The figures come from the World Trade Centre Health Programme, a US government scheme which helps victims of 9/11 with medical care.
In total 9,795 people, including many heroic first respondents, have cancer which is deemed to be 9/11 related.
Of these 420 have died.
John Feal, from the Feal Good Foundation which campaigns for those affected who survived the attacks, told the New York Times: “9/11 is still killing.
“Sadly, this fragile community of heroes and survivors is shrinking by the day.”
The number of 9/11 related cancers has increased dramatically since the government programme began tracking cases in 2013.
Cancers often appear many years after exposure to harmful substances.
Dr Michael Crane, the medical director of the WTC Health Programme at Mount Sinai Hospital in New York, said: “We get these referrals 15 to 20 times a week.”
The link between exposure to the 9/11 attacks in New York and serious health problems has been acknowledged for years.
A study published one year after the attacks noted that many victims were suffering from what it described as the “World Trade Centre cough”, and noted that many first respondents were suffering from respiratory problems.
It’s been found that 9/11 rescue workers have significantly higher rates of skin, thyroid and bladder cancer than the general public.
Victims also have notably higher rates of breast cancer and non-Hodgkin’s lymphoma.
The 9/11 attacks on the World Trade Centre in New York and the Pentagon in Virginia, killed 2,996 people directly.
Another 6,000 were left injured.
The attacks were carried out by 19 members of the al-Qaeda terror group, who hijacked four commercial airliners and flew them into their targets.
One airliner crashed in Shanksville, Pennsylvania, after passengers attempted to storm the cockpit before it reached its target.