At least when my wife hit that in the Shanghai/Pudong airport (residue from a heart scan, not cancer) they resolved it in a few minutes of talking.
On the other hand, I think Shanghai didn't check well enough--there was one simple test they could have done but didn't: Hand held geiger counter, see what's hot. Body equally hot, baggage not hot, it's medical.
They implemented the system without even thinking of the false positives. Eventually they added that to the procedures, but they harassed quite a few people before that happened. Cancer patients on top of that, many of whom were probably half dead already.
It seems to me that's an awful lot of stupid on their part.
Patient claims medical--call the facility and ask if they should be hot.
However, having read about their stupidity I would be inclined to get a card from the facility even if I didn't expect to be going anywhere with radiation scanners. (My wife had a card--which was sitting at home in the pocket of the jacket she had planned to wear. She changed her mind on flight day and didn't think about the card until she tripped the scanner. Note that she probably had an easier time of it than a typical tourist would have as she speaks Mandarin at native level.)
On the other hand, I think Shanghai didn't check well enough--there was one simple test they could have done but didn't: Hand held geiger counter, see what's hot. Body equally hot, baggage not hot, it's medical.
Why couldn't the US cops do the same thing?