Health insurance for family visiting from overseas

I have an aunt and uncle planning on visiting the US from China for a stay of 5 months (on a tourist visa with Chinese passport) and I’m wondering what insurance to get them. They’re about 60 years old and in good health except for one exception — my uncle got liver cancer about 1.5 years ago and had it treated surgically. Apparently they were able to remove all the cancer, and nothing has show up in his few regular checkup CT scans since then. They have health insurance back in China, but no travel insurance as of yet.

First of all, is there any insurance I can buy that would cover potential cancer treatment here if anything returns? (I’m guessing the answer is no)

Second, what sort of insurance should I be looking for (travel, something else?) to cover typical ailments and doctors visits while they’re here?

Thanks!