Impact of a pre-existing diagnosis of mental illness on stage of breast cancer diagnosis among older women

Purpose Having a mental illness increases risk of mortality for women with breast cancer, partly due to barriers to accessing recommended care (e.g., cancer screening). Early detection is one important factor in breast cancer survival. To further understand this disparity in survival, we examined whether older women with mental illness are more likely to be diagnosed with later-staged breast cancers compared to women without mental illnesses. Methods We used 2005-2015 SEER-Medicare data to identify AJCC stage I-IV breast cancer patients with and without a history of mental illness prior to cancer diagnosis. We used generalized ordinal regression to examine associations between mental illness diagnoses and stage at diagnosis, controlling for age, race/ethnicity, income, comorbidities, primary care use, rurality, and marital status. Results Among 96,034 women with breast cancer, 1.7% have a serious mental illness (SMI), 19.9% depression or anxiety, and 7.0% other mental illness. Those with SMI have 40% higher odds of being diagnosed with AJCC Stages II, III than Stage I; women with depression/anxiety have 25% lower odds of being diagnosed with Stage IV cancer than Stage I; and women with other mental illnesses have similar odds of being diagnosed in later stages. Conclusion Women with SMI have higher odds of being diagnosed at later stages, which likely contributes to higher mortality after breast cancer. Surprisingly, women with depression and anxiety have a lower risk of being diagnosed with Stage IV cancer. Earlier breast cancer diagnosis in women with SMI is an important goal for reducing disparities breast cancer survival.