CfDNA in Hereditary And High-risk Malignancies 2

Inclusion Criteria: * Patients with a confirmed diagnosis of hereditary breast and ovarian cancer (HBOC), Lynch Syndrome (LS), Neurofibromatosis type I (NF1), Li-Fraumeni Syndrome (LFS), PALB2, and Hereditary Diffuse Gastric Cancer (HDGC), (i.e., patients with an identified pathogenic variant in the respective cancer predisposition gene, or patients with uninformative genetic testing but with a family history suggestive of the cancer predisposition syndrome). * Patients must be receiving standard-of-care clinical assessment for cancer by a managing physician under a provincial screening program or cancer surveillance protocol. * All patients must have signed and dated an informed consent form for this study. Exclusion Criteria: * Patients must not have a personal history of cancer diagnosed and treated within 3 years prior to the expected first sample collection date for this study. If a patient has a personal history of cancer, treatment must have been completed successfully at least 3 years prior to first study sample collection. * Patients diagnosed more than 3 years prior to the expected first sample collection date, but never been treated for the cancer. * Patients undergoing investigations for a clinical suspicion of cancer. * Patients who are not able to comply with the protocol (i.e., tri-annual blood sample collection if randomized into the experimental cohort).