Alzheimer's is 100000x worse than cancer. I'll make that argument any day. My Grandmother was the youngest of 12, 8 girls, 4 boys. Three of the boys died in WW2, four of the girls dies of things like polio, measles etc. The remaining women, with the exception of my grandmother, all slowly slipped away as their bodies kept chugging along. One of my aunts was arguably one of the wittiest, funniest, sharpest people in my life. Watching that light go out over a decade was worse than watching a family friend's body get eaten by cancer. At least with cancer you get to remain 'you' for lack of a better way.
Taking care of a parent is rough, and hope that you get to have some down time. Doing the right thing by those we love and care for sucks, don't it.