Hundreds of cancer patients in at least two provinces may not have received the full doses of their chemotherapy medications and, depending on where they live, may not have been told.

A Manitoba health agency defended the decision not to inform approximately 175 patients who were significantly under-dosed, saying the smaller dose “almost certainly” would not have affected a patient’s outcome and informing them would’ve only caused unnecessary anxiety.

In Ontario, as many as 1,000 patients received less than their prescribed dose over the last decade.

“I think they can be reassured that this is really not a concern. They don’t need to lose sleep over it,” Dr. Piotr Czaykowski, an oncologist and chief medical officer of Cancer Care Manitoba said.

The issue arose after an Ontario health care worker at the Mississauga Hospital alerted authorities to the problem in mid-June, after noticing that medication was being left in the IV tubing of cancer patients receiving chemotherapy infusions.

The hospital employee was concerned because the drugs that were being given to patients were in a highly concentrated form that had been diluted in just a few tablespoons of liquid.

“So the concern was in these patients who got these drugs that are just 50 cc’s, leaving a few cc’s of liquid behind in the tubing meant that they were not getting the full dose,” Robin McLeod, vice-president of clinical programs and quality initiatives at Cancer Care Ontario, told CTV News.

The hospital, part of the Trillium Health Network, asked Cancer Care Ontario to conduct a review and began an internal review of its own.

McLeod says the medications included two immunotherapy drugs used to treat late-stage melanoma, lung cancer, kidney cancer, and head and neck cancer. The third drug was a targeted therapy drug for colon, rectal and other forms of gastrointestinal cancer.

The CCO review found that “more than the expected amounts” of the drugs were being left in the IV tubing of as many as 1,000 patients in 28 different Ontario hospitals.

McLeod says the doctors of those patients were asked to review their patients’ charts. Those physicians decided that fewer than 10 patients needed extra treatment.

She added it’s not known whether any patients experienced negative effects from getting smaller dosages, since determining that answer would be difficult.

CCO found the problem can occur when hospitals use new or different infusion pumps and equipment that might leave drug residues in the tubing. The problem can be remedied if the tubing is “flushed” with saline, but the review found that there is a lack of standardized procedures on flushing.

Flushing is also not always possible when patients have a primary IV line inserted in their chest.

Since similar problems could be occurring at other hospitals, CCO sent a safety bulletin in late June to all 74 hospitals in Ontario that deliver “systemic chemotherapy” to patients.

The bulletin asked the hospitals to review their procedures for ensuring that the intended dosages of “low volume, high concentration” medications reach the patient.

They also alerted other provincial cancer agencies, Health Canada, and ISMP Canada, the Institute for Safe Medication Practices Canada.

Drugs have ‘wide therapeutic window’

About 175 patients in Manitoba were “significantly” under-dosed, which meant more than 10 to 15 per cent of their dosage wasn’t delivered.

But the three drugs all have a “wide therapeutic window,” according to Dr. Czaykowski, which means that an exact dose “almost certainly makes no difference to your outcome.”

“The amount of drug you get, the actual dose you get, if you get a bit more, a bit less, it probably makes very little difference in terms of benefits and very little in terms of side effects,” he said.

Unlike Ontario, Cancer Care Manitoba does not plan to conduct a patient-by-patient review, Dr. Czaykowski said.

He defended the agency’s decision to not inform affected patients, saying it was “far more likely to cause unnecessary anxiety than it was to pose a risk to the patients.”

“And so we took a very deliberate decision and a weighted decision that in this instance, perhaps this was something they didn’t need to know about,” he said.

Even so, Dr. Czaykowski said Cancer Care Manitoba has responded by making appropriate system changes.

“We are making sure that we avoid this in the future,” he said.

Ontario Health Minister Christine Elliott’s press secretary, Hayley Chazan, said her province’s hospitals took necessary steps to correct the issue and informed patients immediately.

“We recognize this can be concerning for patients and their families. Patients who are unsure whether their treatment may have been affected are encouraged to contact their hospital and speak to their physician,” Chazan said in a statement.

Joyce Boa was treated for breast cancer in 2011 at an Ottawa clinic and is now in remission. Earlier this month, she got a phone call. It was the clinic.

“You think everything is over and done with and all of a sudden they are bringing it back up,” she said.

Boa says the clinic informed her that she may not have received her entire dose of chemotherapy due to an issue with the tubing that delivered the drug.

“But they reassured me that everything was good and they usually overfill the bag and not to worry,” she said.

Joyce said she’s already moved on with her life after cancer, and, despite the troublesome phone call, isn’t letting the news get to her.

“I am not going to let it worry me, I am going to put it behind me,” she said.

Finding out that you have cancer is troubling enough, but worrying about improper doses adds a new layer of anxiety, says Jackie Manthorne, a cancer survivor and president of the Canadian Cancer Survivor Network.

Manthorne said it’s critical for all hospitals to inform patients affected by the problem.

“If you are talking about patient-centred care, then patients should know when mistakes like this are made,” she said.

With a report from CTV Medical Correspondent Avis Favaro and senior producer Elizabeth St. Philip