Eventuellt Carcinom Angels av Norman Spinrad.
At age forty, he is told that he has an advanced, well-spread, and incurable case of cancer, and is given an expected year to live.
He proceeds to do everything probable to cure it, and when that fails, he turns to his specialty: the improbable. He goes to every source, then starts in on the unsourced.
He sets out to explore and conquer his own internal universe. He prepares a potent potion to be inserted by syringe, containing: Novocain; morphine, curare; vlut, a rare Central Asian poison which induced temporary blindness; olfactorcain, a top-secret smell-deadener used by skunk farmers; tympanoline, a drug which temporarily deadened the auditory nerves (used primarily by filibustering senators); a large dose of Benzedrine; lysergic acid; psilocybin; mescaline; peyote extract; seven other highly experimental and most illegal hallucinogens; eye of newt and toe of dog. All of these drugs are meant to induce hallucinations, increase his brainpower, make him go to sleep, and keep him awake at the same time.
He falls into a coma and enters his body as some sort of spirit and cures himself of the cancer, which is personified as a biker gang: the Carcinoma Angels. But his treatment was too effective and now he can't get out.