Former U.S. President Joe Biden, 83, has prostate cancer that has metastasized to his bones and causes him pain, his son Hunter Biden said in a BBC interview broadcast Friday. Biden was the oldest man to serve as president and his health has drawn attention since he left office. He disclosed the diagnosis in May of the previous year, less than four months after leaving the White House. Hunter Biden said the condition has been difficult for the family and noted that his father continues to speak publicly about issues he cares about. He added that Biden remains active and plans to publish a memoir titled "Promise Me, America" after the mid-term elections. The impact of the disease on his public role has not been specified.