I just checked World First and got a quote for one week including USA/Caribbean. This is the response I got:
The total premium for your policy, including the accepted medical conditions, is: £102.28
We have shown below the status of the declared condition(s) for each traveller and how much extra to cover any accepted condition(s) is included in total premium. You can exclude the declared condition(s) by ticking the box alongside each traveller name and we will recalculate the total premium for your policy, which is shown above.
J. Black (aged 50) screened for:
Condition(s): Multiple myeloma, Anaemia, Impaired kidney function, Chronic renal failure
Status: Accepted
£56.51 to EXCLUDE cover for the declared conditions.
If we have declined to cover your pre-existing medical conditions, or if you choose to exclude them, it will mean any claims arising from the declared conditions(s) will not be covered by your policy.
I also checked for an annual policy for exactly the same conditions, which they declined.
Hope that's helpful for others.