Without treatment for the colon cancer the colon cancer can easily advance to stage 4 colon cancer within 2 to 5 years.
So it's important to get colon screening and colonoscopies starting at age 50 and then continue the colonoscopies every 5 to 10 years depending on how at risk you are at developing colon cancer.
If colon cancer is found during the colonoscopy and you get treated soon afterwards you can usually be cured of the colon cancer before it spreads.
Once colon cancer spreads further and reaches stage 4 then it cannot be cured as easily and may not be able to be cured at all.
So you should get a colonoscopy when needed.