Analysis of the incidence and outcomes of breast cancer in women with schizophrenia.

Objective: Breast cancer (BC) is the leading cause of female cancer death in the world and the second leading cause of female cancer death in the U.S, Mortality from breast cancer is even higher in individuals with schizophrenia. The aim of our project was to evaluate the incidence of breast cancer in women with schizophrenia and to compare outcomes between breast cancer patients who were or were not on antipsychotics prior to diagnosis.

Methods: This retrospective study used data from the TriNetX database. Women ≥18 years old diagnosed with schizophrenia were identified. The incidence of primary BC diagnosis between January 2011 and December 2023 was evaluated and stratified by ethnicity. We then conducted a retrospective cohort study to compare outcomes of women ≥18 years who did or did not use antipsychotics one year before BC diagnosis. Patients' propensity score was matched based on age, obesity, tobacco use, socioeconomic status, cancer stage, chemoradiation, axillary lymph node dissection (ALND), sentinel lymph node biopsy (SLNB), and hormone therapy use. Outcomes of interest were 5-year overall survival, recurrence, chemotherapy need, and lymphedema.

Results: 1,398,475 women ≥18 years old with schizophrenia were identified. Breast cancer incidence in these patients was 0.53 ​% in 2011 and 0.53 ​% in 2022, with a peak in 2017 (1.29 ​%). Non-Hispanic patients were diagnosed with BC approximately 1.3 times more than Hispanic patients. The outcomes study included 183,062 matched patients, with 91,531 per cohort. 5-year survival with the Kaplan-Meier analysis was significantly greater in women not on antipsychotics (72 ​%) compared to those on antipsychotics (60 ​%), log-rank test p-value <0.0001. The risk of local recurrence (13.4 ​% versus 22.6 ​%, p-value <0.0001), chemotherapy need (41.2 ​% versus 48.4 ​%, p-value <0.0001), and lymphedema (7.7 ​% versus 11.5 ​%, p-value <0.0001) were also significantly lower in women who did not take antipsychotics.

Conclusion: Breast cancer incidence in patients with schizophrenia identified through TriNetX has not experienced a significant uptrend or downtrend over the past decade. Non-Hispanic patients with schizophrenia have a higher incidence of BC than Hispanic patients. Matched breast cancer patients on antipsychotics at least one year prior to diagnosis had higher mortality, recurrence, chemotherapy need, and risk of lymphedema.