Radiosurgery for Benign Spinal Lesions

Iris C. Gibbs, M.D.

Associate Professor, Radiation Oncology

Co-Director

Cyberknife Radiosurgery Program

Stanford University

Radiosurgery for Benign Spinal

Lesions

Sean Sachdev, B.S.; Robert L. Dodd, M.D., Ph.D.; Steven D. Chang, M.D.; Scott G. Soltys, M.D.; John

R. Adler, M.D.; Gary Luxton, Ph.D.; Clara Y.H. Choi, M.D., Ph.D.; Laurie Tupper, N.P.

Disclosures



None

Overview



Primary benign spinal tumors



Clinical presentation



Radiosurgery techniques



Indications for radiosurgery



Results

Primary Spinal Tumors

Extradural

Intradural/Extramedullary

Meningiomas

Neurofibromas

Schwannomas

Intramedullary

Astrocytomas

Ependymomas

Hemangioblastomas

52-75% of all primary

spinal tumors

1, 2

1.

Byrne, T. N.; Benzel, E. C.; Waxman, S. G.

Diseases of the spine and spinal cord.

Oxford; New York:

Oxford University Press; 2000.

2.

Gursinghe N.T.

Spinal Cord Tumours

. In Critchley, E. M. R.; Eisen, A., editors.

Spinal cord disease.

Benign Extramedullary Spinal Tumors

characteristic

meningioma

schwannoma

neurofibroma

Age of presentation

5th-7th decade

5th decade

4th decade

Spinal level predominance

Thoracic (80%)

All levels evenly

Cervical (66%)

Multiplicity

1-2%

Rare unless NF-2

associated

Common

Proportion of primary spinal tumors 25%

~33%

3.5%

Gender predominance

Female (75-85%)

None

? Male

Associations

More commonly

psammomatous or

transitional histologies

NF2,

merlin/schwannomin

gene on chromosome 22

NF1,

neurofibromin gene on

chromosome 17

Intradural Extramedullary Tumors

Clinical Presentation:

Local Pain

Radicular Pain

Weakness or motor deficits

Sensory loss

Bladder/Bowel Deficits

40 M with NF2

T10/T12

schwannoma

Anterior Thoracic Meningioma

CHALLENGES:

Thoracic Meningiomas in NF2

CHALLENGES:

CHALLENGES:

Multiple Neurofibromas in NF1

Increasing Use of Spine

Radiosurgery



In recent US survey of

>550 respondents



Spine is 2

nd

most

common SBRT site



57% use 1 fraction



Median dose 18 Gy

Pan et al “A Survey of Stereotactic Body Radiotherapy

Use in the United States”Cancer 2011;117:4566–72

Rationale for SRS to Treat BST

• Most spinal meninigiomas, schwannomas, and

neurofibromas are noninfiltrative and can be

completely resected by experienced surgeons.

• Certain patients however are less than ideal

candidates for standard resection.

– Advanced age

– Medical comorbidities

– Recurrent tumors

– Multiple lesions

– Difficult locations requiring complex operative

approaches

• SRS has an established role in benign intracranial

pathologies.

Spinal Radiosurgery



Indications



surgically difficult location in the spine,



recurrence after prior surgical resection,



medical co-morbidities that preclude surgery



Contraindications



poorly defined margins,



significant spinal cord compression resulting in acute

neurological symptoms, **



tumors which can easily be resected with conventional

surgical techniques. **

Grading Epidural Spinal Cord

Compression

Technical Requirements for

Spinal Radiosurgery



Exquisite Accuracy (submillimeter)



Image-guidance



Stereoscopic kV with tracking

Current Spinal Radiosurgery Devices

System

Immobilization

Image-guidance

Error Analysis

Cyberknife

(Accuray, Inc)

Head mask,

cradle,

vacuum bag

Xsight skeletal

tracking or

Fiducial tracking

Phantom- 0.61± 0.27mm

Patient- 0.49 ± 0.22 mm

Novalis

(BrainLAb,

Inc.)

Head mask,

cradle,

vacuum bag

Orthogonal images

to set-up

Optical tracking

Measure iso dose 2-4%

Patient- 1.36 ± 0.11 mm

TomoTherapy

(Tomotherapy

Inc.)

Head mask,

vacuum bag

CT

Phantom- ± 0.6 -1.2 mm

Patient- ± 4-4.3 mm

Synergy S

(Elekta, Inc.)

