Former President Joseph R. Biden Jr.’s prostate cancer has spread to other parts of his body, leaving him in pain, his son Hunter Biden said in an interview broadcast on Friday.

“It’s metastasized into his bones and further,” Hunter Biden told a BBC journalist. “It’s very painful and it’s very debilitating, in many respects.”

The former president, 83, was diagnosed in May 2025 with an aggressive form of prostate cancer, his office revealed at the time. Last year, he had surgery to remove skin cancer lesions and completed a round of radiation therapy. His daughter, Ashley Biden, posted a video of Mr. Biden ringing a bell, a tradition that patients perform to mark a major treatment milestone.

The diagnosis did not prevent Mr. Biden from making some public appearances. He recently delivered the keynote address at a fund-raising event for the Maryland Democratic Party, on what happened to be the two-year anniversary of a disastrous presidential debate performance that effectively ended his re-election campaign.

“He’s still out there,” Hunter Biden said in the interview broadcast on Friday. “As long as he’s alive, I promise you, he is going to continue to fight.”

Prostate cancer is typically a slow-growing disease that affects older men, and can be present for years without symptoms or a diagnosis. Advanced cases often spread to the bones, like the former president’s has, Jill Biden, his wife and the former first lady, said in a podcast interview this week with Kelly Ripa, the talk-show host. Once the cancer gets in the bones, medical experts say, it cannot be cured.

Dr. Biden said that her husband’s treatment was continuing.

“He will forever live with cancer,” Dr. Biden said. “It’s constant. It’s daily. And I think it’s challenging.”

Mr. Biden, who has long supported cancer research, has already dealt with family tragedy related to the disease. His son Beau died in 2015 of glioblastoma, an aggressive form of brain cancer.

Mr. Biden has had many health problems, including a brain aneurysm in 1988 that threatened to end his political career.

The former president plans to release a memoir titled “Promise Me, America” shortly after the November midterm elections.