A powerfully empathetic performance by Joseph Gordon-Levitt saves 50/50 from succumbing to the annoying presence of Seth Rogen and his hophead propagandizing.

Has there ever been as irritating an on screen presence as Seth Rogen? From the movies of Judd Apatow (The 40 Year Old Virgin, Knocked Up) he has become a movie star, yet one that is stuck in a certain mould of which his movies are supposed to conform to, rather than the other way around.

Rogen’s presence in 50/50 as actor and producer is personal. The films is based on the real life experiences of screenwriter Will Reiser, a good friend of Rogen’s who was diagnosed with cancer and survived to tell the tale.

Reiser – for all intents and purposes – is played by Joseph Gordon-Levitt. He stars as Adam, a healthy young man diagnosed with cancer. With an insensitive girlfriend (Bryce Dallas Howard), over bearing mother (Anjelica Huston) and immature best friend (Seth Rogen) not able to provide the support he needs, Adam goes about the gruelling process of cancer treatment on his own.

One of Hollywood’s best young actors, Gordon-Levitt delivers an outstanding turn that is both funny and moving. He sells the fear, the shock, and the exhaustion (mental and physical) of his situation with a heartbreaking clarity that will leave many moved by his plight.

Especially felt is the void of hope which Adam faces. As expected in this Gen Y look at the fleeting line between life and death, the subject of God or religion doesn’t even raise a mention.

Instead solace is found in medical marijuana, here presented as the one and only source of comfort from the hell of cancer. That it’s shown in such a favourable and almost propaganda-like light makes sense when looking at those involved. Director Jonathan Levin’s previous film The Wackness was its own love letter to weed, Rogen always signs its praises high both on and off screen, and on doubt Reiser has his own take on it effects.

Cue a scene where Gordon-Levitt, alongside Philip Baker Hall and Matt Frewer who play fellow cancer patients, seductively smoke a joint with white smoke protruding from their lips like rolling clouds. It’s all skin to a soft porn set scene: all sensual posturing and good lighting, yet so full of BS it’s not worth taking seriously.

It’s many occurrences like that which stops 50/50 from becoming the great movie it should have been. On one hand this is a beautifully portrayed and realised cancer drama. On the other it’s a covert attempt at promoting marijuana, thick with the stench of weed and even more so of Rogen’s stale act.

Reiser’s story and Gordon-Levitt’s performance deserved better.