Your questions are the right start. From my mother's cancer, I've learned that you shouldn't trust the medical professionals to have your best interest at heart. I'd ask:
1. Actual cancer diagnosis. What is the name for this specific kind? How does this cancer behave?
3. Preferred Treatment options.
4. List of risks associated with this treatment, and the odds of those risks.
5. Copy of study on said treatment for your review, so you can check their math.
6. List of other treatment options, their success rates and associated risks.
7. Plan in case of failure of first treatment.
8. Effects of not treating this cancer at this time.
Always check the information they provide. My mother was recommended an allotransplant (bone marrow from yourself). The doctors assured her that the odds of curing (not remission mind you) her cancer were 90%, with a 10% mortality. That is flat out untrue, and no one checked the math. We're lucky she lived. The treatment has over 50% mortality in the first year.
If chemo or any form of drug / intravenous treatment is issued, I would recommend that your sister have a family member present at each treatment to personally check the drug and dosage. My mother's second treatment was never administered in the proper dosage. (but I was already on to them from the previous deception. I was present for every treatment, and corrected it every time.)
Whoever is present for this needs to be strong willed and the kind of person who won't take crap from anyone. Standing up to the nurses can get the police called, so be ready for that. They don't take well to having their authority or expertise questioned. A PoA (flat out, not "Durable") cured this problem in my jurisdiction.
Point of reference any doctor that claims a cure for cancer is a quack. The language is "treatment". There is no cure for cancer, we can screen for it (early hopefully) and then treat it for the best outcome possible.
I'm sorry to hear your mother had to endure this poor treatment. Most oncology teams in my experience are very good at what they do.
Most teams of medical professionals are great at what they do.
I'm all too familiar:
1998 my wife and I moved in with in-laws to take care of my FIL who was in stage four of stomach cancer that had already spread to his liver. We cared for his pain management for seven months so he could die at home surrounded by family.
2005, my sister spent seven weeks in intensive care before we had to make the decision to remove her from life support. The autopsy revealed an aggressive astrocytoma (most common form of brain tumor) in her brain stem. This is an untreatable form of cancer.
Sending you and Pluto aloha.
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