Increasingly, hospitals are publishing performance results. Look at nhs.uk to see if there is information about the treatment you are considering and which local hospital has the best results.
For a variety of reasons, the information given to patients is sometimes overly optimistic regarding the risks and limitations of treatment. This is changing, but over-optimism is a deep-seated tendency. Perhaps the main obstacle is the use of percentages.
We know that if people are told a treatment will reduce the risk of a disease by 50 per cent, they make different decisions than if they are told the risk will be reduced from one in 2,000 to one in 3,000.
You need absolute numbers, so here are two questions for your doctor:
If 100 people have this test or treatment, how many of them will have a good result?
If 100 people have this test or treatment, how many will suffer some harmful consequence?