Evaluation of antibiotic appropriateness at an outpatient oncology centre

Current evidence supporting antimicrobial stewardship programs focused largely in inpatient setting. With the shift in cancer management from inpatient to ambulatory setting, it is crucial to examine the prevalence and predictors of inappropriate antibiotics prescribing. This is a retrospective cross-sectional study conducted at the National Cancer Centre Singapore (NCCS). Patients at least 21 years, with an active or past cancer diagnosis and prescribed with at least one oral antibiotic by a NCCS physician from 1st July to 30th September 2019 were included. Antibiotic appropriateness was assessed using institutional antibiotic guidelines or published clinical practice guidelines. For cases where antibiotics appropriateness cannot be ascertained using these guidelines, an independent three-member expert panel was consulted. A total of 815 patients were screened; 411 (59.4% females) were included with mean age of 62.4 years. The top three cancer diagnoses were breast (26.5%), lung (15.6%) and head and neck (13.6%). More than half (58.6%) received appropriate antibiotic choice. Of which, 235 (97.5%), 238 (98.8%) and 194 (80.5%) received appropriate dose, frequency and duration respectively. The presence of non-oncologic immunosuppressive comorbidities (OR 4.890, 95% CI 1.556-15.369, p-value = 0.007), antibiotic allergy (OR 2.352, 95% CI 1.178-4.698, p-value = 0.015) and skin and soft tissue infections (OR 2.004, 95% CI 1.276-3.146, p-value = 0.003) were associated with a higher incidence of inappropriate antibiotic choice. This study highlighted that inappropriate antibiotic prescribing is prevalent in the ambulatory oncology setting. Predicators identified can aid in the design of targeted strategies to optimise antibiotic use in ambulatory oncology patients.