How does your aunt feel about all this? Although she's 82, she personally may not feel she's "too old" te get treated. My Dad became critically ill at the age of 81 (not cancer), and he fought like hell for 5 months to survive...he wanted to live. None of the doctors and nurses acted as if we should write him off just because of his age.
Having said that, of course there are different concerns with cancer because the treatments can be harsh, although not always. First of all, radiation can have side effects, but most people go through it without much trouble at all. You might get a little bit tired, but then again, you might not. My mother had 3 separate courses of radiation treatment and never missed a day's work, and she was in her 60's and early 70's when she was treated. Last fall I went through radiation treatment and had no side effects whatsoever (except for minor skin burning, which didn't occur until near the end of treatment and healed within a couple of weeks after treatment),
Chemotherapy...well, it depends on what kind. Some kinds are easier to take than others. Also, there are many wonderful anti-nausea medications on the market that completely control the nausea. I actually gained weight during chemotherapy.
Probably the best thing to do is to sit down with the doctors and your aunt and ask the questions: A) what kind of chemo, what are the anticipated side effects? B) how much radiation, how big an area, what are the anticipated side effects? C) If your aunt goes through all this, what is the projected outcome? How much longer do they anticipate extending her life; how will the quality of her life be affected? Also, if she DOESN'T go through any treatment at all, what will her quality of life be like between now and the time she finally succumbs to the cancer. Sometimes chemotherapy can be "palliative", meaning it's not expected to cure the cancer, but can actually make the patient more comfortable, especially if it's a type of cancer that typically spreads all over the body but takes a long time to actually cause death. Certainly you don't want her to end up suffering for months and months.
These are all very hard questions, both to ask, and to hear answered. Don't forget, too, that she can always start treatment and then decide to stop it at a later date if she isn't getting better and feels she'd rather let go than tolerate the side effects of treatment.
Please make sure your that your aunt is not only fully informed, but that her wishes are respected...those are the two kindest things you can do for her. And I wish you all the strength in the world to help you and your family through this difficult time.