The relief of a successful cancer treatment is all too often marred by a distressing, lingering uncertainty of whether a cancer will return. Cancer cells can tuck away and lie dormant for years before waking up to spread once again. In this episode we speak to Professor Peter Croucher who is tackling some of the toughest problems in cancer research – how can we track cancer cells on their way to becoming dormant, how can we stop them from waking up and how can we eradicate them from our system completely?