Page 28 - Predicting survival in patients with spinal bone metastasesL

CHAPTER II
Even though the eligibility criteria for this study were strict, several limitations were observed. Firstly, 68% of the included studies were conducted retrospectively and 55% of the studies consisted of populations that were treated either only with surgery or only with radiotherapy. This increased the risk of bias and therefore the quality of our results. Also, the way the studies evaluated the prognostic factors was heterogeneous and several different cut-off points were used.
The primary tumor was investigated as a potential prognostic factor in all but one study. Even though several different classifications were used, it was found to be associated with survival in 86% of the included studies, leaving no doubt that an accurate primary tumor classification is required for prognostication in patients with spinal bone metastases. The same applies to the performance status, with a positive association rate of 93%. Irrespective of which specific score is used, it provides essential information for accurate prognostication. The ASA classification was investigated in two studies with a low risk of bias and both found a positive association with survival. Because it is rather similar to the performance status, it remains to be seen whether there is a significant benefit to including both factors in a prognostic model.
Age was found not to be associated with survival in 80% of the included studies. Considering the fact that a performance score generally provides a much better measure of a patient's health – and therefore prognosis – than age does, it is not unexpected that this variable is not significantly associated with survival in a multivariate analysis. Gender also was not associated with survival, with a rate of 79%. Breast and prostate cancer make up a large percentage of the populations in the included studies. Since they are gender specific, it is not unlikely that any potential effect of gender is corrected on multivariate analysis. Gender might play a role in SBM prognostication for certain primary cancers with a more even distribution, such as lung cancer. Number and location of the SBM, as well as the presence of pathologic fractures, had no effect on survival in the majority of the included studies. Even though these factors are important to consider when deciding on treatment – for instance determining extent of radiation field or levels of surgical fixation – they most likely do not need to be considered with respect to survival.
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