Chances of getting cancer? i'm 20. chances of getting cancer or specifically brain cancer? over a lifetime? how to prevent? thanks

Good odds bad diseas: Fortunately Incidence of brain cancer is less than 20 cases per 100,000 population unfortunately most of the brain tumors are malignant. You can't prevent it ( as you did not chose your genes ) Don't worry about it enjoy your life , you will be fine.

Life's dangerous: Assuming you don't have one of the genetic cancer family syndromes, your odds of a primary malignant brain tumor are about 1%. There's nothing you can do to lower the risk. You can read elsewhere about cancer odds; the most important item is for you not to use tobacco, and to keep up surveillance so that if something does pop up, we can manage it. A majority of cancers are cured nowadays.