BodyFix (Elekta)

Conebeam CT

HexaPOD robotic

couch

Patient (w/o image guidance)-

5.2 ± 2.2 mm

Patient (with image guidance)-

0.9 -1.8 mm (translational)

0.8 – 1.6

o

(rotational)

In-house

systems

Stereotactic body frame

or body cast

CT

Patient- varies from 1-3.6 mm

Adapted from Sahgal et al IJROBP 71(3): 652– 665, 2008

Cyberknife

Synchrony

™

camera

Linear

accelerator

Robotic

Manipulator

Image

detectors

Imaging X-ray sources

Targeting System

Cyberknife™

Robotic Delivery

System

Volumetric Modulated Arc

Therapy

Technical Requirements for

Spinal Radiosurgery



Exquisite Accuracy (submillimeter)



Image-guidance



Stereoscopic kV with tracking



Conebeam



Proper immobilization



evacuated cushion



vacuum body fixation device

Spine SBRT Immobilization

Devices

a) evacuated cushion, b) vacuum body fixation device, c) thermoplastic S-frame mask.

Li et al “Impact of Immobilization on Intrafraction Motion for

Spine Stereotactic Body Radiotherapy Using CBCT”

Technical Requirements for

Spinal Radiosurgery



Exquisite Accuracy (submillimeter)



Image-guidance



Stereoscopic kV with tracking



Conebeam



Proper immobilization



evacuated cushion



vacuum body fixation device



Thermoplastic mask

.

Treatment Delivery Techniques

Target Definition



MRI-CT fusion



Gerszten reported (93% of cases could be adequately

contoured based on fusion)



Challenging cases with instrumentation



CT-myelogram was required



Depending on the system specs



GTV=PTV

Literature for Radiosurgery for Benign Intradural

Spinal Tumors

Series

Menin

g

Schwann

Neurofib

n age

Mea

(yrs)

Tot

al

#pts

Indica

tion

Dose/

# Fx

F/U

Outcome

GERSZTEN

DODD,

1-5 25 96% stable/decreased 3 repeat surgery 1 progression 1 new myelopathy

SAGHAL

2007

(CK)

Marchetti,

Selch

GERSZTEN

Sachdev

Sachdev

(CK)

(CK)

2011

2011

Patient Characteristics

1998-2008

87 Patients with 103 Tumors

LESIONS

Histology (%)

Meningioma

32 (31)

Neurofibroma

24 (23)

Schwannoma

47 (46)

PATIENTS

Age (yr)

Median

53

Range

12-86

Sex, no. (%)

Female

44 (51)

Male

43 (49)

Neurofibromatosis

(%)

Type 1

9 (10)

Type 2

14 (16)

Schwannomatosis

2 (2)

PRESENTING SYMPTOMS

Symptom

Number of lesions (%)

Pain

60 (58)

Sensory Loss

35 (34)

Weakness

30 (29)

Bladder/Bowel Deficits

7 (7)

Asymptomatic

26 (25)

mean follow up of 33 months (range: 6-104)

BENIGN SPINAL TUMORS

Methods/Dosimetry

DOSIMETRY

Average tumor volume, TV (cm

)

5.14 (0.05-54.52)

Average prescribed dose, TD (cGy)

1940 (1400-3000)

Average maximum dose, Dmax (cGy)

2490 (1867-3750)

Median Number of Fractions

2 (1-5)

17.7

19.9

21.1

21.0

25.1

0

5

10

15

20

25

30

35

40

45

50

1

2

3

4

5

Lesio

n

s

Fractions

>50%

Dose Fractionation Details

Clinical Results:

Meningioma

47

28

38

9

25

46

45

9

57

43

--RADIOSURGERY EFFECT ON MENINGIOMA SYMPTOMS

Presenting (%)

Pain

Bladder/Bowl Deficits

Weakness/Motor Deficits

Stable

Overall Symptomatic Response (%)

Pain Response (%)

Improved

Stable

Worsened

Asymptomatic

Sensory Loss

Improved

Worsened

Overall

91%

stable or

improved

with

treatment

Clinical Results:

Schwannoma

57

21

28

4

32

50

36

14

53

29

18

RADIOSURGERY EFFECT ON SCHWANNOMA SYMPTOMS

Presenting (%)

Pain

Bladder/Bowl Deficits

Weakness/Motor Deficits

Stable

Overall Symptomatic Response (%)

Pain Response (%)

Improved

Stable

Worsened

Asymptomatic

Sensory Loss

Improved

Worsened

Overall

86%

stable or

improved

with

treatment

Clinical Results:

Neurofibroma

75

46

42

8

13

17

50

33

11

56

33

RADIOSURGERY EFFECT ON NEUROFIBROMA SYMPTOMS

Presenting (%)

Pain

Bladder/Bowl Deficits

Weakness/Motor Deficits

Stable

Overall Symptomatic Response (%)

