3a, b suggestive for spinal metastasis are: bone marrow replacement with decreased signal on T1- and increased signal on T2-weighted images preservation of disc structure on both T1- a
Trang 1Magnetic Resonance Imaging
Today magnetic resonance imaging (MRI) provides the most complete informa-tion for evaluating a vertebral metastatic lesion and therefore it has become the imaging modality of choice [6] MRI is both sensitive and specific and is recom-mended as the initial study in patients with suspected metastatic spinal disease
It clearly provides:
) tumor localization (unifocal vs multifocal) ) extent of bony destruction (sometimes better seen on CT) ) soft tissue involvement
) localization of neural compression (anterior, posterior, foraminal) MRI is the imaging
study of choice
The application of contrast medium is helpful when intrathecal metastasis is sus-pected Repeat MRI studies can demonstrate evolution of the disease process with minimum discomfort to the patient
Characteristic MRI findings ( Fig 3a, b) suggestive for spinal metastasis are: ) bone marrow replacement with decreased signal on T1- and increased signal
on T2-weighted images ) preservation of disc structure on both T1- and T2-weighted images ) spinal cord compression on T1-weighted images
) compression of subarachnoid space on T2-weighted images ) contrast enhancement of the metastatic vertebral body
Figure 3 MRI characteristics of spinal metastases
The predominant findings of spinal metastases are the bone marrow replacement with decreased signal intensity on
aT1W and increased signal onbT2W images, the preservation of disc structure on both T1W and T2W images, the spinal cord compression on T1W images and the compression of subarachnoid space on T2W images.
Trang 2CT Scans
The CT scan is superior only in the assessment of cortical bone and it has
nowa-days been surpassed by MRI [6] It can be of value when extensive spinal
recon-structions are required to improve preoperative planning
Bone Scans
A bone scan should be performed as screening for extraspinal tumor involvement
A radionucleotide bone scan of the skeleton is routinely performed as a
screening to rule out the presence of metastatic disease in the spine and other
areas of the skeleton Bone scanning is very sensitive and may predate
radio-graphic changes of osteolytic or osteoblastic disease by 2 – 18 months [22] It
is not specific to metastatic lesions and will be positive in a variety of benign
processes [30] However, false negative findings can occur with very
aggres-sive rapidly growing metastatic lesions and multiple myeloma [17]
Success-fully treated metastases are inactive and may also produce normal bone scans
[17]
Angiography
Because of the lack of specificity and the occurrence of negative scans, this
imag-ing modality has distinct limitations in evaluatimag-ing the presence of metastatic
dis-ease It provides poor visualization of the bony structures and cannot evaluate
the presence of spinal canal compromise For a conclusive screening of the spine,
bone scanning has been surpassed by MRI
Angiography is helpful
to embolize major feeder vessels in highly vascularized metastasis
Angiography has demonstrated to be also very helpful in evaluating the extent
of the tumor, the localization of major feeder vessels, and in providing a vehicle
for embolization as primary treatment or in association with surgical resection,
e.g highly vascularized renal tumors
Biopsy
A biopsy is a must prior
to treatment
Either open or percutaneous vertebral biopsy can be performed and it is
indi-cated to confirm metastatic disease in a patient with a known primary tumor, to
evaluate a suspicious radiographic lesion, or to provide tissue for hormonal
eval-uation
Always consider a second primary tumor
It is important to consider that the metastasis is not necessarily due to the
known primary tumor but may be a result of a new so far unknown second
pri-mary tumor
Percutaneous biopsy is better performed using a large biopsy needle in order
to obtain a sufficient amount of tissue An anterolateral approach is occasionally
used in the cervical spine while a posterior transpedicular approach is preferred
in the thoracic and lumbar spine The biopsy can be performed under image
CT guidance is preferred for optimal biopsy
intensifier control but CT guidance is preferable because of the more accurate
spatial resolution The accuracy rate for percutaneous bone biopsies is reported
to be 95 % in diagnosing metastatic lesions and the complication rate is as low as
0.2 % [26, 27]
Laboratory Investigation
Routine blood studies are non-specific and often not very helpful in diagnosing
spinal metastases However, for a comprehensive tumor screening the following
investigations are recommended:
Trang 3) complete blood count ) calcium
) phosphorus ) alkaline phosphatase ) urea
) creatinine ) total proteins ) tumor markers Hypercalcemia frequently
occurs in cancer patients
Hypercalcemia, which is frequently observed in cancer patients with metastatic
