Clinical outcomes of ceftazidime/avibactam plus aztreonam in adult cancer patients with carbapenem-resistant Enterobacteriaceae (CRE) infections: a retrospective cohort study

Carbapenem‑resistant Enterobacteriaceae (CRE) infections represent a major therapeutic challenge in cancer patients due to limited antimicrobial options and the associated risk of poor clinical outcomes. This study aimed to evaluate the clinical and microbiological responses, safety, and mortality outcomes of ceftazidime/avibactam plus aztreonam combination therapy in adult cancer patients with CRE infections. This retrospective study was conducted at King Hussein Cancer Center, Jordan, and included adult cancer patients (≥ 18 years) who received ceftazidime/avibactam plus aztreonam for documented CRE infections between December-2022 and October-2024. Patient data were extracted from electronic medical records and included demographics, infection characteristics, microbiological results, treatment details, and clinical outcomes. The primary outcome was clinical and/or microbiological response. Secondary outcomes included 30‑day all‑cause mortality, CRE‑related infection mortality, and treatment‑related toxicities. Treatment success was defined as clinical and/or microbiological resolution without relapse, whereas treatment failure was defined as failure to achieve clinical or microbiological success, recurrence of infection within 30 days, or infection-attributable death. CRE‑related mortality was determined based on treating physician documentation. Descriptive statistics were used for data analysis. Thirty‑six patients were included, with females accounting for 58% ( n = 21) with median age of 53 years (IQR 35–62.25). Leukemia was the predominant malignancy (47%, n = 17), followed by solid tumors (33%, n = 12); five patients had undergone hematopoietic cell transplantation. The isolated CRE pathogens were Escherichia coli (67%, n = 24) and Klebsiella pneumoniae (33%, n = 12). Bloodstream infections were most common (81%, n = 29), followed by pneumonia (8%, n = 3), urinary tract infection (5%, n = 2), intra‑abdominal infection (3%, n = 1), and skin/soft tissue infection (3%, n = 1). All patients received at least one prior broad‑spectrum antimicrobial regimen, and 72% ( n = 26) received two or more prior lines before switching to the combination therapy. Median treatment duration was 10.4 days (IQR 7–13.25). Overall, treatment success occurred in 89% ( n = 32), whereas 11% ( n = 4) experienced treatment failure. Adverse events were limited to transient liver enzyme elevations in two patients and a mild rash in one patient. The 30-day all‑cause mortality rate was 25%, and CRE‑related mortality was 11%. Ceftazidime/avibactam plus aztreonam demonstrated high clinical and microbiological response rates and was well tolerated in cancer patients with CRE infections. Larger multicenter studies are needed to confirm these findings and improve generalizability.