On this particular occasion, interviewing Toni Collette and Drew Barrymore is a tearful experience.

Collette starts to cry when talking about how her character in Miss You Already, Milly, a glamorous PR executive, has to face up to the visible toll cancer is having on her in a scene with her best friend, Jess (Barrymore). "The way Drew looked at me in that scene, it was so pure and so loving, and that is actually what the film is about," Collette says, choking on her words.

Barrymore cries while talking about how before she dies, she hopes that her two daughters know how much she loves them. "That's it," she says simply.

I cry when telling them how I valued seeing Milly's chemotherapy sessions in the film. The physical toll aside, it's a rather mundane and repetitive experience shared with a group of sufferers in a bland hospital room. I wasn't with my father for any of his chemotherapy treatments a few years ago before he died, as he lived overseas, but he spoke about it. In this film I got a visual sense of what it would have been like, and I was surprised that it affected me so.

The otherwise good-spirited, charming pair are in Sydney ahead of the film's premiere at the State Theatre on Wednesday night. It's a drama tackling the minefield of negotiating life with cancer, amid the strength of the friendship between the two main characters. The value of Miss You Already is that it doesn't aim to be a chick flick tear-jerker, however.

At its core is the desire to honestly portray cancer as a messy, confusing experience that doesn't come with a handbook. Written by British writer Morwenna Banks, based on her radio play Goodbye, and directed by Catherine Hardwicke who launched the first Twilight film, it's easy to dismiss the film's premise as chick-flick fodder. Where it strikes out is in its humour and realism. Milly can be obnoxious, selfish and makes a lot of mistakes – having cancer doesn't turn her into a saint,

"I didn't want her to suddenly become Saint Teresa," says Collette. "She doesn't make an abrupt turnaround and become somebody else. She takes it on as only she can and makes some really bad decisions and feels justified doing them because she's looking mortality in the eye.

"I didn't want to do a disservice because it's just everywhere, this disease, and it would be wrong and an insult to make it feel saccharine or movie-ish in any way. I just wanted it to be truthful."

Later, Barrymore adds that the strength of the friendship is what characterises the movie. "Goddamn it, maybe this is a f---ing chick flick, and that's OK.

"One minute you're being asked why there aren't enough films for women, and the next minute you're trying to apologise and convince people it's not a chick flick. We've made a film by women for women, about women."

Miss You Already opens on October 8.