Cancer and travel health insurance: What coverage do you get?

For people who have active and/or advanced cancer, how do you handle health insurance when traveling outside your country with a serious pre-existing condition? Do you just self-insure (roll the dice), or pay extra for special coverage?

I'm interested in hearing from everyone, but especially from Canadians or Europeans traveling to the U.S., because that's where an unexpected hospital visit could really empty your retirement savings fast.