My husband has battled aggressive bladder cancer for 5 years now. I recommend doing some reading on Mayo Clinic and other large cancer centers to familiarize yourself with bladder cancer. It will help when talking to his doctors and gives you some questions to ask.
There is a book that I loved for the information I gained from it when I was diagnosed with cancer 12 years ago. It includes information on nutrition. I bought copies for my family members on Amazon. “How Not to be My Patient” by Edward Creagan MD. He is a palliative care physician at Mayo and his writing is so helpful.
Do you have a treatment plan set up yet with your urologist?