Movies: does the cancer that joseph gordon-leavitt get in 50/50 exist?

Only a story. It is only a story, some one with 50/50 chance of survival , life and drama around that person , adam lerner character is fiction, possible to have such disease.
Yes. Will reiser, the real-life counterpart, had a neurofibrosarcoma-schwannoma. I'm quite familiar with these and one of my teammates actually had one himself; he also got a cure.