Between April and June only 70% of patients with an urgent GP referral for suspected cancer started their treatment within 62 days.
The government target is 95%. All health trusts missed the target last quarter.
The figures also show a sharp fall in the number of women first seen within 14 days of an urgent referral for suspected breast cancer.
Only 64%  - 916 of the 1,433 referred patients - were seen within the time limit in June, down from about 80% in June 2015.
Some 9,000 people are diagnosed with cancer in Northern Ireland each year, with incidence rates going up by 11% over the last decade.
Cancer Research UK said the figures showed cancer services are not coping.
"With the number of people being diagnosed with cancer on the increase, the way services are currently organised is not sustainable," said Margaret Carr from the charity.
"This is why a new cancer plan that sets out a long-term vision and identifies priorities and where to target resources, is needed.
"Now is the time to set out new ambitions for cancer in Northern Ireland, along with details of how these goals will be achieved."
Targets for cancer waiting times have again been missed in Northern Ireland.