented local control rates for tumors

O3 cm, 2 to 3 cm, and !2 cm at 33%, 86%, and

89%, respectively. Similar ﬁndings were reported

by Kondziolka and colleagues [4] .

Friedman and colleagues [7] reviewed the

outcomes of 390 patients treated with LINAC

radiosurgery for VS. With a median follow-up

of 40 months and a median dose of 12.5 Gy, the

5- and 10-year local control rates were 90% with

only 1% of patients requiring surgery for treat-

ment failure during the follow-up period. With

a median follow-up period of 48.5 months, Combs

and colleagues [30] also reported a local control

rate of 91% at 10 years.

The longest follow-up periods for the FSRT

studies are from Combs and colleagues [35] ,

Sawamura and colleagues [40] , and Chan and

colleagues [42] . The median follow-up periods in

these studies averaged 48 months, and the 5-year

local control rates in all three studies are more

than 90% (see Table 3 ).

Unlike with use of GK, tumor volume or size

has not been shown to be of prognostic value in

predicting response to treatment with LINAC

radiosurgery or fractionated stereotactic radio-

therapy for acoustic neuromas. Diﬀerent fraction-

ation regimens were used depending on tumor size

[11,37] .

Hearing preservation has not been documented

according to a consistent standard ( Table 4 ), and

no randomized studies regarding tumor control

and hearing preservation have been reported to

date. The use of pure tone audiometry and dis-

crimination testing before and at a standardized

interval after treatment would be optimal. In

most of the radiotherapy papers reviewed, the

statistic that is most often reported is the per-

centage of patients who maintained or gained

Table 3

Fractionated stereotactic radiation therapy outcomes

Author

(year)

Number

of patients Dose

Local

control rate

Hearing

preservation rate

Facial

neuropathy rate

Trigeminal

neuropathy rate

Other

complications

Andrews, 2001 [10]

50 Gy/25 fx

97%

81%

hc 3.6%, vertigo 1.7%,

ataxia 3.6%

Combs, 2005 [35]

106

57.6 Gy/32 fx

93%

98%

2.3%

3.4%

Chung, 2004 [29]

45 Gy/25 fx

100%

57%

4% temp

7% temp

hc 4%

Shirato, 1999 [36]

36–44 Gy/20–22 fx

98%

53%

5% temp

12% temp

Williams/Shokek,

2004 [11,37]

375

25 Gy/5 fx

(!3 cm diam),

30 Gy/10 fx (O3cm

diam), 40 Gy/20 fx

97%

59%

1.5% temp

0.5% perm

1.2% temp

Meijer, 2003 [31]

20–25 Gy/5 fx

94% @ 5 y

61%

Fuss, 2000 [38]

57.6 Gy/32 fx

97.5% @ 5 y 85%

4.8%

Selch, 2004 [39]

54 Gy/30 fx

100%

91.4%

2.8%

3.8%

Tinnitus 5%, hc 0%,

ataxia 2%

Sawamura, 2003 [40] 101

40–50 Gy/20–25 fx

97%

4% temp

14%

hc 11% disequilibrium

16.8%

Poen, 1999 [41]

21 Gy/3 fx/24 h

97%

77%

16%

Chan, 2005 [42]

54 Gy/30 fx

92%

84%

Chang, 2005 [43]

21 Gy/3 fx/24 h

98%

74%

0% perm

Lederman, 1997 [44]

20 Gy/4 fx or

20 Gy/5 fx

100%

93.5% (does not

distinguish useful

from no useful

hearing)

2.6% temp

Ishihara, 2004 [45] 38 15–20.5 Gy/1–3 fx 94% 93% 2.6% temp 2.6%

Hearing preservation rate is the percentage of patients who maintained or gained useful hearing (Gardner-Robertson class 1-2) after treatment.

Abbreviations: fx, fraction; hc, hydrocephalus; perm, permanent; temp, temporary.

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