Risk–benefit balance of blood cultures among patients with stage IV cancer in unplanned admission: a nationwide propensity score–weighted study in Japan

Objectives Infection commonly causes unplanned admission in patients with stage IV cancer; however, the risk–benefit balance of blood cultures remains unclear. We evaluated clinical outcomes of blood culture among patients with stage IV cancer in unplanned admission. Methods We conducted a retrospective cohort study across Japan (April 2016 to March 2023). Patients with stage IV solid cancer receiving IV antimicrobials in unplanned admission were divided into blood culture (BC) and no blood culture (NC) groups. After overlap propensity score weighting, we compared mortality, functional disability, length of stay from antimicrobial initiation to discharge (LOS), and total hospitalization costs. Mortality risk was assessed using modified Poisson regression. Interaction tests were used to evaluate subgroup differences. Composite outcomes (mortality and functional disability) were assessed using a win-ratio approach (a hierarchical comparison of outcomes, prioritizing mortality over functional status). Results Among 10 915 patients (BC: 4029, NC: 6886), mortality was lower in the BC than the NC group (23.9% versus 29.2%; risk ratio: 0.81; 95% CI, 0.75–0.88). Mortality reduction was significantly greater in patients with prior chemotherapy or immunosuppressive agents. Composite outcomes were more favourable in the BC than the NC group (win ratio: 1.22; 95% CI, 1.13–1.32). However, BCs were associated with longer LOS (1.0 days; 95% CI, 0.0–1.9) and higher hospitalization costs (345.0 USD; 95% CI, 72.5–628.1). Conclusions BCs were associated with reduced mortality in patients with stage IV cancer, particularly those with immunosuppression. These findings may support personalized decision-making and resource allocation.