The California Office of the Attorney General reported a data breach involving Cancer Treatment Centers of America at Midwestern Regional Medical Center on March 19, 2021. The breach occurred between January 12, 2021, and January 18, 2021, and may have involved the access of personal information including names, medical record numbers, health insurance information, and CTCA account numbers of affected individuals, although financial information and Social Security numbers were not involved.

Cancer Treatment Centers of America sent notification letters to patients whose protected health information was in an employee email account that was compromised by a phishing attack. The attacker was potentially able to access the account for two days, the investigation did not confirm whether any EPHI had actually been accessed, so CTCA is notifying all those potentially affected. CTCA didn't offered those affected by this newest incident any complimentary services because no SSN or financial account information was exposed. It was unclear that how many patients were impacted by the incident.

The California Office of the Attorney General reported a data breach involving Cancer Treatment Centers of America at Western Regional Medical Center on November 27, 2018. The breach occurred on May 2, 2018. The incident involved a data breach that potentially compromised sensitive information, including personal and medical data of patients. This breach could have significant implications for the affected individuals, as it may lead to identity theft, financial fraud, and other forms of misuse of personal information. The breach highlights the vulnerabilities in healthcare data security and the need for robust cybersecurity measures to protect patient information.