Context There is a 30% higher case fatality rate from cancer in psychiatric patients even though their incidence of cancer is no greater than in the general population. The reasons are unclear, but if increased cancer mortality were due to lifestyle only, cancer incidence should be similarly increased. Other hypotheses include delays in presentation, leading to more advanced staging at diagnosis, and difficulties in treatment access following diagnosis.
Objective To assess why psychiatric patients are no more likely than the general population to develop cancer but are more likely to die of it.
Design, Setting, and Patients A population-based record-linkage analysis compared psychiatric patients with the Western Australian population, using an inception cohort to calculate rates and hazard ratios. Mental health records were linked with cancer registrations and death records from January 1, 1988, to December 31, 2007, in Western Australia.
Main Outcome Measures Metastases, incidence, mortality, and access to cancer interventions.
Results There were 6586 new cancers in psychiatric patients. Cancer incidence was lower in psychiatric patients than in the general population in both males (rate ratio = 0.86; 95% CI, 0.82-0.90) and females (rate ratio = 0.92; 95% CI, 0.88-0.96), although mortality was higher (males: rate ratio = 1.52; 95% CI, 1.45-1.60; females: rate ratio = 1.29; 95% CI, 1.22-1.36). The proportion of cancer with metastases at presentation was significantly higher in psychiatric patients (7.1%; 95% CI, 6.5%-7.8%) than in the general population (6.1%; 95% CI, 6.0%-6.2%). Psychiatric patients had a reduced likelihood of surgery (hazard ratio = 0.81; 95% CI, 0.76-0.86), especially resection of colorectal, breast, and cervical cancers. They also received significantly less radiotherapy for breast, colorectal, and uterine cancers and fewer chemotherapy sessions.
Conclusions Although incidence 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 their greater case fatality and highlights the need for improved cancer screening and detection.