The Breach Notification Rule is part of the Health Insurance Portability and Accountability Act (HIPAA) that mandates covered entities and their business associates to notify affected individuals, the Secretary of Health and Human Services (HHS), and, in some cases, the media, of a breach of unsecured protected health information (PHI). In the context of cancer care, this rule ensures that sensitive information about cancer patients is adequately protected and that they are informed promptly if their data is compromised.