not an oncologist, but there are only so many nucleotides in that gene. yes all cancer is personal but they all have similarities. p53 for example, is often inactivated; it is the gene that makes cancer cells suicide. no single mutation causes cancer, it is a combinations of them. in short, our DNA gets mutated daily no matter what we do and if we live long enough cancer will kill us, but some regions are more susceptible and other have no effect (called silent mutations)