Australia's most infamous serial killer Ivan Millat has been diagnosed with terminal cancer and is unlikely to return to solitary confinement at Goulburn Supermax Jail.

Key points: The 74-year-old underwent a series of tests on lumps found in his throat and stomach

The 74-year-old underwent a series of tests on lumps found in his throat and stomach Milat has never shown remorse for the brutal murders of seven backpackers in the 1980s and 1990s

Milat has never shown remorse for the brutal murders of seven backpackers in the 1980s and 1990s He is chained to his hospital bed with two prison guards on 24-hour surveillance

The 74-year-old was driven to the Prince of Wales Hospital in Sydney's east on Monday, where he underwent a series of tests on lumps found in his throat and stomach.

The ABC understands Milat has oesophageal cancer which has spread to his stomach, but it is unclear how long he has to live.

Known as the Backpacker Killer, Milat has never shown remorse for murdering seven travellers — some of whom were stabbed, shot and beheaded.

Their bodies were found in unmarked graves in the Belanglo State Forest between 1989 and 1993.

The former road worker was handed seven life sentences in 1996.

He has lost 20 kilograms over the past few months, with a source close to his family saying he was suffering from geriatric anorexia and was "dangerously thin".

But prison sources told the ABC he would constantly refuse food or swallow sharp objects like paperclips and razor blades if guards did not meet his demands.

Milat will likely be transferred to Long Bay Prison hospital.

Milat, who constantly complains about prison food, recently once threatened self-harm when his toasted sandwich maker was confiscated because of "bad behaviour".

When he was admitted to the hospital ward for inmates at Randwick, the "high risk" prisoner was tested for possible organ failure linked to rapid weight loss.

But instead, Milat was told he was in the "advanced stages" of cancer, and that he would most likely be transferred to Long Bay Prison Hospital in Sydney's south.

The ABC understands his nephew Alistair Shipsey phoned the Prince of Wales Hospital but was prevented from contacting his uncle, who is also showing signs of dementia.

Milat remains chained to his hospital bed, with at least two prison officers guarding his room and providing 24-hour surveillance.

Arrangements are being made to move him to another correctional facility, but that may take some time, given his recent diagnosis.