Of the nine patients affected, eight have since died.
In one tragic case, a significant chance of a cure through surgery was missed due to the mistake.
Problems were first notified to the local HSE in September last year.
Eight months later, the executive announced a full look back and notified the families concerned.
That review involved thousands of x-rays and other scans taken at Our Lady of Lourdes Hospital, Drogheda, and Our Lady's Hospital in Navan between August 2006 and August 2008.
The review says that the delays had 'varying impacts on these patient's care and treatment options'.
This includes lost opportunities to provide cures, additional life span and earlier palliative care.
The delays also led to worry, uncertainty and distress for the families and reduced time for them to come to terms with the impending death of their loved ones.
Consultant 'devastated'
In today's 60-page report, released by the HSE on its website, the temporary consultant radiologist concerned said he was devastated by the findings and wished to apologise to the families for the anguish and sorrow caused.
Following the publication of the report today, the HSE said they were going to enhance clinical governance in the radiology in the five hospitals in the northeast.
The review of 5,835 x-rays and 67 CT scans found that the majority of patients did not require further treatment.
A total of 4,628 patients need no action while 270 had a problem that should have been reported but the fact that it was not does not have any clinical significance.
A total of 29 patients could not be retrieved and were the subject of a separate follow up.
Today's report of the review also reveals that 179 letters were sent to patients who had died, causing distress to their families and relatives.
The HSE had engaged a mailing company to undertake the postal communications given the logistical challenge.
Read the full HSE review here
