Unplanned cancer presentation in patients with psychiatric disorders: A nationwide register-based cohort study in Denmark

1 Background

Cancer is one of the leading causes of death worldwide [1] . Despite improvements in diagnostics and treatment in recent years [23] , the cancer survival remains excessively poor in some patient groups. The prognosis after cancer is worse in patients with pre-existing psychiatric disease than in patients without, although the difference seems to vary with psychiatric disease 4567 . The reason for this disparity is likely to be multifaceted [5] , with one of the proposed reasons being suboptimal diagnosis and treatment of cancer in patients with pre-existing psychiatric disorders [89] . Yet, more research has been called for on the diagnostic process of cancer in patients with psychiatric disorders [58] .

The route to cancer diagnosis (RtD) has been linked with the prognosis after cancer. Studies have found more favourable prognosis across different cancer types when the route to diagnosis begins in primary care, particularly among patients referred urgently through the two-week-wait (TWW) route in the UK or through cancer patient pathway (CPP) routes in Scandinavia 101112 . The worst prognosis is seen in patients presenting through an emergency route, which is only partly explained by advanced disease stage at diagnosis 131415 . In the literature, the compound term “emergency presentation” is most often used, but “unplanned admission” or “acute presentation” are also sometimes used. These terms cover the same concept, although with some variation in their definitions (depending on methodological approach and available data). In this study, we use the term “unplanned presentation” to broadly cover pathways that are acute and unplanned pathways that are not emergencies.

In patients with pre-existing psychiatric disorders, the cancer pathway has been linked with underdetection, delayed diagnosis and lower screening uptake [516171819 . Recently, our research group published a study on the route to diagnosis among cancer patients with psychiatric disorders and found a higher likelihood of unplanned presentation for patients with psychiatric disorders compared to those without [20] . International research indicates that unplanned presentation in general are more likely in patients with comorbidities, lower socioeconomic status, ethnic minorities or among older patients [10212223 . No such evidence exists for patients with existing psychiatric disorders, yet a deeper understanding of sociodemographic differences in cancer diagnostics is important when designing interventions aiming at cancer presentation through unplanned routes [13] . Hence, this study focus on cancer patients with pre-existing psychiatric disorders and aims to estimate the association between patient characteristics (including social characteristics and coexisting physical morbidity) and cancer diagnosis after an unplanned presentation. We hypothesised that vulnerable patient groups, i.e. patients with high age, low education and low income, being single, having high comorbidity and being non-attenders in primary care, would be more likely to be diagnosed with cancer through an unplanned presentation. We also expected these associations to vary among subgroups of patients with different psychiatric disorders.