Impact of Preexisting Mental Illness on All-Cause and Breast Cancer–Specific Mortality in Elderly Patients With Breast Cancer

PurposeLimited data are available on the survival of patients with breast cancer with preexisting mental illness, and elderly women are of special interest because they experience the highest incidence of breast cancer. Therefore, we compared all-cause and breast cancer–specific mortality for elderly patients with breast cancer with and without mental illness.MethodsA retrospective cohort study was conducted by using SEER-Medicare data, including 19,028 women ≥ 68 years of age who were diagnosed with stage I to IIIa breast cancer in the United States from 2005 to 2007. Patients were classified as having severe mental illness if an International Classification of Diseases, Ninth Edition, Clinical Modification code for bipolar disorder, schizophrenia, or other psychotic disorder was recorded on at least one inpatient or two outpatient claims during the 3 years before breast cancer diagnosis. Patients were followed for up to 5 years after breast cancer diagnosis to assess survival outcomes, which were then c...