I have got 400 and 600 samples in control and test groups respectively. And in each of these two groups, i have an effect variable that occurs at the rate of 30%. this is a retrospective data analysis.

I want to investigate whether the effect variable impairs the patient outcome (response rate as well as median survival) in control and treatment groups and if so, whether such effect is any different in treatment and control groups.

Any ideas which variables i need for this calculation ? What formula can i use to calculate the power for this study. thanks