One thing that a doctor might agree to do is give your sister a high dose of vitamin C intravenously. It's been known to shock some cancers and give patients time to organize a longer-term treatment plan that doesn't involve the chemo/radiation treadmill.
check out this video
link:
https://www.youtube.com/watch?v=I8I59WJe8c0
There's a lot to read about the high-dose vitamin C treatment by doctors starting with Linus Pauling.
I'm not surprised. I work at a hospital outside the USA, one which has most of the typical departments like cardiology, neurology, oncology, etc. and those depts use the ordinary treatments from Big Pharma and the manufacturers of the radiation therapy crowd. But the hospital also has an Eastern Medicine department that gives more natural treatments (herbal concoctions play a big part but they do other stuff in that dept too, such as pulsed electromagnetic frequency therapy). I have just observed that the cancer patients getting treated in the Eastern Medicine ward tend to live much longer than the ones who go in for chemo/radiation. Also, they save a bunch of money.
Call me cynical, but I have come to think that one of the main purposes of standard cancer therapy is simply to impoverish the patient's family, to make it that much harder for them to do anything to the cabal should they get 'woke'.
Having said that, I think high-dosage vitamin C might not be considered too alternative. IVs of vitamin C are given all the time. It's a question of dosage. I've heard of doctors given 20 to 100 grams intravenously per day (that's grams not milligrams) to cancer patients with good results.