Joe Biden is having radiation therapy to treat an aggressive form of cancer diagnosed earlier this year.

“As part of a treatment plan for prostate cancer, president Biden is currently undergoing radiation therapy and hormone treatment,” according to the spokesman for the former president.

The former US president, 82, had already been taking hormone therapy in pill form.

In May, he was diagnosed with an aggressive form of prostate cancer that has spread to his bones.

The new treatment marks a new phase in his therapy and is expected to last five weeks, the spokesperson told NBC News.

Mr Biden, the oldest president in history, has kept a low profile since leaving office.

He is working on a memoir and has occasionally been seen on the Amtrak train between his Delaware home and Washington, DC.

Last month, he also had treatment for skin cancer. He underwent Mohs surgery to remove a cancerous growth and was spotted with a bandage on his forehead at that time.

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