How fatal is kidney cancer (renal cancer)?

Depends on stage of: Disease. Early stage renal cancer has 5 year survival of about 70% and late stage has a 5 year survival of about 10%. See the site below for details. http://www.cancermonthly.com/cancer_basics/kidney.asp.

Stage dependany: Stage is key; stage i very curable, things fall from there, go to nccn.Org for good tables.

Often life limiting.: For kidney cancer that has spread (stage IV), median overall survival is ~ 1 year. In other words, 1/2 of people live longer than 1 year, and 1/2 people live shorter than 1 year. With treatment, median overall survival is now ~ 3 years. In other words, 1/2 of people live longer than 3 years, and 1/2 of people liver shorter than 3 years.