In 18 months chemo horribly aged and then killed Swayze

And that happened in only about a year and a half.  Swayze ended up dying from his treatment and not his cancer. It was wasting disease that did him in.  Instead of nourishing his body he was advised to starve out his cancer and ended up starving out himself.

  Swayze before chemo          After beginning chemo         Near the end 18 months later

http://www.tbyil.com/Swayze_versus_Survivor.htm