disease, is thought to be the result of either resorption of bone in osteolytic lesions or tumor secretion of bone resorbing humoral substances Tumors often produce antigens or markers that can be recognized with modern radioimmuno-assays The most frequently used antigens are the carcinoembryonic antigen (CEA) and the prostatic specific antigen (PSA)
Classification
Numerous classifications have been proposed to describe the clinical presenta-tion (pain, neurologic funcpresenta-tion, radiographic changes) and results of treatment for patients with spinal metastases As the treatment of malignant diseases advances and the percentage of patients developing symptomatic metastases increases, there has been a clear need for a better selection of patients requiring
these treatments The most recent scoring systems [12, 19, 20, 23, 33 – 36] not
only take into account the:
) local extension of the spinal lesion but are also based on:
) general health status of the patients ) neurologic conditions
) primary site of the cancer ) number of spinal metastases ) existence of extraspinal bone metastases ) involvement of major internal organ metastases Classification systems
help to guide further
management
According to these classification systems, it is possible to formulate guidelines for the treatment corresponding to patient condition and estimated length of sur-vival
The most recently introduced Tokuhashi scoring system is based on six
parameters to assess the severity of the metastatic spinal disease [33, 34]:
) general condition of the patient (Karnofsky performance status) [23] ) number of extraspinal metastases
) number of vertebral metastases ) metastases to major organs ) primary tumor site (length of survival) ) severity of spinal cord palsy (Faenkel’s grades) Each of the six parameters is graded from 2 (positive) to 0 points (negative per-spective) Their score allows the prediction of a postoperative survival period (< 3 months with 5 points or less, > 12 months with 9 or more points) and there-fore the indication for surgical management for each patient with spinal metasta-sis
Trang 4Non-operative Treatment
The treatment of symptomatic spinal metastases remains controversial The
can-cer patient should not be withheld modern advances in medical care, even if they
are merely palliative The general goals of treatment are (Table 1):
Table 1 General goals of treatment
) relieve pain
) reverse or prevent a neurologic deficit
) restore spinal stability
) correct spinal deformity
) cure the disease (in case of a solitary metastasis)
) improve remaining quality of life
It is important to maintain realistic treatment goals, which are to provide pain
relief and to prevent the complications of the metastatic disease process,
espe-cially neurologic complications Symptomatic spinal metastases can be treated
with various treatment options including:
) hormonal treatment
) chemotherapy
) steroids
) radiation therapy
) surgical interventions
However, for most cases a combination of these options is best suited The choice
of therapy is also based on the general objectives of treatment
A multidisciplinary approach is mandatory
Ideally every patient should benefit from a multidisciplinary team approach
involving oncologists, radiotherapists and spinal surgeons, in order to find the
best management concept and timing
Steroids
Steroids are used initially
in acute neurologic deterioration
In acute neurologic deterioration, the use of steroids has been shown to be
effec-tive in stabilizing and sometimes reversing neurologic dysfunction
Dexametha-sone has been demonstrated to reduce the spinal cord edema and pain associated
with some spinal column tumors Dosage schemes range from a low dose of
dexamethasone (16 mg/day in divided doses) to very high doses (96 mg/day) [7]
The optimal dose which is necessary to treat patients with acute spinal cord
com-pression is somewhat controversial In addition, it is unclear whether high doses
are associated with improved neurologic outcomes when compared to
low-to-Higher dose steroid treatment is not proven
to be better than low-dose treatment
moderate doses High-dose steroids are associated with significantly higher
complication rates such as hyperglycemia, gastrointestinal ulceration and
perfo-ration, and avascular necrosis of the hip In addition, steroids may affect the yield
of biopsy specimens of undiagnosed spinal masses
Radiotherapy
Radiation therapy has become a well-established modality for the treatment of
symptomatic skeletal metastases Significant pain relief has been reported to
occur in 70 – 90 % of patients, probably depending on the etiology of the tumor
[3] When evaluating patients with possible neoplastic cord compression for
radiotherapy, it is important to determine the tumor size and extent, pathological
grade, relative radiosensitivity and whether the source of compression is from
Trang 5the tumor mass or whether it is from bony fragments Favorable indications for radiotherapy are (Table 2):
Table 2 Indications for radiation therapy
