Randomisation took place between June 12 , 2008 , and Feb 1 , 2011.526 ( 57 % ) of 921 randomly assigned patients had received previous docetaxel treatment ( 352 in the radium-223 group and 174 in the placebo group ) and 395 ( 43 % ) had not ( 262 in the radium-223 group and 133 in the placebo group ) .