A Mississauga manufacturer of chemotherapy drugs is refuting allegations it mislabelled the medicine it sold to Ontario hospitals.

Marchese Hospital Solutions issued a statement to the media saying the company is confident in the quality of its products.

“We are, of course, deeply concerned whenever any question is raised about the quality of our work," the statement said. "We are collaborating closely with our partners to address the issues which have been raised. 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. Following further inquiries, by our partners and Marchese, we will have more to report in a few days' time.”

Late Tuesday afternoon, Cancer Care Ontario issued a news release saying nearly 1,000 cancer patients in Ontario were not given enough chemotherapy drugs in the last year due to a mislabelling error. About 200 more patients are affected in New Brunswick.

A spokesperson for the provincial agency told CP24.com Tuesday that the drugs were purchased from a single supplier and that the mistake happened at the manufacturing level.

Four hospitals in Ontario gave patients lower than intended doses of chemotherapy between February 2012 and March 2013.

The four hospitals that administered the doses are Peterborough Regional Health Centre, Lakeridge Health, Windsor Regional Hospital and London Health Sciences Centre.

In total 990 patients are affected. A class-action lawsuit was launched Wednesday.

The chemotherapy drugs that were incorrectly administered are cyclophosphamide and gemcitabine, both of which are used to treat a number of cancers, including cancers of the breast and lung. Patients who require treatment for bladder and pancreatic cancer are often treated with gemcitabine. Patients who have been diagnosed with leukemia or lymphoma are typically administered cyclophosphamide.

Impact of watered-down dosage

Health officials say the impact of the watered-down dosage will depend on each individual patient.

“It’s a discussion that must take place between patient and oncologist,” said David Musyj, Windsor Hospital Regional CEO. “There is no specific study that talks about underdosing and if that has a significant negative impact at all, but needless to say, when you are prescribed a significant dose of medication, you want that dose, you don’t want too little or too much.”

Musyj said that all affected hospitals affected are no longer receiving drugs from the manufacturer in question and won’t be until the investigation is complete.

When asked about improving the system’s security process, Musyj said the system won’t work if there’s not a basic level of trust between partners.

“Hospitals don’t prepare drugs on site. There has to be trust in the overall system that the system works,” he said. “This company has been around for quite some time. It’s a reputable company. It’s accredited and it is regulated by Health Canada and it’s inspected on a regular basis.”

Musyj said the investigation will highlight where the problems are in the system and where changes need to be made.

Meanwhile, Health Minister Deb Matthews addressed the issue once again Wednesday afternoon, saying the province is taking action by investigating the matter.

“This is a very serious issue, I can tell you we all take it seriously,” she told reporters at a news conference. “Cancer Care Ontario and the hospitals are investigating, the College of Pharmacists is on site and Health Canada has been notified.

“We expect the highest quality of care and that includes having correct doses of drugs,” she added.

When she was asked who could be held accountable for the error, she said the investigation would have to be completed before that could be determined.

“We must take this very seriously,” she said. “Although oncologists tell me the likelihood of this having a serious impact on patients is slight, it is a very clear indication that we need to be ever vigilant. We’re going to let the investigation unfold. That is the responsible thing to do today."

Matthews pointed to Ontario’s cancer treatment record, saying the province has one of the highest cancer survival rates in the world.

“But we have to ensure we deliver the highest quality of care in order to do that,” she said.

Discovered in March

The problem was discovered in March 2013 by a technician working at the Peterborough hospital.

Tori Gass, public relations for Cancer Care Ontario, couldn't say what led to the technician making the discovery.

Once the hospitals realized the mistake, they immediately took the medication off their shelves and contacted the supplier, the agency said in a news release Tuesday.

The hospitals now have the appropriate dosage in hand to treat patients. Cancer Care Ontario says the patients' treatment cycles will not be interrupted.

Meanwhile, affected patients are being asked to discuss the possible effects of underdosage with their oncologists.

Most of the affected patients -- about 665 people -- were treated in London, Ont. since March 1, 2012. Windsor Regional Hospital underdosed 290 patients since Feb. 24, 2012.

Lakeridge Health undertreated 34 patients since March 12, 2013 and only one patient was affected in Peterborough since March 20, 2013.

@SandieBenitah is on Twitter. For instant breaking news, follow @cp24 on Twitter.