The objective of this protocol is to develop a method to detect early signs of cancer in 'previvors' (people with HCS that do not yet have a cancer diagnosis). This will enable prediction of cancer onset so that patients and their doctors can make decisions to treat or prevent the cancers. HCS patients will be recruited from across Canada to provide blood samples before and after cancer diagnosis. In parallel, there will be development of a circulating tumour DNA (ctDNA) -based test to detect early stage cancer and evaluation on the cost-effectiveness and feasibility of integrating such screening protocols into routine clinical care. In concert, consultation with patients and health care providers will occur to create recommendations for use within clinical care.

