Methods and results

From 13 electronic bibliographic databases were searched we identified 2,425 potentially relevant articles of which 31 met the inclusion criteria. These were quality appraised. Seventeen studies reported retrospective data, 10 were prospective studies, and three were other study designs. There was one systematic review. There were no randomised controlled trials. There were approximately 7,900 participants in the included studies and 5,782 participants were analysed. The sample sizes ranged from 41 to 859. Cancers reported were: lung alone (n=3); prostate alone (n=6); breast alone (n=7); mixed cancers (n=13); and unclear (n=1). Ninety-three prognostic factors were identified as potentially significant in predicting risk of SCC or collapse. Many of the included studies provided limited information about patient population and selection criteria and they varied in methodological quality, rigour and transparency. Several studies with mixed case populations identified type of cancer (e.g. breast, lung or prostate cancer) as a significant factor in predicting SCC, but determining the risk differential is difficult because of residual bias in studies. Overall the quality of the research was poor. The only predictors identified for SCC were number of spinal metastases, duration of disease, total disease burden and immediate symptomatology of cord involvement.