In the US - and from my own personal experience - people tend to 'wait and see' before they go to the doctor.
the thinking behind this is simple
'this may just be a change in my normal cycle, that pain might be nothing...... so, do I pay for a doctor or wait until i get so bad, i have to take time of work'
in a country with socialized healthcare, like the UK, the person will probably go to the doctor a lot sooner than in the USA
so, the (arguably) better medical care in the USA will be cancelled out by the fact that the UK patient will be treated sooner, before things get out of control.
and yes, I have seen this scenario played out directly with people who have had cancer treatment in Utah and London