The overall treatment effect ( tadalafil vs placebo ) for the change from baseline through week 8 in prostate TZ RI was not statistically significant ( least squares mean change : placebo,-0 .01 ; tadalafil , 0.00 ; P = .118 ) , nor was the change from baseline in prostate TZ CPI ( P = .564 ) or CPD ( P = .592 ) .