Former President Joe Biden is reducing his public appearances while battling stage 4 prostate cancer, acknowledging that the illness has limited his ability to promote his upcoming memoir, Promise Me, America. The 83-year-old Democrat said Sunday that he would not be able to participate in as many book events and interviews as originally planned.

"Some days are better than others," Biden wrote on social media. "It hasn't stopped me. But sometimes it slows me down." He added that the health challenges would prevent him from having as many conversations about the book as he had hoped.

Biden was diagnosed in May 2025 with aggressive prostate cancer that had spread to his bones. He has since received radiation therapy and hormone treatments, according to The Wall Street Journal. Organizers considered his health when arranging the book tour, although a person familiar with the planning told the newspaper that no events had been canceled because of his condition.

The health developments have renewed scrutiny of Biden's condition, which became a major political issue during his final year in office. He ended his 2024 reelection campaign after a debate performance against then-Republican presidential nominee Donald Trump intensified concerns about his age and ability to serve another term. Vice President Kamala Harris subsequently became the Democratic nominee but lost the election to Trump.

Biden has largely remained out of the public spotlight but has continued communicating with Democratic allies following the November midterm elections. Rep.-elect Dan Koh of Massachusetts told the Journal that Biden left him a congratulatory voicemail after his election victory. Biden also reportedly contacted Pennsylvania Gov. Josh Shapiro and other Democrats who won their races.

The former president is also defending himself against allegations that his cancer diagnosis was concealed while he was in the White House. In his memoir, Biden called the suggestion that he would hide a serious illness "absurd." His diagnosis became public four months after he left office. A spokeswoman cited by the Journal said his last known prostate cancer blood screening occurred in 2014.

In an interview with People published Wednesday, Biden said his cancer had "not metastasized beyond what it already was." He also said he continued to have his mental faculties and felt good, while acknowledging that he was not claiming he would live indefinitely. Biden added that he would not have pursued reelection had he known about the cancer.