Cancer and Mortality in a Psychiatric Population
The incidence rate of cancer in patients with mental illness is similar to that in patients without mental illness; however, overall mortality in cancer patients with mental illness is higher than in the general population. The rate of cancer-related mortality in the population with mental illness is 30% higher than that in the general population. The disparity between incidence and mortality is most marked for prostate and colorectal cancers.
The reasons for the disparity are unclear; if increased cancer-related mortality were due to lifestyle only, the incidence of cancer should be similarly increased. Possible explanations for the disparity may be delayed diagnosis or lack of access to screening, leading to more advanced stage at diagnosis, or reduced access to or use of appropriate treatments following diagnosis.
Researchers recently conducted an analysis to determine why psychiatric patients are no more likely to develop cancer than the general population but are more likely to die from it. They reported results in JAMA Psychiatry [2013;70(2):209-217].
The population-based record-linkage analysis compared psychiatric patients within the Western Australian population. Mental health records in Western Australia were linked with cancer registrations and death records from January 1, 1988, to December 31, 2007. The primary outcome measures of the analysis were metastases, incidence, mortality, and access to cancer interventions.
During the study period there were 135,442 new cases of cancer. Of those, 6586 occurred in people with mental illness. The mean age of psychiatric patients who were diagnosed with cancer was 64.3 years; mean age of patients with no psychiatric history who were diagnosed with cancer was 63.2 years. Among the psychiatric patients, 47.8% (n=3147) were male. Patients with psychiatric history were more likely to live in regional or rural areas and more likely to live in areas in the bottom 20% of socioeconomic status than the patients in the general population who were diagnosed with cancer.
The age-standardized incidence rate for cancer in psychiatric patients was 368 per 100,000 person-years compared with 417 per 100,000 person-years in the general population. This equated to a rate ratio of 0.88 (95% confidence interval [CI], 0.85-0.91). Overall, cancer incidence was lower in the psychiatric population than in the general population for both males and females.
Of the psychiatric patients diagnosed as having cancer, 3056 died during the study period; 51.3% (n=1569) of those who died were male. All-cause mortality and cancer-related mortality were elevated in both males and females in the psychiatric population. The rate ratio for males in the psychiatric population compared with the general population was 1.52 (95% CI, 1.45-1.60); for females, the rate ratio was 1.29 (95% CI, 1.22-1.36).
The proportion of cancer with metastases at presentation was significantly higher in patients in the psychiatric population compared with the general population (7.5% vs 6.5%, respectively). In addition, psychiatric patients had a reduced likelihood of surgery (hazard ratio, 0.81; 95% CI, 0.76-0.86); this likelihood was particularly strong in resection for breast, colorectal, and uterine cancers. Psychiatric patients also had fewer chemotherapy sessions compared with patients in the general population.
