Odds of Getting In
So you've done the course work and received your fancy degrees; now it's time to get to work. Except what you've been working on at school all these years is pretty much all you'll ever be working on, so you probably won't have to go too far.
Many of the universities that offer cancer biology programs also run state-of-the-art cancer research institutes, and they don't want to watch the top talent head off to a rival (yeah, even research institutes can act like high school football teams) (source).
If too much time spent in schools is driving you away from the classroom, pharmaceutical companies and healthcare providers are always looking to expand their team of cancer fighters as well.
Most people have to knock on dozens of doors before landing the right job; if you've done the work and made the connections, those dozens of doors will come knocking on you.
Wait...