Well, I'm not in a position to talk Paget's or breast cancer, but I do have an octogenarian Mom (88) who was diagnosed with pancreatic cancer last winter. They did a pretty radical surgery on her (modified Whipple surgery) in April. She's doing well now but has lost some of her stamina. Her attitude has been that she is ready to go and doesn't really want to live forever. She's not actively seeking death or anything, but she didn't want chemo because she didn't want to be sick for her final years. She's traveling again (down the Danube with a marathon flight home from Istanbul) and is generally OK.
If you haven't, I suggest talking to your Mom about her expectations. Death may not be unwelcome.