Seth Rogen and Joseph Gordon-Levitt star in '50/50'

NOBODY need tell you that the cancer dramedy "50/50" was written by somebody who's had the disease.

The movie is crammed with been-there details, foremost being a scene in a doctor's office when twenty-something Adam (Joseph Gordon-Levitt) learns, from a robotic physician, that his nagging back pain is caused by a malignant spinal tumor.

Not everybody gets Dr. Kildare.

Some get Dr. Lecter.

There is something despairingly true and funny about the way the stunned, disoriented Adam tries to make sense of the mumbled technical jargon. Gordon-Levitt nails the disorientation, and director Jonathan Levine uses subtle camera moves to chase after the emotionally furtive physician, whose lack of eye contact reveals his clinical detachment.

The scene feels drawn from life, and probably was - Adam is the alter ego of screenwriter Will Reiser, who shaped "50/50" from his own ordeal (and obviously survived to write about it, which seems to change the stated odds a bit).

We don't always get the doctor we want, we don't always have the girlfriend we need. "50/50" also feels true in showing the eroding relationship between Adam and his superficial girlfriend (Bryce Dallas Howard), as emotionally vacant as the doctor and clearly ready to trade a sick boyfriend for a healthy, hipper one.

That's a lot of hard luck for one individual, but "50/50" doesn't make the mistake of turning Adam into a victim/saint. He can be a jerk, particularly in the way he stiff-arms his eager-to-help mother (Anjelica Huston).

Adam is really only comfortable with the practical and emotional support he gets from best friend Kyle (Seth Rogen), whose candor and loyalty make the disease/treatment bearable.

Up to a point. Kyle is reliable, but also exploitive, and actually uses Adam's cancer as a pickup strategy - something that's funny until it's allowed to ferment on screen, and Kyle's behavior (toward Adam, toward women) assumes a darker edge.

It's new territory for Rogen, whose wisecracking and bird-dogging are presented in a different light, making him less funny, more real, and lifting "50/50" out of familiar bromance territory (the movie is more subtle than the trailers indicate).

Also good - Philip Baker Hall and Matt Frewer as chemo buddies who help Adam understand his disease, his situation in life, and his priorities.

These include a potential relationship with his hospital-appointed therapist, the delightful Anna Kendrick, playing another version of the hyperprepared, secretly insecure young woman she gave us in "Up In The Air."