Cabrini Hospital, Malvern and
Austin Hospital, Heidelberg, Vic
The role and value of surgery in vertebral column metastatic disease is still poorly understood. In the opinion of the author this precludes a number of patients from being offered an appropriate surgical option as part of an individualised management strategy.
Until recently, only one study was available in the literature comparing the outcome of a surgical procedure (laminectomy only) followed by radiotherapy, to radiotherapy alone for epidural metastases.1 It is over 20 years since its publication. A comprehensive review of the literature relating to the evidence for surgical intervention in spinal metastatic disease recently has been published.2 The conclusion of the authors was that no guidelines could be provided in relation to surgical management due to insufficient evidence; they did however produce their own recommendations.
The predilection of certain tumours for bone (especially the spinal column) is well documented in clinical and autopsy studies3-6 and therefore with an ageing population the expectation would be for an increased incidence of patients presenting with symptomatic metastases.
Apart from direct surgical intervention, in selected cases there may be a role for vertebroplasty and kyphoplasty which would be carried out by specialist interventional radiologists. The place of these interventions in the treatment of metastatic spinal disease is yet to be determined.
It must be made clear to the patient and relatives that surgical intervention for symptomatic spinal lesions is not curative; there is currently no data to support the proposition that it will improve survival duration. Surgery can be a powerful palliative tool aiming to improve quality of life;7 it can do this by providing pain relief and maintaining or restoring neurological function. Patients presenting with paraplegia of greater than 24 hours duration have very low rates of neurological salvage.7
Recently, a study has been published in abstract form that looked at 101 patients with malignant spinal cord compression due to solid tumour metastasis.8 The patients had only a single site of cord compression, and were randomised to surgery (within 24 hours) and radiotherapy or radiotherapy alone. Sixteen patients in each group were unable to walk at study entry. Fifty-six percent of patients in the surgical group recovered their ability to walk, while only 19% in the radiotherapy group achieved the same level of function (p=0.03). Overall, the surgical group retained their walking ability significantly longer (median 126 days vs 35 days, p=0.006). Morphine and dexamethasone use was significantly reduced in those receiving surgery. While survival was not significantly different, there was a trend to longer survival in those receiving surgery.
Spinal pain can be produced by tumour invasion of the spinal column (with or without collapse of a vertebral body), deformity developing secondary to tumour-induced instability and epidural compression (with or without neurological involvement).
Radiotherapy has an initial role when vertebral body height is preserved and the tumour is radiosensitive. Radiotherapy has no role when there is spinal column deformity causing pain or neurological dysfunction, or when bony fragments as opposed to epidural (soft) tissue cause neural compression (spinal cord, cauda equina or nerve root). Surgery can be offered when radiotherapy fails, however, the rate of neurological salvage declines and surgical morbidity increases (particularly wound infection rates) in a previously irradiated field.9,10
This is one of the most difficult and crucial components of management. It is generally agreed that the anticipated minimum length of survival should be three months.11 Beyond this there are numerous variables that are considered by the surgeon making the assessment. The factors that require consideration include the patient’s systemic condition (nutritional and functional status), the sites of other non-spinal metastases and the impact of chemotherapy and prior irradiation on immunologic function.
MRI is undoubtedly the diagnostic procedure of choice, and can assess for compression at multiple sites.
Surgery can be offered to an appropriate range of candidates whose load of spinal disease may range from a solitary lesion to extensive non-contiguous disease.
The gamut of surgical procedures that can be offered to patients is not limited to laminectomy. There is now an extensive range of mechanical devices employed in surgical procedures that provide immediate stability to the affected spinal column. This can have the affect of immediate pain reduction and allow rapid post-operative mobilisation. The spinal column from the cranio-cervical junction to the sacrum can be accessed. The surgical procedures carried out may include decompression alone or a combination of decompression, reconstruction and stabilisation. The surgeon assessing the patient should have expertise in complex spinal surgery.
In the thoracic spine anterior pathology at the cervico-thoracic junction or in the upper thoracic region (T1-T3) can be approached via a ‘modified anterior approach’ which requires resection of the medial third of the clavicle and the sterno-clavicular joint.
From T4-T12 a thoracotomy (trans-thoracic approach) provides the best access (figure three).
Posterior approaches in the thoracic spine will usually involve removal of the lamina and on occasions the pedicle to facilitate spinal cord decompression. In select patients who have severe circumferential cord compression anterior and posterior approaches may be combined (figure four).
Pathology in the lumbar region is usually approached from the posterior direction; if anterior access is required for decompression of the conus or cauda-equina this is usually via a retro-peritoneal route (figure five).
The most common post-operative complication in the majority of surgical series for spinal tumours is wound infection. There is a statistically significant difference in wound infection rates and other major and minor complications in patients who had pre-surgical irradiation and those who did not.7 Nutritionally-depleted patients undergoing any surgical procedure are known to have a higher risk of infection. There does not appear to be any correlation between preoperative haemoglobin, white cell, lymphocyte and platelet counts and surgical morbidity. Early mobilisation post surgery is important to minimise the risk of pneumonia and deep venous thrombosis; the advent of a variety of internal fixation devices makes this possible and safer.
Patients with spinal cord compression caused by bone instability and/or collapse or progressive neurological deterioration who are being considered for surgical intervention should avoid preoperative radiotherapy. The decision to proceed to surgical intervention can be made only after multiple factors, which importantly include the wishes of the patient, are considered.
8 Regine WF, et al. Metastatic spinal cord compression: a randomized trial of direct decompressive surgical resection plus radiotherapy vs. radiotherapy alone. Int J Radiat Oncol Biol Phys. 2003;57(Suppl 2):S125.
9 Bridwell KH, et al. Posterior segment spinal instrumentation (PSSI) with posterolateral decompression and debulking for metastatic thoracic and lumbar spine disease: Limitations of the technique. Spine 13, 1988, p1383-94.