Unplanned health service utilisation among people living with cancer and mental health conditions: A retrospective matched case-comparison study in Australia.

BACKGROUND: Mental health conditions are associated with inequities across the cancer pathway, yet differences in unplanned health service use remain poorly described. This study examined sociodemographic, clinical and virtual care use factors associated with unplanned health service use among adults living with cancer, with and without mental health conditions. METHODS: A retrospective matched case-comparison study was conducted using linked data from three Australian states. Adults aged ⩾ 18 years with cancer were included if they had an outpatient oncology visit between 2018 and 2021 and had either an inpatient or ambulatory mental health encounter. Individuals with mental health conditions were matched 1:1 to individuals without using propensity scores. Adjusted negative binomial models estimated incidence rate ratios for unplanned emergency department use, low-acuity emergency department use, unplanned hospitalisations and cancer-related hospitalisations within 12 months. RESULTS: Among 99,230 adults with cancer, 9925 (10%) had a recorded mental health condition. After matching, individuals with mental health conditions had higher rates of unplanned emergency department use (incidence rate ratio = 1.34, 95% confidence interval = [1.30-1.39]), low-acuity emergency department use (incidence rate ratio = 1.26, 95% confidence interval = [1.18-1.34]), unplanned hospitalisations (incidence rate ratio = 1.32, 95% confidence interval = [1.28-1.37]) and cancer-related hospitalisations (incidence rate ratio = 1.48, 95% confidence interval = [1.41-1.55]) than those without. Virtual care use, digestive and lung cancers (vs breast), and ⩾ 1 Charlson comorbidity were also associated with increased unplanned use. CONCLUSIONS: Coexisting mental health conditions are linked to greater unplanned service use among people with cancer. Integrating mental health support into oncology care and coordinated models may reduce disparities. Further research should clarify the role of virtual care in this population.