Jake Thiessen will lead Ontario's independent review of the province's cancer drug supply after more than 1,100 patients in two provinces received watered-down chemotherapy drugs.

The governing Liberals say the review will focus on the drugs that were administered to cancer patients at four Ontario hospitals and one in New Brunswick, some for as long as a year.

They say it will determine how the drugs were watered down and provide recommendations to prevent future incidents.

Thiessen will be assisted by a working group that includes people from the affected hospitals, Cancer Care Ontario, Health Canada, the New Brunswick government and the Ontario College of Pharmacists.

Separate investigations by Health Canada and the Ontario College of Pharmacists are already underway.

Thiessen is the founding director of the University of Waterloo's School of Pharmacy and has previously advised both the Ontario and federal governments.

The discovery of the watered-down drugs in late March prompted Cancer Care Ontario to alert all the affected patients to consult their oncologists as quickly as possible.

There was too much saline added to the bags containing cyclophosphamide and gemcitabine, in effect watering down the prescribed drug concentrations by three per cent to 20 per cent.

The five hospitals all used the same supplier based in Hamilton to prepare the drugs. All have stopped using the drug supply. Saint John Regional Hospital in New Brunswick is now mixing its own.