Former U.S. President Joe Biden’s cancer diagnosis reignited questions about whether he deceived the public with his successor Donald Trump during his tenure and added his voice to those who suggested cover-up.

Speaking to reporters at the White House on Monday, Trump expressed doubts about the timing of Biden's advanced cancer diagnosis, due to a scrutiny of physical and mental health during the former president's tenure.

"I'm surprised that the public did not inform the public," Trump told reporters at the White House.

"Why does it take so long? It takes a long time and it takes years to reach this danger," Trump added.

"So, look, it's a very sad situation and I feel very sad about it. I think people should try to figure out what's going on."

Trump also said that doctors who examined Biden during his tenure "didn't tell the truth."

"This is a big problem," he said.

Biden's office said in a statement Sunday that the former president was diagnosed with aggressive prostate cancer and was scattered on the bones.

Biden was diagnosed Friday after experiencing “increased urine symptoms,” and he and his family are reviewing treatment options, the statement said.

The statement said that under the Gleason classification system, doctors classified Biden's cancer into nine points, indicating that it is one of the most aggressive species.

According to Johns Hopkins Medicine, the average five-year survival rate for late-stage prostate cancer is 28%.

Biden thanked the kind-hearted people for their support and encouragement earlier Monday.

“Cancer moves us all,” Biden wrote on social media.

"Like many of you, Jill and I learned that we are the strongest in the broken place. Thank you for promoting us with love and support."

Cancer touches us all. Like many of you, Jill and I learned that we are the strongest in the broken place. Thank you for advancing us through love and support. pic.twitter.com/oss1vgiiwu

— Joe Biden (@joebiden) May 19, 2025

News of Biden's cancer diagnosis is because the former president's health has been under scrutiny before a new book was published, detailing the so-called physical and psychological deterioration that hiding his inner circle.

The original sin, written by CNN host Jake Tapper and Axios journalist Alex Thompson, contains all sorts of nasty claims of Biden’s alleged decline, including the then-President who reportedly failed to know Hollywood actor George Clooney during the 2024 fundraising event.

Trump made a link between the former president's cancer and so-called acumen in his comments on Biden's diagnosis on Monday.

"If you look at it, it's Joe's cognitively good doctor, he's not wrong," Trump said.

He added: "Something that happened is unaware of, and I think someone will have to talk to his doctor."

Some doctors have publicly questioned the description of Biden's cancer diagnosis provided by his office, noting that the advanced cancer must advance within a few years.

Pathologist Steven Quay at X.

"This means that the patient's presence and first being diagnosed with metastatic disease in May 2025 was misconduct. He is likely to have been diagnosed with a prostate cancer diagnosis throughout his White House, and Americans are not getting any information."

Howard P Forman, a professor of radiology at Yale University, said Biden’s cancer was not found to be “unthinkable” before leaving the office because it would be accepted through a blood test called a prostate-specific antigen (PSA) test.

"Before this diagnosis, Gleason level 9 will rise at PSA levels. He has to do PSA tests multiple times. That's weird," Forman said in an article on X.

But while Biden is “very likely” to have years of cancer, he may not have received a PSA test, said Daniel W Lin, a prostate cancer expert at Washington State University.

"There is a screening controversy with PSA, and many medical groups do not recommend PSA testing after the age of 70 or 75, although others recommend recommendations based on life expectancy or health status rather than points of age reduction," Lin told Al Jazeera.

Lin said Biden could also have a rare form of cancer that cannot be detected through tests.

"This is less common, but not uncommon. Also, when this happens, it's more common in advanced cancers, such as the case of former President Biden," he said.

"He won't fall into this category by playing odds, but it will definitely happen."