Hocklem , no one knows you as well as you do, and you appear to know yourself really well, based on your post!
As a teacher, you’ll have the summer months to give you time to evaluate all the factors involved in you being and feeling ready to return to work. I’m on-side with Lianne_adminCCS And Brighty : candid discussions with all the “players” - your oncologist, union, administration, and even yourself - are in order. Perhaps something can be worked out with your timetable that you’ll have extra “on call” time that you can lean on if you need it for rest. (It’s been 30 years since I did timetabling at the high school level - I don’t even know if you still have on call time!)
Good luck with your deliberations!