A total of 1,176 cancer patients in Ontario and New Brunswick received chemotherapy cocktails that were watered down, experts say.

Patients in Oshawa, Peterborough, London and Windsor were given cyclophosphamide, used to treat cancers including breast and non-Hodgkin's lymphoma. The premixed bags contained too much saline solution, which diluted the chemotherapy agent, Cancer Care Ontario said Tuesday.

Dr. John Dornan, chief of staff at Horizon Health Network's Saint John zone in New Brunswick, said 186 cancer patients at Saint John Regional Hospital who received watered down chemotherapy since March 2012 are being contacted.

Hospitals received premixed bags of chemotherapy and saline solutions. (Eric Gaillard/Reuters)

The dilution estimates ranged from three to 20 per cent, said Dr. Carol Sawka, vice-president of clinical operations at Cancer Care Ontario.

"It's our understanding right now from what we have heard from the hospitals that they outsourced the actual mixing of two of these chemotherapy drugs to a supplier and the supply that was actually administered to the patient resulted in the patient receiving slightly less than the intended dose of the drugs," Sawka said.

The overall impact on patients is likely low, said Dr. Ken Schneider, chief of oncology at Windsor Regional Hospital.

The Windsor hospital is sending letters to patients today and will followup with phone calls to patients who will be invited to speak to an oncologist about their situation.

No treatment interruptions

"It's really the issue of will that particular drug regimen offer the same degree of benefit to the patients that have received it. In that range of approximately 10 per cent dose reduction of one of a combination of drugs, the likelihood of any serious outcome in terms of relapses of cancer or poorer outcome than unexpected would likely be small," Schneider said in an interview.

Patients received slightly less than the intended dose of chemotherapy, said Dr. Carol Sawka. (CBC)

The premixed bags of a chemotherapy drug and saline solution were prepared by Marchese Health Care in Hamilton, Ont., Cancer Care Ontario said. The supplier produces and labels these medications.

In a statement, the company said it has "built its reputation on meeting the high standards" of the industry.

"We are, of course, deeply concerned whenever any question is raised about the quality of our work. We are collaborating closely with our partners to address the issues which have been raised," it said. "Our preliminary investigation of this issue leads us to be confident that we have met the quality specifications of the contract we are honoured to have been awarded."

Schneider said getting diluted bags of cancer drugs is relatively uncommon. He attributed the error in the cancer cocktail to human error.

The error was identified when a pharmacy technician at one of the Ontario hospitals noticed a discrepancy between what a patient was receiving and what was supplied, Dornan said.

Cancer Care Ontario said some patients who received gemcitabine, were also subjected to a similar dilution problem. Gemcitabine is used to treat lung, pancreatic, ovarian and breast cancer.

Cancer Care Ontario and the affected hospitals are working with the supplier in order to find out the cause of the error.

All four Ontario hospitals immediately removed all cyclophosphamide and gemcitabine received from the manufacturer and secured other supplies, Cancer Care Ontario said. Patients' treatment cycles will not be interrupted during the transition.

Overall, the agency said 990 patients who received chemotherapy treatment with the two drugs since the following dates are affected: