Then vast majority of experimental treatments are worse than doing nothing. So, it's generally presented as your going to die either way would you like to help find a cure so the situation becomes less hopeless at some point in the future. However, in cases where there is a large demonstrated benifit they often end the contol and give everyone the treatment. Because extending lifespan by 10% is progress but you need a control the demonstrate it's actually better than random chance but a
10+x increase in lifespan needs no control.
PS: Wit is a great movie that deals with terminal illness from the patents perspective. If I recall correctly there is a vary minor subplot around a trial on the proper drug dosage. At no point is the idea that this might be a cure just possibility of slightly extending your lifespan at the cost of a lot of pain. It's basic cost/benifit analysis but taking higher doses is in no way presented as better.
PS: Wit is a great movie that deals with terminal illness from the patents perspective. If I recall correctly there is a vary minor subplot around a trial on the proper drug dosage. At no point is the idea that this might be a cure just possibility of slightly extending your lifespan at the cost of a lot of pain. It's basic cost/benifit analysis but taking higher doses is in no way presented as better.