Is it really true that cancer can be prevented?

Is it really true that cancer can be prevented? My colleague was recently diagnosed with it and that sort of has scared me a bit.

Yes...Cancer can be prevented in the early stages of patient's life.
A person must stop smoking and maintain a healthy body weight.
He must cut down the alcohol intake as early as possible.
Stop exposing yourself to sun and above all is to eat a healthy diet.

Yes dear cancer can be prevented she is consulting the doc regularly na