Every single cancer is a genetic disease. Not necessarily inherited from your parents, but it's genetic changes which cause cancer. So as we sequence the genomes of tumours and compare those to the sequence of patients, we're getting down to the fundamental basis of each individual person's cancer.
Preventative medicine has to be the direction we go in. For example, if colon cancer is detected early - because a person knew he had a genetic risk and was having frequent exams - the surgery is relatively inexpensive and average survival is far greater than 10 years.