When you’re diagnosed with cancer, you never consider that your shaved head might turn out like Gorbachev’s. Then again, once you hear the word ‘cancer’, everything else has a way of getting tuned out. “It’s a malignant tumour” the doctor might say, to which you’d respond “A tumour?”, like maybe you’d misheard. “Yes” he’d say, a tumour. To this, you’ll turn to look at an otherwise empty consultation room. “Me?” you’ll ask. “Yes” he’ll say, you.

Adam Lerner stares at his oncologist. “That doesn’t make any sense”, and indeed it doesn’t. Cancer rarely does. 50/50 approaches the gloomy spectre with a refreshing flippancy, as if unfazed by the reputation that precedes it. There can’t be much humour in a 27-year-old being handed a coin flip chance at survival, but as a movie about best friends trying to make a go of a bad situation, it’s an appealing rub. Anyway, who wants to spend three maudlin hours exploring what a comedy can do just as well in half the time?

Two buddies and a whole heap of bad luck about sums it up. Adam (Joseph Gordon-Levitt) works for a public radio station with his friend, Kyle (Seth Rogen). A keen runner, a niggling back injury gave Adam little cause to expect anything more than a lecture on proper form. Instead, he was diagnosed with an aggressive form of spinal cancer, to which you might ask: well, is there any other kind? The newly diagnosed all exit into the same state of limbo, in which they are expected to greet a potentially fatal insurgency with patience. While waiting for his treatment to begin, Adam breaks the news to his girlfriend, Rachael, whose expression betrays a young woman not yet ready to care for a sick man. No one signs up for that, least of all a bright, attractive twenty-something. Picture yourself in the same situation, and ask if you could find the strength to pretend otherwise.

As Adam’s mother dutifully fusses and makes plans to move in, Kyle offers something no less profound than more of the same. He gets Adam drunk, high and laid, not because his friend is sick, but because that’s what they’ve always done. It’s rather perceptive of him to recognise that, for all the well-meaning gestures, sometimes all a friend needs to hear is that his shaved head will be a homerun with the ladies. It’s only by consciously ignoring the more accepted modes of sympathy that Seth Rogen is able to surprise us by demonstrating genuine kindness; stoner normalcy in a world falling apart.

Therapist Katherine is new enough to not yet be a doctor, and young enough to miss Adam’s references to Doogie Howser (“Oh, does he work here?”). Nevertheless, their relationship attests to sharp writing that rejects the overwrought emotion of similar scenes in Good Will Hunting. Anna Kendrick follows ‘Up In The Air’ with another attuned performance, whose neuroticism and modesty goes someway to countering the belief that such relationships must always end in romance. The studio pressure to have done so must have been immense, which makes the filmmakers refusal to submit to the wisdom of focus groups an especially laudable one.

50/50 may be slight, but you wouldn’t have it any other way. Despite the subject matter, this is essentially a buddy movie, equal parts endearing, vulgar and insightful; as insightful as you can get about a 27-year-old with cancer, at any rate. Such a thing was never meant for the young, and no film can ever begin to explain cruel, dumb luck. In embracing that, 50/50 is free to explore other, more palatable, possibilities.