Considerations for surgical intervention in metastatic cancer to the spine: evaluation of risk factors for pathologic fracture and spinal cord compression, and analysis of pre-operative scoring systems for the prognostication and treatment of patients with spinal metastases

Abstract

The spine has structural load bearing and neural-protective functions, and tumour growth and bony destruction caused by spinal metastases results in pathologic fracture and cord compression, causing pain, neurological deficit, impaired function and quality of life. Surgery is the only method to immediately stabilise the spine and decompress the spinal cord. Survival prognosis is one of the key factors in selecting patients for surgery, and there are a number of scoring systems aimed at prognostication and treatment decision making for patients with spinal metastases, however these differ in the parameters assessed and prognostic value. The ability to predict those patients with spinal metastases most likely to progress to pathological fracture or develop spinal cord compression may simplify the surgical decision-making process and enable earlier surgical intervention, with the potential to prevent permanent neurological deficit and disability and maintain function and quality of life for the remainder of the patient's life.

This thesis considers the complexities of treatment decision making for patients with spinal metastases, with two major aims:

1) An evaluation of patient risk factors and radiological parameters associated with pathological fracture and metastatic epidural spinal cord compression, and

2) Validation of survival prognostication of current pre-operative prognostic scoring systems, in order to optimise the treatment decision-making process.

The methodology involved retrospective assessment of clinical and radiological parameters of 72 patients with spinal metastases who had undergone decompressive and/or stabilisation surgery for pathological fracture and/or metastatic epidural spinal cord compression or nerve root compression.

The items assessed for association with pathological fracture or metastatic epidural spinal cord compression were: tumour size, location, type and lesion morphology, disease burden, pain and function.

Pre-operative scores were calculated for each patient, and the prognostic value of each scoring system evaluated by comparison of predicted and actual survival.

The results showed that tumour size within the vertebral body, vertebral endplate and three-column involvement, tumour growth rate, multiple vertebral metastases, and pain were associated with increased risk for pathological fracture. Vertebral posterior element and costovertebral joint involvement by tumour, primary tumour growth rate and presence of visceral metastases were associated with metastatic epidural spinal cord or nerve root compression.

All patients with pathological fracture had at least one of three risk factors – pain; >25% tumour occupancy of vertebral body; and endplate or 3-column involvement – and incidence of pathological fracture increased with higher number of risk factors.

The Revised Tokuhashi, Bauer, Modified Bauer, and Tomita scoring systems were the most reliable for survival prediction.

It is concluded that these risk factors should be considered in the decision-making process for surgery for spinal metastases. Patients with spinal metastases causing pain, greater than 25% occupancy of the vertebral body and involving the vertebral endplate or all three columns should be considered for prophylactic or therapeutic decompressive and stabilization surgery.

As a component of comprehensive treatment planning, we recommend the use of Revised Tokuhashi, Modified Bauer, and Tomita scoring systems due to their favourable survival prognostic accuracy and clearly outline of treatment strategy according to prognostic group.