The London Health Sciences Centre is one of four Ontario hospitals where cancer patients were given lower than intended chemotherapy doses.

About 990 patients in the province are believed to have affected, including 665 at LHSC. Patients at hospitals in Windsor, Oshawa and Peterborough are also involved.

Cancer Care Ontario said in a statement released Tuesday that “affected patients are being encouraged to discuss the possible effects of the under-dosing with their oncologists.”

The medications, cyclophosphamide and gemcitabine, were purchased from a drug manufacturer.

The problem was discovered in late March, and relate to chemotherapy treatments administered at LHSC starting on March 1, 2012.

All hospitals have since stopped using the incorrectly dosed medications.

Cancer Care Ontario said the organization and local hospitals are working with the supplier to determine the cause of the error.

London-area patients with concerns can contact LHSC at 519-685-8805 or 1-855-464-3262 or visit: