Hi, I had a friend that had a brain tumor, required surgery and Immunotherapy.
18 months on, he is doing well, started back his cycling small stuff to begin with and built up to cycling 60-70mile rides and some big hills. He has to be careful with COVID 19 around due to his immune system being compromised with the continued treatment. His main feedback was take it in small steps and listen to what your body tells you.
Found this link also.
Take care of yourself!!
