Background Febrile neutropenia is a common complication of chemotherapy-induced neutropenia and neutropenia related to the disease. It occurs in 80% of patients with hematological malignancies with a significant impact on morbidity and mortality. The issue of antibiotic treatment duration in febrile neutropenia is unresolved. The rationale for continuing antibiotics until neutrophil recovery is based on the concern that neutropenic patients may have an ongoing risk of life-threatening infection, and neutropenia may conceal classical manifestations of infection. On the other hand, prolonged broad-spectrum antibiotic treatment has been associated with the emergence of antibiotic resistance, Clostridioides difficile infection and invasive fungal infections, as well as adverse effects and allergic reactions. The evidence suggesting the beneficial effects of prolonged antibiotic treatment is derived from 2 small randomized controlled trials (RCTs) from the 1970s, which showed an increase in infections and mortality with early stoppage of antibiotics. Two recently done RCTs, the HOW LONG and the SHORT studies, suggested that early discontinuation of antibiotics is feasible and is not associated with adverse outcomes. However, the first was not powered for safety outcomes and the second included a lower-risk population and a de-escalation strategy. Despite these reassuring studies, most centres still utilize the resolution of neutropenia as one of the criteria for stopping antibiotics in patients with febrile neutropenia.

Objective This pilot RCT will assess the feasibility of conducting a full future RCT. In the full trial, the investigators will compare early antibiotic discontinuation to the continuation of antibiotics until the resolution of neutropenia in high-risk febrile neutropenic patients, aiming to prove non-inferiority.

Methods The investigators will conduct a pilot open-label, multicentre RCT involving centres in Canada and Israel. The investigators will include adult patients with acute leukemia or patients undergoing allogeneic hematopoietic stem-cell transplantation diagnosed with febrile neutropenia of unknown source. Patients who have received antibiotics for at least 72 hours and are still neutropenic will be recruited if afebrile for at least 24 hours. Patients will be randomized to either early discontinuation or prolonged treatment in a 1:1 ratio using stratified, permuted block randomization. Patients randomized to the intervention arm will have antibiotics stopped at randomization, whereas those in the control group will receive antibiotics until resolution of neutropenia. The outcomes for this pilot study will be to assess the recruitment rate and understand the barriers to obtaining physician and patient consent; assess adherence to the allocated intervention and understand the reasons for crossovers; and measure primary outcome data for sample size re-estimation. This trial will serve as an internal pilot and the outcome data generated will contribute to the full trial. The primary outcome of the full trial will be a composite of all-cause mortality, transfer to intensive care units, or any clinically or microbiologically documented infection.