In 2011-2012 what is.the estimated percentage of colon cancer awith someone in their 20s how worried should i be?

Very low: If you have no family history of colon cancer, and no symptoms at all, the percentage is extremely low. If any of the above apply, it is a different story.

Extremely low: The incidence of colon cancer is very unusual or even rare under the age of 40. If there is an underlying condition such as colitis or familial polyposis, then the disease can occur very early. If there is a history of a very young person in your family that got colon cancer, then your risk is high enough to have a screening colonoscopy around the same age.

Not worried: The best data i could find was from 2005-2009. The incidence rate for someone 20-24 was 0.5 per 100, 000 people. To give you perspective, the incidence rate for that same age group dying in a car accident is 36 per 100, 000 (2009 data). In other words, you are ~75 times more likely to die in a car accident than even get colon cancer. Colon cancer in the young does happen, it is just a low number.