Schizophrenia and Cancer: In 2010 Do We Understand the Connection?

Article excerpt

Objective: In recent years, there has been a plethora of cancer mortality and incidence data reported in schizophrenia. Despite this, there has been little focus on cancer in schizophrenia guidelines. Additionally, there have been suggestions that schizophrenia may provide inherent protection against cancer. The goal of this review is to establish, using recent data, the incidence and mortality rates for cancer in schizophrenia.

Method: We identified systematic reviews and meta-analyses and undertook a search using the Medical Subject Headings' entry terms schizophrenia and neoplasm.

Results: Incidence and mortality rates for cancer in schizophrenia are increased, compared with relevant general populations. Data are not uniformly reported and cohort ages tend to be young for expected cancer incidence. Despite the young cohort ages, the incidence of the major cancers-lung and breast-are substantially increased. Confounders are often not measured in the epidemiologic databases. When lung cancer is adjusted for smoking rates, there appears to be a lower risk of lung cancer than expected providing some basis to support an inherently reduced risk of cancer. There may also be a dissonance between incidence and mortality rates that suggest a prejudice against either diagnosis or treatment of these vulnerable patients.

Conclusion: A single definitive study of schizophrenia and cancer is unfeasible, and future research will lean heavily on systematic review and meta-analysis. Researchers should report cancer data to include age and follow-up data and cohort overlap. Cancer accounts for almost an equivalent mortality as cardiovascular disease.

Can J Psychiatry. 2010;55(12):761-767.

Clinical Implications

* Cancer is more common in schizophrenia, particularly the common cancers of lung and breast.

* Almost as many schizophrenia patients die from cancer as from cardiovascular disease.

* Screening rates are inadequate and many etiological factors are amenable to change or reduction.

* Cancer mortality is significantly greater than in the general population and may be greater than expected from incidence data suggesting suboptimal diagnosis and (or) treatment or increased illness severity.

* Schizophrenia may offer some inherent protection against some cancers, such as lung; however, current data do not allow any definitive conclusions.

Limitations

* No single study can be definitive so conclusions rely heavily on systematic review and meta-analysis.

* The cohort ages in studies are often younger than would be expected to have incident cancer. Few studies include significant cohorts aged 51 years and older for long-term follow-up.

* Reporting of data in many studies is incomplete.

Key Words: schizophrenia, mortality, database, cancer, antipsychotics, breast cancer, lung cancer

Abbreviations used in this article

FEP first-episode psychosis

IRR incidence rate ratio

MRR mortality rate ratio

SES socioeconomic status

SIR standardized incidence ratio

SMR standardized mortality ratio

The physical health of patients with schizophrenia has attracted increasing attention during the last 10 years, with around 60% of the excess mortality related to natural causes and only 40% to suicide and other unnatural causes.1 To date, guidelines from national psychiatric associations, independent bodies, and regulatory agencies have focused on the reduction of selected cardiovascular risk factors. What has been absent is specific attention to cancer.

Mortality rates in schizophrenia remained very high from 1926 to 2000, ranging from an SMR of 1 .5 1 to 3.34.2 The most recent data derive from a 25-year prospective record linkage study3 in the United Kingdom, from 1981 to 2006, which reported an SMR of 2.89. The contribution of cancer to this elevated mortality has been little discussed until recently4'5 despite clear evidence that SMRs for neoplastic diseases are significantly elevated in schizophrenia and there remain 2 further questions. …