) radiosensitive tumor ) neurologic deficit is either stable or slowly progressing ) spinal canal compromise resulting from soft tissue impingement ) multiple myelographic blocks
) no evidence of spinal instability ) systemic condition of the patient precludes surgical consideration ) widespread spinal metastatic disease
) poor prognosis for long-term survival
Radiation therapy is
rou-tinely used in symptomatic
skeletal sensitive metastases
Patients with significant neoplastic bony destruction will often have concomitant pathological vertebral fractures, with retropulsion of vertebral body fragments into the spinal canal that may impinge on the spinal cord Radiotherapy has no chance of relieving the compression in these cases In addition, the bony destruc-tion may result in destabilizadestruc-tion of the spinal column, which may predispose the patient to future neurologic injury These patients are best managed with surgi-cal decompression and stabilization in case their overall medisurgi-cal condition will permit surgery
The standard radiotherapy protocol for palliation of spinal tumors is 300 cGy daily fractions up to a total dose of 3 000 cGy A single posterior field or opposed fields are used to encompass the involved segments plus one to two levels above and below [7] The tolerance of the spinal cord and cauda equina to radiation therapy is the major limiting factor in treatment with higher doses of radiation Higher doses increase the risk of developing radiation-induced myelopathy with resultant loss of spinal cord function
After the decision to proceed with radiotherapy has been made, the timing must be carefully considered Several studies have shown that radiotherapy has deleterious affects on wound and bone healing as well as bone graft incorpora-tion The negative affects of radiation on skin healing have also been well docu-mented The operative incision must be taken into account when developing a radiation treatment plan to prevent potentially disastrous wound dehiscence and
infection However, delayed postoperative therapy (> 21 days) has not been
shown to have this same negative affect and radiotherapy is presently used in combination with surgery in the majority of spinal metastases operated on [3, 10,
16, 38]
Delayed postoperative
radiotherapy is the preferred
treatment
Operative Treatment General Principles
Before recommending a surgical intervention, several factors should be consid-ered The surgeon must determine whether the patient is an appropriate surgical
candidate This consideration should include [3]:
) life expectancy of the patient (at least 3 – 6 months) ) immunologic status
) nutritional status ) tissue conditions (previous radiotherapy) ) pulmonary function should be evaluated and taken into consideration
A formal tumor staging is
required prior to treatment
In this context, a formal tumor staging is required and classification of the spinal
metastasis (e.g Tokuhashi score) is often helpful
Trang 6The general indications for surgery are (Table 3):
Table 3 General indications for surgery
) intractable pain
) progressive neurologic compromise
) spinal instability and deformity
) potentially curable disease
) radioresistant tumors
) failure of radiotherapy
) failure of chemotherapy
) need for open biopsy
General Surgical Techniques
Percutaneous Vertebroplasty
Vertebroplasty is better performed if the posterior vertebral wall is intact
Vertebroplasty was first developed for the treatment of vertebral angiomas and
the indications have been successively extended to osteoporotic vertebral
frac-tures and spinal metastases [14] The procedure is generally performed using
local anesthesia with fluoroscopic or CT guidance From a posterior approach,
the vertebroplasty needle (about 8 – 10 gauge) is introduced through a
transpedi-cular approach to the center of the vertebral body Polymethylmethacrylate or
special vertebroplasty cements are injected under careful radiological control
The goal of the procedure is pain relief (obtained in > 80 % of cases) and the
con-solidation of the vertebra avoiding further collapse Vertebroplasty is performed
in the thoracic and lumbar spine Pathological fractures with an intact posterior
wall are the best indication In experienced hands, the technique can be
per-formed under very careful fluoroscopy control also in cases with some degree of
posterior wall destruction
Decompressive Laminectomy
Laminectomy alone
is rarely indicated
Decompressive laminectomy alone is rarely indicated because metastatic lesions
normally arise from the vertebral body and result in epidural compression that is
either anterior or anterolateral to the thecal sac In these cases, laminectomy is
not effective It produces spinal instability and is reported not to be more
effec-tive than radiotherapy in the improvement of neurologic deficits [21, 37]
However, posterior decompression without instrumentation is indicated in:
) tumors arising from the posterior elements and producing posterior
epidu-ral compression
) patients with multiple vertebral involvements without spinal instability
