The incidence of cancer is lower in psychiatric patients than the general population, but associated mortality rates are higher, researchers report.
Stephen Kisely (University of Queensland, Herston, Australia) and colleagues also found that psychiatric patients with cancer were more likely to present with metastases and less likely to receive radiotherapy and chemotherapy than cancer patients in the general population.
"In terms of clinical practice, this study suggests that psychiatric patients experience similar difficulties with access to cancer care as for cardiovascular care. This may contribute to higher case fatality rates in illnesses for which the incidence is no higher than that of the general population," say the researchers.
Using mental health, cancer registration, and death records, the researchers compared cancer incidence and mortality rates between psychiatric patients and the general population of Western Australia for the period 1988-2007.
In total, 135,442 individuals developed cancer during the study period, of whom 6586 had been diagnosed with a psychiatric illness.
The researchers found that the age-standardized incidence rate for cancer was lower in psychiatric patients compared with the general population, at 368 versus 417 per 100,000 person-years, equating to a rate ratio (RR) of 0.88 among psychiatric patients. Among psychiatric patients, men had a lower incidence of cancer than women, at an RR of 0.86 versus 0.92, compared with the general population.
However, cancer-related mortality was higher in psychiatric patients than the general population, at RRs of 1.26 in men and 1.15 in women, with the highest RRs among patients with schizophrenia and other psychoses.
Furthermore, psychiatric patients with cancer were significantly more likely to have metastases at presentation than other cancer patients, at 7.1% versus 6.1%.
Psychiatric patients with cancer were also less likely to receive surgery, particularly for colorectal, breast, and cervical cancer, than mentally healthy cancer patients, at a hazard ratio of 0.81. They also received significantly fewer radiotherapy and chemotherapy sessions than mentally healthy cancer patients.
Kisely et al conclude in the Archives of General Psychiatry: "This study suggests that although the cancer incidence in psychiatric patients is no higher than in the general population, psychiatric patients are more likely to have metastases at diagnosis and less likely to receive specialized interventions.
"This may explain the greater case fatality found in people with psychiatric disorder."
They add that the findings indicate a need for improved cancer screening and treatment among psychiatric patients.
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