Secondly, the present study was conducted with a limited number of specimens. If we had a sufficient number of patients for this study, perhaps it would have been possible to establish a statistically significant relationship between OS and the expression level of OPN. The present study does not support the results obtained both with in vivo studies and in vitro experiments conducted for this subject matter. Most of the previous studies were carried out with cancer cell lines. These cell lines are thought to be not fully reflecting all characteristics of human cancer cells. The present study is the first study in the literature to show that there is no relationship between OPN and STHMN1 expression and the response to TBR in mCRPC.