Since actor-coproducer Seth Rogen helped to bring "Superbad" to life, "50/50" might also suggest a sex comedy, except Jonathan Levine's film is more like a drama with comedy sequences (some of which involve sex). In a switch from his "Inception" smoothie, Joseph Gordon-Levitt plays Adam, a strait-laced 27-year-old who works in Seattle public radio with his hedonistic best friend, Rogen's Kyle. Back pain brings Adam to an oncologist who diagnoses cancer, prescribes chemotherapy, and recommends counseling, which leads him to Katie, a doctoral student (Anna Kendrick) who makes up in compassion what she lacks in experience. If Kyle takes the news with good humor, Adam's girlfriend, Rachael (Kendrick's "Twilight" costar Bryce Dallas Howard), puts on a strained smile, while his mother (Anjelica Huston) goes into freak-out mode. At the hospital, Adam also befriends two cancer patients (Philip Baker Hall and Matt Frewer) who share their foul-mouthed wisdom--along with marijuana-laced macaroons--but Rachael finally cracks, leaving Adam to fend for himself, except that he isn't as defenseless as he thought, which comes in handy when he finds out the chemo isn't working. Will Reiser, who wrote the script, drew from his own experience, and the results ring true, even if he's too hard on Rachael, who sincerely tries to be supportive. In his follow-up to "The Wackness", which centered around a congenial dope dealer, Levine treats the other characters with more respect, and avoids the sentimentality that mars most movies about potentially fatal illnesses--plus, it's a lot funnier. "--Kathleen C. Fennessy"