The Ottawa Hospital Cancer Centre says 326 cancer patients received a lower dose of radiation treatment than prescribed to them over a three year period due to a calculation error.

The cancer centre says the mix-up was a result of human error and happened when a radiation unit used to treat two common skin cancers was moved from the General Campus of the Ottawa Hospital to the Civic Campus in November 2004.

"When the unit was reconstructed in its new location and recalibration took place, there was an error in treatment dose calculation," read a press release issued to the media on Monday.

The cancer centre says patients who received radiation treatment between November 2004 and November 2007 got a dose of radiation up to 17 per cent less than the dose prescribed to them.

The head of the Ottawa Hospital says a staff shortage was likely one of the factors that led to the mistake.

"A factor at that time was probably that we were short of staff of physicists, but health care overall is under a significant challenge be it physicists, be it MRI technicians, be it nurses - our times are short-staffed," said Dr. Chris Carruthers, Chief of Staff of the Ottawa Hospital.

Patients affected by the mistake include those who:

  • Received radiation treatment for a Basal Cell and Squamous Cell carcinomas
  • Were treated between November 2004 and November 2007
  • Were treated at the Civic Campus of the Ottawa Hospital

Medical officials are advising the public that patients who received treatment for any other type of cancer have not been affected by the mix-up.

The centre says the error was discovered in November 2007 and the dose rate was immediately corrected to the appropriate level. Officials say no further treatments have been affected since the mistake was discovered.

The Ottawa Hospital is now in the process of contacting each patient who received incorrect treatment over the three-year period.

Oncologists are also reviewing the medical charts of all 326 patients affected by the error. The process is expected to be complete by Tuesday.

The hospital says it is currently changing the way radiation machines are tested to help prevent this kind of mistake from happening again in the future.

The cancer centre says it immediately undertook an internal review of the issue and later contacted an expert medical reviewer based in Toronto to determine the clinical impact of the mistake.

Concerned patients can call an information line at 613-739-6800 or toll free at 1-866-253-2603.