Burden and clinical outcomes of hospital-coded infections in patients with cancer: an 11-year longitudinal cohort study at an Australian cancer centre.

Patients with cancer are at increased risk for infection, but the relative morbidity and mortality of all infections is not well understood. The objectives of this study were to determine the prevalence, incidence, time-trends and risk of mortality of infections associated with hospital admissions in patients with haematological- and solid-tumour malignancies over 11 years. A retrospective, longitudinal cohort study of inpatient admissions between 1 January 2007 and 31 December 2017 at the Peter MacCallum Cancer Centre was conducted using administratively coded and patient demographics data. Descriptive analyses, autoregressive integrated moving average, Kaplan-Meier and Cox regression modelling were applied. Of 45,116 inpatient hospitalisations consisting of 3033 haematological malignancy (HM), 18,372 solid tumour neoplasm (STN) patients and 953 autologous haematopoietic stem cell transplantation recipients, 67%, 29% and 88% were coded with ≥ 1 infection, respectively. Gastrointestinal tract and bloodstream infections were observed with the highest incidence, and bloodstream infection rates increased significantly over time in both HM- and STN-cohorts. Inpatient length of stay was significantly higher in exposed patients with coded infection compared to unexposed in HM- and STN-cohorts (22 versus 4 days [p < 0.001] and 15 versus 4 days [p < 0.001], respectively). Risk of in-hospital mortality was higher in exposed than unexposed patients in the STN-cohort (adjusted hazard ratio [aHR] 1.61 [95% CI 1.41-1.83]; p < 0.001)) and HM-cohort (aHR 1.30 [95% CI 0.90-1.90]; p = 0.166). Infection burden among cancer patients is substantial and findings reflect the need for targeted surveillance in high-risk patient groups (e.g. haematological malignancy), in whom enhanced monitoring may be required to support infection prevention strategies.