"I saw a medical oncologist who reccod active surveillance as did the chairman of the urology deparment at Univ of Miami"
Therein is your answer.
" My niece who is brilliant and in med school feels strongly that the only answer is surgery (by the way she is not going to become a surgeon)."
She could well be brilliant. (by the way, she is not a medical oncologist or chairman of the urology department at Univ of Miami either)
Your wife might not tend to minimize illness as you suggest: maybe she thinks that the medical oncologist and chirman of urology deparment know what they are talking about