The Detection of Metastatic Disease of the Spine in Oncology Patients Using MRI

Skeletal metastatic disease occurs in 20-35 per cent of patients with a malignancy (1,2). Lung, breast, genitourinary and gastro-intestinal tumours account for 80 per cent of primary sites. Breast is the commonest primary in females and prostate the commonest in males. Metastases are usually multiple but solitary deposits occur in approximately 10 per cent. The axial spine is a common site for metastatic disease with up to 52 per cent of metastatic bone disease occurring at this site. Plain radiographs, radionuclide bone imaging and CT of the spine are all part of the investigation of patients with suspected metastatic disease of the spine. All of these techniques have their limitations however. It has been demonstrated that the loss of 50-75 per cent of cancellous bone is necessary for the detection of autopsy proven metastases on the lateral lumbar spine radiograph. Radionuclide bone imaging is highly sensitive, but not very specific for the detection of metastases and has a high false positive rate, particularly in the isolated lesion. Further, false negatives can occur in some malignancies. Thin section axial CT of the spine can be difficult to interpret and the correct level must be selected as CT of the entire spine is very time consuming. Even then