Page 26 - Predicting survival in patients with spinal bone metastasesL

CHAPTER II
Risk of bias
Of the 22 included studies, agreement on the overall risk of bias was obtained for 18 (82%). Consensus was reached for the remaining four studies. Inter-observer agreement for the overall risk of bias was substantial (kappa 0.62). Lower levels of agreement were mainly observed in the categories study participation (kappa 0.19) and confounding (kappa -0.13).
Prognostic factors levels of evidence
A total of 43 different prognostic factors were investigated in the 22 included studies. Seven prognostic factors pertained to post-treatment details and four prognostic factors were specific to the received treatment of the patients in the cohort. These prognostic factors were therefore not considered relevant to pre- treatment estimation of survival and were excluded. Fifteen prognostic factors were analyzed only once. As the level of evidence for these factors by definition could not exceed limited they are not mentioned in the results, but are presented in an online supplement. The remaining seventeen prognostic factors are detailed in table 2. Prognostic factors influencing survival in a certain study are mentioned in the column ‘positive association’ and studied prognostic factors not influencing survival are mentioned in the column ‘no association’.
Strong evidence for a positive association with survival was found for the primary tumor, performance status and the American Society of Anesthesiologists (ASA) classification.38 Strong evidence for no association with survival was found for gender, age, number of spinal bone metastases, location of spinal bone metastases, and the presence of a pathologic fracture. The evidence was inconclusive for visceral metastases, neurologic deficit, the interval between diagnosis of the primary tumor and start of treatment for SBM, the presence of extraspinal bone metastases, total number of bone metastases, pain, sphincter function, weight loss and cardiovascular disease.
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