The disease has already metastasised, though a statement said there were options for "management".
US President Donald Trump has sent his "warmest wishes" toward his old rival, former President Joe Biden, after the latter's office revealed he was diagnosed with an "aggressive form" of prostate cancer.
"Last week, President Joe Biden was seen for a new finding of a prostate nodule after experiencing increasing urinary symptoms," the statement from Biden's personal office said.
"On Friday, he was diagnosed with prostate cancer, characterised by a Gleason score of 9 (Grade Group 5) with metastasis to the bone."
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It continued, "While this represents a more aggressive form of the disease, the cancer appears to be hormone-sensitive which allows for effective management."
Biden and his family "are reviewing treatment options with his physicians," the statement said.
Trump, who Biden defeated in the 2020, put politics aside in a message posted on his Truth Social profile.
"Melania and I are saddened to hear about Joe Biden's recent medical diagnosis," Trump said.
"We extend our warmest and best wishes to Jill and the family, and we wish Joe a fast and successful recovery."
Biden's vice president, Kamala Harris, said on social media that she was keeping him in her family's "hearts and prayers during this time."
"Joe is a fighter — and I know he will face this challenge with the same strength, resilience, and optimism that have always defined his life and leadership," Harris wrote.
Former President Barack Obama said his thoughts and prayers were with Biden, his former vice president, lauding his toughness.
"Nobody has done more to find breakthrough treatments for cancer in all its forms than Joe, and I am certain he will fight this challenge with his trademark resolve and grace," Obama wrote on social media.
The health of Biden was a dominant concern among voters during his time as president. After a calamitous debate performance in June while seeking reelection, Biden abandoned his bid for a second term. Harris became the nominee and lost to Trump, a Republican who returned to the White House after a four-year hiatus.
But in recent days, Biden rejected concerns about his age despite reporting in the new book "Original Sin" by Jake Tapper and Alex Thompson that aides had shielded the public from the extent of his decline while serving as president.
In February 2023, Biden had a skin lesion removed from his chest that was a basal cell carcinoma, a common form of skin cancer. And in November 2021, he had a polyp removed from his colon that was a benign, but potentially pre-cancerous lesion.
In 2022, Biden made a "cancer moonshot" one of his administration's priorities with the goal of halving the cancer death rate over the next 25 years. The initiative was a continuation of his work as vice president to address a disease that had killed his older son, Beau, who died from brain cancer in 2015.
His father, when announcing the goal to halve the cancer death rate, said this could be an "American moment to prove to ourselves and, quite frankly, the world that we can do really big things."
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