Sounds to me like you need to take some more time to recover first.
You articulated so well why breast cancer is such an awful disease. It isn't a simple situation. It really does your head in.
For now though I hope you can congratulate yourself, at least a little bit, on getting through round 1. You got rid of the local cancer and you survived chemo and radiation. That takes time to get over.
Can you get your team to buy you some space in which to get strong again before starting round 2? Get their reassurance that a month here or there won't matter.
These are big decisions to make.