Impact of preexisting mental illness on all-cause and breast cancer-specific mortality in elderly patients with breast cancer

Purpose: Limited 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. Methods: A 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 compared with those of patients without mental illness. Results: Nearly 3% of patients had preexisting severe mental illness. We observed a two-fold increase in the all-cause mortality hazard between patients with severe mental illness compared with those without mental illness after adjusting for age, income, race, ethnicity, geographic location, and marital status (adjusted hazard ratio, 2.19; 95% CI, 1.84 to 2.60). A 20% increase in breast cancer-specific mortality hazard was observed, but the association was not significant (adjusted hazard ratio, 1.20; 95% CI, 0.82 to 1.74). Patients with severe mental illness were more likely to be diagnosed with advanced breast cancer and aggressive tumor characteristics. They also had increased tobacco use and more comorbidities. Conclusion: Patients with severe mental illness may need assistance with coordinating medical services.