) rapidly progressive paralysis in very advanced tumor stage (where extensive
spinal procedures would be ill advised)
Prophylactic laminectomy sometimes over several levels can be indicated but
should better be done in conjunction with spinal instrumentation to avoid
fur-ther vertebral collapse
Metastatic tumors involving the upper cervical spine (C1 or C2) are difficult to
address with an anterior approach Due to the wide spinal canal in this particular
area of the spine, they can be treated with decompressive laminectomy,
realign-ment of the spine and posterior segrealign-mental instrurealign-mentation extended to the
occi-put (Case Study 1) [25]
Trang 7Tumor Resection and Spinal Stabilization
In contrast to decompressive laminectomy, the general goals of treatment (Table 1) in metastatic spinal tumors are best accomplished by:
) decompression of neural structures ) debulking (or, if possible, en bloc resection) of the metastasis ) realignment of spinal deformity
) spinal reconstruction/stabilization
However, the feasibility of the various approaches depends on:
) location and extent of neural impingement ) number of vertebrae involved
) region of the spine affected ) need for spinal stabilization ) patient’s medical condition
Specific Surgical Techniques Cervical Spine
Tumors involving a vertebral body between C3 and C7 (possibly T1) can be easily approached with classical anterolateral exposure of the cervical spine [25] For this surgery, the patient is placed prone on the operating table with the cervical spine in extension and mild skull traction Patient intubation may need to be per-formed under endoscopic guidance due to the severe spinal instability Following exposure of the spine, the affected vertebral body and the two adjacent discs are Corpectomy and anterior
column reconstruction is the
therapy of choice for
vertebral body lesions
completely resected to the posterior longitudinal ligament Care is taken always
to work in a posterior-to-anterior direction and never towards the spinal canal The realignment of the cervical spine is easy and mainly occurs spontaneously
after the vertebrectomy is completed The reconstruction of the vertebral body is obtained using bone cement or a special reconstruction cage and spinal fixation with anterior plate and screws is finally performed to produce a solid spinal
sta-bilization (Case Introduction) In the cervical spine, a two or more level involve-ment will require additional posterior instruinvolve-mentation
Tumors involving C1/C2, multilevel cervical metastases, or the cervicothora-cic junction without spinal instability are better addressed from posterior as pre-viously described [25, 29] One or multilevel level laminectomy combined with a plate/rod fixation using lateral mass screws or possibly pedicle screws will pro-vide spinal stabilization (Fig 4)
Metastases at the
craniocer-vical and cervicothoracic
junctions are better treated
from posterior (if possible)
Metastatic tumors involving the upper cervical spine (C1 or C2) are difficult to address with an anterior approach Due to the wide spinal canal in this particular
area of the spine, they can be treated with decompressive laminectomy, realign-ment of the spine and posterior segrealign-mental instrurealign-mentation extended to the
occiput (Case Study 1)
Thoracic Spine
Tumors involving the thoracic spine between T 7 and T12 can be easily
approached through a standard thoracotomy [3, 7, 8, 18, 35] The segmental ves-sels, which course in the vertebral body depressions between the intervertebral Solitary thoracic vertebral
body metastases are best
treated by anterior corpectomy and spinal
reconstruction
discs, are ligated and divided The intervertebral discs are completely resected back to the posterior longitudinal ligament The tumoral mass is progressively removed down to the posterior longitudinal ligaments with rongeurs, curettes
and, if necessary, high-speed drills Following an adequate corpectomy, the
Trang 8pos-a b c d
Figure 4 Treatment of metastasis at the cervicothoracic junction
a,bA 41-year-old lady with a history of breast cancer and multilevel vertebral metastases and cord compression in the
cervicothoracic junction.c,dDecompressive laminectomies and multilevel posterior stabilization with lateral mass
screws in C4 and C5, and pedicle screws from C7 to T6, were performed at surgery.
e
Case Study 1
A 74-year-old man with a history of lung adenocarcinoma presented with disabling upper neck pain resistant to major
pain medication Physical examination revealed adequate general health and a normal neurologic status Radiological
assessment including plain X-rays and MRI showed a pathological fracture of C2 with severe instability and cord
com-pression (a–c) The patient was selected for a posterior approach After careful intubation under endoscopic guidance,
partial spinal alignment was obtained by positioning the patient on the operating table with high skull traction and neck
extension (d) Cord decompression was obtained by laminectomy of C1/C2 and enlargement of the foramen magnum.
