When should I start screening for colon cancer with a bad family history?

Dear Ask The Doctor: My family on my dad's side runs ramped with colon cancer. We lost our great uncle to it at the age of 65 (I think) and my father is fighting a four year battle with stage 4 colon cancer at the age of 57. His brother was 43 and had a polyp that was just about to go cancerous. My father's doctor in fact said that I should start the screening at 35 because it's a matter of when not if I will get it. So my question is when is too soon to start getting checked? Along with the grim family history I also have IBS which I heard adds to the chances. I am 20 and just after watching my dad go through this and knowing it will eventually get him it just nags at the back of my head "When is it my turn?" So am I over reacting or are my worries justified and I should check before 35 even. I know cancer is hard to get a good idea of over the internet but your best advice would help.

Dear Evin: You indeed have a strong family history of colon cancer. It is recommended to start screening at the age of 50 or 10 years before the earliest diagnosis of cancer in your family. So you may start screening at the age of 34 or 35, since it is highly likely for you to eventually get this cancer.