Sorry you are going through this. I think the best questions are probably the ones you come up with. For me I wanted to know what the treatment was going to achieve and the potential side effects were. I wanted to know what I could do to prepare for treatment and how best to manage myself in the process.
Take someone with you to the appointment as sometimes as they may think of questions to ask as the conversation unfolds.
Also after the appointment you may reflect and then have more questions. So check it's ok to phone back if you think of other questions or if you have a breast care nurse ask them to help with those questions.
Best wishes to you