Of the deaths , 63 in the surgery group and 99 in the watchful-waiting group were due to prostate cancer ; the relative risk was 0.56 ( 95 % confidence interval [ CI ] , 0.41 to 0.77 ; P = 0.001 ) , and the absolute difference was 11.0 percentage points ( 95 % CI , 4.5 to 17.5 ) .