Researchers at Toronto's Princess Margaret Cancer Centre have launched a major study to see if a simple blood test can detect microscopic traces of cancer left behind after treatment. If successful, it could allow doctors to identify a cancer recurrence long before it appears on a scan. To talk about this potential breakthrough, Tamara is joined by Dr. Lillian Siu, medical oncologist at Princess Margaret Cancer Centre, Professor of Medicine at the University of Toronto, and Scientific Lead of the Peter Gilgan Centre for Early Cancer Detection Research.