Together with the hip, metastasis to the spine is the most clinically relevant problem faced by the patient with metastatic bony disease. The obvious implications on disease of the spine would be in relation to paralysis and patients would dread being burdens to their family as a result of fractures there- much like the case with hip fractures. Nevertheless, by a careful selction of procedures and therapeutic options it is often possible to obviate the need for costly therapeutic interventions and optimizing the patients resources and time to match their expectations.
Treatment Considerations for Spinal Metastases Surgery
The main guiding factors in deciding if a patient with metastatic spinal disease would benefit from surgery (Figure 1) falls under the following categories. Often, if a lesser procedure can be done to achieve these ends (alternatives to surgery) then this would be the more desirable option.
About 10% of metastatic bony disease will present without a known primary. It is often necessary to do a biopsy to begin the diagnostic process. Sometimes, when the cell type is obvious (eg. thyroid, kidney, liver) the diagnosis is very accurate. Often however it is a adenocarcinoma which can come from the entire gut or breast. It is usually desirable to obtain a biopsy through a needle inserted through a CT scan but often this is falsely negative. There is therefore sometimes a need to perform open surgery for this biopsy. Therein lies the problem - if an open biopsy is performed often the act of taking out tissue results in instability of the spine and therefore open biopsies are usually accompanied by full decompressions with instrumentations.
The most dreaded of complications of bony metastatic disease, paralysis or impending cord compression is an indication for emergency surgery.
Lost of structures due to destruction by the metastatic deposit is often faced and the dilemma is in choosing to operate to stabilise the patient in a time frame that would be most beneficial for he patient.
Figure 1. This patient had spinal metastatic disease with neurological deficit. The xrays were normal (far left) though the MRI showed obvious invasion of the cord (left). At surgery, we removed the area invading the cord and repaired the dura (covering of the spinal cord). The patient then required screws and rods to be placed to stabilise the spine.
Alternatives to surgery
Every patient with metastatic bone disease needs a multidisciplinary team approach to decide on the most optimal care. This represents a working group comprising the orthopaedic oncologist, medical oncologist, radiation oncologist and palliative care specialist. While many may claim superiority of one modality over the other, in truth it represents the result of multiple disciplines working together. For example, surgery alone without radiation can have a 20% increased failre rate than when surgery is combined with radiation.
This minimally invasive option is ideal for chronic pain syndromes in cancer patients. It also allows histological diagnosis and treatment in specific pathologies (eg. multiple myeloma). It is especially suited to chemotherapy patients in whom multi-level osteoporotic compression fractures occur (Figure 2). Pain relief is similar to vertebroplasty (injection without balloon) but has the added advantage of cement being close to setting at the time of injection (less chance of embolization and extravasation).
Figure 2. We have been trained to use kyphoplasty in the setting of metastatic disease since 2003. Unlike typical uses in osteoporosis , we may have to do multiple levels at a time. It is an ideal procedure to get a biopsy and stabilise the spine and allows the patient to get up quickly.
Philosophy of prophylactic stabilization
In prophylactic surgery, fixation is done before a fracture happens. The indication for surgery was that these “fractures were predictable” (Beals et al 1971). The idea that there should be a reasonable life expectancy before considering surgery is a relatively recent suggestion. Nevertheless, patients with a prolonged life expectancy should receive an appropriately durable reconstruction as opposed to the individual with a short life expectancy for whom an expedient method may be preferable. These indications for surgery based on so-called “projected survival” is more relevant to prophylactic surgery. While for long bones, 6 weeks is a reasonable time, in the spine this time is 12 weeks. In the case of therapeutic fracture management where the fracture has already happened the issues of comfort and nursing take precedence over the "potential" benefits that are proposed for prophylactic surgery.