Schizophrenia and breast cancer incidence. A systematic review of clinical studies

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Schizophrenia Research (Impact Factor: 4.43). 09/2009; 114(1-3):6-16. DOI: 10.1016/j.schres.2009.07.012
Source: PubMed

ABSTRACT Studies examining the incidence of breast cancer in schizophrenia patients report increased, reduced or similar incidence compared to the general population. We undertook a systematic review of published data to investigate possible reasons for the variable findings.
The review was conducted according to the recommendations of the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) group [Stroup, D.F., Berlin, J.A., Morton, S.C., Olkin, I., Williamson, G.D., Rennie, D., Moher, D., Becker, B.J., Sipe, T.A., Thacker, S.B. 2000. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis of Observational Studies in Epidemiology (MOOSE) group. JAMA. 283(15) 2008-2012.]. Methodological issues (Quality Markers) that may explain the variability in the data were identified. Data relating to these issues and the standard incidence rates were extracted. Results were then interpreted in relation to these quality markers.
Data are available from over 6000 female patients with schizophrenia from 13 studies and are reported in comparison to age matched general populations from the relevant country from 1986 to 2008. Although results are widely discrepant ranging from 52% increase in risk to 40% decrease, these data may be understood in terms of cohort age, size and length of follow up as the confounders. Six of 13 studies report an increased or marginally increased incidence of breast cancer. These tend to be studies with more than 100 incident cases of breast cancer, greater than 100,000 person years follow up and older populations.
Breast cancer may be increased in female subjects with schizophrenia. Inconsistencies in study findings may be due to methodological issues such as low statistical power and the age range of cohorts studied. There is no proven risk factor to explain these data; however reduced parity and hyperprolactinaemia may represent putative aetiological factors. Consideration of screening of female patients with schizophrenia for breast cancer is important for clinicians and researchers.

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    • "One of the findings from our previous work in breast cancer is that certain 'quality factors' need to be accounted for when analysing cancer incidence rates, most critically, having a cohort where there is significant follow up after 50 years of age (Bushe et al., 2009). In breast cancer, 80% of incident cases arise in patients over 50 years (Bushe et al., 2009). Even in the Capasso et al. cohort, the median age at study onset was 34 years with a median follow up of 23.5 years, yet the average age of death of patients with cancer was 64 years. "
    Journal of Psychopharmacology 09/2012; 26(9):1285. DOI:10.1177/0269881111430735 · 2.81 Impact Factor
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    • "With respect to specific cancer sites of origin, the results have been inconsistent. For example, some studies have shown an increased risk of breast cancer (Gulbinat et al., 1992; Carlsen et al., 2008; Halbreich et al., 1996; Dalton et al., 2005; Grinshpoon et al., 2005; Hippisley-Cox et al., 2007), while others have shown a decreased (Barak et al., 2005) or insignificant risk of breast cancer (Mortensen, 1994; Lichtermann et al., 2001; Oksbjerg et al., 2003; Goldacre et al., 2005; Bushe et al., 2009). "
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    ABSTRACT: To estimate the incidence and relative risk of developing cancer as well as the mortality rate after cancer diagnosis for patients with schizophrenia compared with the general population. Our population for this study was identified before the end of 1999. The study included 59,257 patients with schizophrenia and 178,156 age- and gender-matched individuals without schizophrenia as controls, who were selected from the 23,981,020 subjects in the National Health Insurance Research Database (NHIRD), which consists of 96% of the entire Taiwanese population. From the 2000 to 2008 NHIRD, we calculated the cancer incidence and survival time after cancer diagnosis in each of the two groups. Based on the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), the cancers were divided into nine groups. During the nine-year follow-up period, 1145 (1.93%) of the patients with schizophrenia and 5294 (2.97%) of the control group developed cancer. The patients with schizophrenia had a significantly lower cancer incidence than those in the control group in both the male (OR=0.50, 95% CI, 0.46-0.55) and female (OR=0.81, 95% CI, 0.74-0.88) populations. Patients with schizophrenia were less likely to develop cancer than individuals in the control group for every cancer type except breast and cervical/uterine cancer. After adjustment using the Cox regression model, patients with schizophrenia had an overall decreased cancer risk (adjusted hazard ratio 0.71, 95% CI, 0.66-0.76) compared to the control population. For all cancer patients, the mortality adjusted hazard ratio for patients with schizophrenia versus the control group was 1.36 (95% CI, 1.24-1.50) after adjusting for other variables. Although the likelihood of developing cancer among patients with schizophrenia (0.64) was less than that of the non-schizophrenia group, the mortality rate among patients with schizophrenia was higher than that of the control group.
    Schizophrenia Research 03/2011; 129(2-3):97-103. DOI:10.1016/j.schres.2011.02.018 · 4.43 Impact Factor
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