Who'd have thought that the progeny of John Cassavetes - the raging, unruly indie auteur of the 1960s and '70s - would turn out to be such a sap?

Nick Cassavetes had a big hit in 2004 with the mushy, cross-decades love story The Notebook, and now he's piling on the sentiment again, with a lambent adaptation of the Jodi Picoult bestseller My Sister's Keeper.

(OK, to be fair, he did make Alpha Dog in between - a voyeuristic creep-o-rama about teen druggies and botched homicide. But still . . .)

The story of 11-year-old Anna Fitzgerald (Abigail Breslin), and of the whole Fitzgerald family, My Sister's Keeper begins with Anna's voice-over, explaining, "I was engineered with a specific reason . . . to save my sister's life." True enough: Her parents, Sara and Brian (Cameron Diaz and Jason Patric), a lawyer and a fireman, have another daughter, Kate (Sofia Vassilieva), stricken with leukemia.

A compatible donor is needed - for blood infusions, bone marrow, organ transplants - and so, on the advice of their doctor, the couple conceives a child in a Petri dish, using sperm, egg, and the latest in biogenetic technology. From the time she was an infant, Anna has functioned as a spare-parts resource for her sis.

And she's had enough.

That's where My Sister's Keeper starts, with the Little Miss Sunshine tween recruiting a slick lawyer (Alec Baldwin) to petition the court to grant her "medical emancipation" from her parents. Anna wants control of her own body. She doesn't want the giant needles plunged into her hips to suck out the marrow. She doesn't want the horrifying hospital visits. She wants to keep her kidneys for herself.

Selfish? Maybe.

With a screenplay by Cassavetes and his Notebook collaborator Jeremy Leven, My Sister's Keeper is the sort of enterprise that anyone who's had a brush with cancer is going to have a hard time sitting through without reflexively tearing up, and even blubbering.

The scenes of adolescent Kate puking blood, undergoing chemo treatments, experiencing depression, shame, guilt and self-loathing along with the crushing physical hurt - they're tough to behold, even if cinematographer Caleb Deschanel lights and shoots them like he's making a Hallmark movie.

Diaz - as a mom who's forsaken her legal career to take a defiant stand against death, doing everything she can to prolong her daughter's life - is "brave" in that actorly kind of way. There's a scene in which Sara shaves her head, in support of her bald daughter. Diaz didn't actually shave her head, but she does do many of her scenes without makeup.

And Diaz gets her own voice-over monologue, as does Patric - the different points of view functioning like stanza refrains, born in shared familial anguish.

For those who haven't read Picoult's book, My Sister's Keeper offers a couple of twists, one of them crucial and the other cruelly unnecessary and melodramatic. Actually, the crucial twist is steeped in weepy melodrama, too, right down to the bone.EndText