Occipitocervical fixation was performed using a screw/rod system from the occiput down to C4 (e–g) The patient died
1½ years after surgery with preserved neurologic conditions and free of neck pain.
Trang 9a b c
Figure 5 Treatment of thoracic vertebral body metastasis
a,bA 74-year-old man with multiple myeloma and T7 pathological fracture with cord compression.cAnterior resection
of the T7 vertebral body and the adjacent discs was carried out before spinal reconstruction with a cage and a screw/rod fixation system.
terior longitudinal ligament typically bulges into the defect created between the intact vertebral bodies It should be removed to allow a complete excision of all the tumor that has infiltrated into the spinal canal The reconstruction of the ver-tebral body is obtained using bone cement or a special reconstruction cage Bone graft is only indicated in cases with a long life expectancy However, bone integra-tion may be a problem in cases with postoperative radiotherapy Spinal stabiliza-tion is completed with an anterior plate and screw system to obtain solid spinal reconstruction (Fig 5)
Metastatic lesions localized in the upper thoracic spine are more difficult to address using an anterior approach A sternotomy is sometimes required and this particular surgery should be performed only in patients with long life expec-tancy [3, 35, 38]
Posterior transpedicular
vertebrectomy is a valid
alternative for tumors in the
entire lumbar and thoracic
spine
The technique of posterior transpedicular vertebrectomy ( Fig 6) has been described as a valid alternative approach for tumors localized in the entire tho-racic and lumbar spine [1, 7, 8, 10, 24] Using this technique, posterior cord decompression is obtained through a large laminectomy extended laterally to the costotransversal joints The surgery is continued by performing the spinal instrumentation before the hemorrhagic phase of tumor resection Pedicle screws are placed in the adjacent vertebrae, usually one level above and one below The procedure is followed by the complete resection of both pedicles using drill, curettes and pituitary rongeurs until exposure of both nerve roots Follow-ing the pedicle structures, in an oblique inwards direction, a cavity is created in the vertebral body by piecemeal tumor resection The vertebrectomy is progres-sively carried out as an eggshell procedure, taking care to leave the vertebral body cortex intact and avoid any injury with the anterior located segmental ves-sels Using the same access and passing above and below the nerve root, the adja-cent discs are also resected The vertebrectomy is completed by ventrally pushing and resecting the tissues left along the posterior longitudinal ligament Care must be taken not to push against the cord The reconstruction of the anterior column is obtained using methylmethacrylate pushed into the defect with a large
Trang 10a b
Figure 6 Single-stage posterior transpedicular vertebrectomy and circumferential reconstruction
aFor metastatic compressive fractures of the thoracic and lumbar spine in a patient with fair general health and/or
multi-ple metastases, an accepted approach is a vertebrectomy and reconstruction through a single-stage posterior
transpedi-cular approach.bPedicle screw instrumentation of the vertebrae above and below is first performed The posterior
decompression includes complete laminectomy, cord decompression, facet joint resection and pedicle removal on both
sides Careful piecemeal vertebrectomy and resection of the two discs is performed from posterior using curettes and
pituitary rongeurs.cAt this point, the previously inserted instrumentation is used to realign the spine.dThe vertebral
body is reconstructed using bone cement, which can be finally compressed by the instrumentation in order to obtain
solid fixation.
syringe The definitive posterior instrumentation is then completed connecting
the previously inserted pedicle screws with two lateral rods (Case Study 2) This
technique may be less effective in the radical resection of the metastatic lesion
but has been described as less invasive for the patient who does not require
post-operative ICU recovery and can be immediately mobilized without external