Page 12 - Predicting survival in patients with spinal bone metastasesL

CHAPTER I INTRODUCTION
Due to a rise in the incidence of malignant disease, as well as increased overall survival rates of patients with cancer, the incidence of metastatic disease is on the rise.1-4 Following lung and liver, bone is the third most common site of metastatic spread5 and, depending on the extent and location, can be the cause of pain, pathologic fractures and neurologic deficit, resulting in a reduced quality of life.
Bone metastases are most commonly caused by breast, prostate and lung cancer. Other, less frequently observed primary malignancies are colorectal, kidney and upper-gastrointestinal cancers.6 Depending on the primary tumor causing the bone metastasis, the lesions can have a lytic, sclerotic or mixed appearance. The spinal column is the most frequently affected by bone metastases, followed by the long bones and pelvis.7,8
Several types of spinal metastases are recognized. Intramedullary metastases are located within the spinal cord itself, whereas leptomeningeal metastases are located within the subarachnoid space. These types of spinal metastases are quite rare and are usually seen in end-stage disease. Spinal epidural metastases are located on the outside of the dura mater and the vast majority originates from the osseous parts of the spinal column.
In 90-95% of patients with spinal bone metastases (SBM), pain is the first presenting symptom.9,10 Patients can experience pain either due to fracturing or collapse of the vertebral body, pressure on the periosteum from within the vertebra, or nerve root compression. Neurologic deficit due to SBM mainly presents as sensory or motor deficit through nerve root compression, but in its most severe form, SBM can compromise the spinal cord or cauda equina, leading to paraplegia or cauda syndrome. This occurs approximately in 3% of patients with SBM11 and can be an indication for emergency treatment with either radiotherapy or surgery.
Magnetic Resonance Imaging (MRI) is the modality of choice for demonstrating SBM (figure 1). It is capable of showing osseous metastatic disease, as well as providing essential information on spinal cord and nerve root compression.12-14 Both T1 and T2 weighted images are necessary, preferably in both axial and sagittal planes.15,16 SBM are generally hypo-intense on T1 weighted images and,
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