I thinks that it depends on the individual...If you really commit to losing the weight you will....I also believe with correct weight workouts you will add muscle tone...The fatigue, I don't know.
I'm in the same situation as you. In my 3rd month of hormone therapy, will start brachytherapy and ERT in early May....Haven't gained weight, but the fatigue factor is awful. Still trying to workout, but difficult....
Good luck to you, and God be with you....