Officials were moving to contact seven other patients who had suffered clinical setbacks. They have brain, neck and prostate cancer.
Hundreds of others treated on a faulty linear accelerator at Royal Adelaide Hospital between 2004 and 2006 would be unaffected, a review has concluded.
The South Australian Health Department chief executive Tony Sherbon said the lower than prescribed doses of radiation they received may have affected their ability to control their disease, but they would not require more treatment and would now be closely monitored. The state Health Minister John Hill said the impact would have been "small, but real."
In all, 869 cancer sufferers were given a 5 per cent lower than prescribed dose of radiation during treatments over the two-year period from a machine that was incorrectly calibrated.
At the time, doctors and management at Royal Adelaide Hospital determined that the underdosing was not significant and did not inform the Health Department or ministry.
Dr Sherbon ordered an independent review, led by radiation oncologist Geoff Delaney, when told of the problem in July.
Professor Delaney reported: "In terms of clinical significance, it is likely that almost all patients will have not suffered as a result of the radiotherapy underdose because the underdose was relatively small."
A separate independent review will now examine why the matter was kept secret.
Professor Delaney made 14 recommendations to ensure the mistake would not be repeated. The South Australian Government has accepted all of them.