Calculating Sample Size for survival analysis

[#1]

Hi,

I'm trying to calculate a sample size for survival analysis in Oncology. If I assume a constant hazard ratio and I have an estimate of overall survival (OS) and if I'm assuming that I need, say 80% power, how do I calcualate sample size in SAS JMP? 

Any ideas?

Thanks,

Rakhi 

[#2]

Rakhi,

Can you provide a few more details? Are you comparing treatments? How many? Are their other factors that you're comparing or are you stratifying your subjects?  

Thanks, Don