Former President Joe Biden has been diagnosed with an aggressive form of prostate cancer that has metastasized to the bone, his office announced this week. The cancer diagnosis also comes amid renewed questions about his mental and physical fitness before leaving office due to a slate of new books from reporters claiming Biden was dealing with cognitive decline at the end of his presidency,

"[Biden] did not develop it in the last 100, 200 days. He had it while he was president," oncologist Ezekiel Emanuel said Monday on "Morning Joe."