I normally prune ours back in the autumn once all the fruit has been picked but you can prune it now before it breaks out into new growth. New shoots tend to grow quite vigorously, so it depends much much you want to trim off. The dead canes will probably have gone all brown by now so they can be removed. The green canes are the ones which will shoot soon and bear the flowers. You can safely cut the bush back at least half and it will soon regrow.