Pain Response (%)

Improved

Stable

Worsened

Asymptomatic

Sensory Loss

Improved

Worsened

Overall

poorer

symptomatic

response to

treatment;

67%

Radiographic Results

Stable

Decrease

Increase

47%

53%

--51%

47%

2%*

82%

18%

--

EFFECT OF CYBERKNIFE ON TUMOR SIZE

Histology

Neurofibromas

Meningiomas

Schwannomas

**Usual marked by <10% transient increase in size at 6

months followed by reduction

Recurrent Spinal Schwannoma at T-7

Before

Treatment

24 months

L4 radiation-induced meningioma

A

Pre-treatment

B

Treatment plan

C

38 yr old with NF1

A

B

C

Figure 3: 38 year old man with neurofibromatosis type 1 and multiple innumerable spinal and peripheral

neurofibromas presenting with progressive weakness. (A) the left C2 neurofibroma indicated by the yellow

arrow was targeted for radiosurgery, (B) the radiosurgery plan of 18 Gy in 2 fractions shows the tumor

outlined in red with yellow dots, the thin spinal cord outlined in green, the prescription isodose curve in light

green and the 50 % isodose curve in purple. (C) at 1-year follow-up the tumor was radiographically stable,

although not symptomatically improved

L3-4 Recurrent Schwannoma

72 year old woman with recurrent L3-4 schwannoma, 3 years after resection

A

Pre-treatment

B

21 Gy in 3 fractions

C

Clinical Results:

Post SRS Surgery

Histology

Location

Age

Time after SRS

Tumor Control

Symptoms

Effect of Surgery

Meningioma

T9-10

68

10 months

Stable

Unchanged

No improvement

Neurofibroma

C6

32

13 months

Stable

Unchanged

Better

Neurofibroma

C6-7

52

18 months

Stable

Unchanged

No improvement

Schwannoma

C3-4

37

12 months

Stable

Unchanged

Better

Schwannoma

C2

25

30 months

Stable

Unchanged

Better

Schwannoma

C2-3

71

30 months

Stable

Worse

Better

Clinical Results:

Extended Follow-up

• 21 lesions had follow up > 48 months.

• 1 tumor increased in size

• 3 patients underwent surgical resection for

persistent Sx.

• 2 patients in this group died, one of natural causes

and one after a fall from a ladder.

Stanford series: Complications

• No treatment related mortality

• One case of radiation-induced myelopathy

• One spinal lamina fracture during fiducial

Other complications reported



Transient dysphagia



Dermatitis



Worsening baseline symptoms



Numbness



Pain



motor

Pre

Post

Radiation-Induced Myelopathy

C7-T2 Meningioma after

Radiosurgery

Complication

One patient suffered from transient

radiation induced myelitis 9 months post

treatment

C7-T2 meningioma

7.57cm

3

treated to 24Gy in 3frx

SC: 4.7cm

3

>8Gy, 0.1cm

3

>27Gy

SC Dmax = 29.9 Gy

No previous radiation

Neurologically stable after intervention

(corticosteroids and physical therapy)

Results Summary



Mean follow-up 33 months



Majority of schwannomas and meningiomas stable

to improved symptoms (67 – 100%)



Only ~50% of neurofibromas improved symptoms



98% tumor control (95% 4-yr actuarial control rate)



One late failure observed at 6 years



No treatment related mortality



One transient radiation-induced myelopathy



7 patients had repeat surgery- 6 for worsening

Literature for Radiosurgery for Benign

Intradural Spinal Tumors

Series

Menin

g

Schwann

Neurofib

n age

Mea

(yrs)

Tot

al

#pts

Indica

tion

Dose/

# Fx

F/U

Outcome

GERSZTEN

DODD,

1-5 25 96% stable/decreased 3 repeat surgery 1 progression 1 new myelopathy

SAGHAL

2007

(CK)

Marchetti,

Selch

GERSZTEN

Sachdev

Sachdev

(CK)

(CK)

2011

2011

Lessons learned from these studies



Multiple studies



Good follow-up >3 years



Different platforms



Dose



12-16 Gy in 1 fraction



18-30 Gy in 2-4 fractions (especially for Grade 3 ESCC)



Tumor control



92-100%



Symptom control



>80% for most tumors; more challenging for neurofibroma



UCLA study showed only 12% improved symptoms (?lower

Conclusions

• Image-guided radiosurgery for benign intradural

tumors is feasible and safe.

• The most effective dosing schemes are still being

determined.

• Longer term follow up data is needed to determine

efficacy for such slow growing lesions, however

the presented results suggest tumor growth control

during the study period.