326 cancer patients got wrong radiation dose due to math error
http://www.cbc.ca/health/story/2008/...ke-080421.html
ast Updated: Monday, April 21, 2008 | 6:06 PM ET
Excerpts

Hundreds of skin cancer patients received the wrong dose of radiation over
a three-year period due to a calculation error programmed into one of the
radiation units at the Ottawa Hospital Cancer Centre.

The 326 patients received a dose of as much as 17 per cent less than the
prescribed dose while being treated between November 2004 and November
2007 for basal and squamous cell carcinomas, the Ottawa Hospital said in a
news release Monday.

Those types of skin cancers typically don't spread and tumours usually can
be successfully removed or treated with radiation. Patients with more
aggressive melanoma skin cancer were not affected.

The calculation error was programmed into a radiation unit in November
2004, when it was moved from the general campus to the civic campus of the
Ottawa hospital, being assembled and disassembled in the process.

The mistake arose because the radiation is measured for a particular size
of radiation beam, and calculated for the other beam sizes using a formula
that contained an incorrect number.

The error was discovered in November 2007 by measuring the radiation at
other beam sizes using a dosimeter, Carruthers said.

It was immediately corrected, the hospital said. Other radiation units
were also checked.

Despite the error, 294 people got the right radiation dose because they
were treated with the beam size used to calibrate the machine.

Patients who:

* Received radiation treatment for basal cell or squamous cell
carcinomas.
* Were treated from November 2004 to November 2007.
* Were treated at the civic campus of the Ottawa hospital.

Concerned patients can reach a special information line by calling [see
webpage]