Female schizophrenia patients and risk of breast cancer: A population-based cohort study.

OBJECTIVE: Breast cancer is the most common type of cancer in women. This population-based cohort study aimed to examine the association between breast cancer in female schizophrenia patients and its association with the use of antipsychotics drugs.

METHODS: All study subjects were selected from the Taiwan Insurance Claims Data (1998-2008). We compared the risk for breast cancer between female schizophrenia patients receiving antipsychotics (n=29,641) with female patients without any serious mental illnesses nor receiving antipsychotic drugs (n=59,282). We also compared between patients on 1) first-generation antipsychotics (FGAs) alone; 2) combination of first and second generation antipsychotics (SGAs); and 3) SGAs alone. We then stratified those on SGAs into two subgroups according to their prolactin-elevating properties: risperidone (RIS), paliperidone (PAL) or amisulpride (AMI) and all other SGAs.

RESULTS: After adjusting for confounding factors, the risk of breast cancer in female schizophrenia patients was 1.94 higher than the non-schizophrenia cohort (aHR: 1.94, 95% CI: 1.43-2.63). Schizophrenia patients receiving a combination of FGAs and SGAs had a slightly higher risk of breast cancer than non-schizophrenic patients (aHR: 2.17, 95% CI: 1.56-3.01). Patients on RIS, PAL, and AMI had a 1.96-fold risk of breast cancer compared to the non-schizophrenic cohort (95% CI: 1.36-2.82).

CONCLUSIONS: This study raises awareness among both clinicians and patients about the importance of breast cancer screening and the promotion of healthy lifestyle choices. Due to the nature of our database, confounding factors - such as parity, obesity, hormone therapy, and smoking - could not be controlled for.