Negative Effect of Intravenous Antibiotics on Survival in Patients with Triple-Negative Breast Cancer.

Background: The anti-tumor response of the immune system is pivotal for treating triple-negative breast cancer (TNBC), particularly as targeted therapies are limited. However, the impact of immune-modulating factors such as the application of granulocyte-stimulating factors (G-CSFs) or infections, including febrile neutropenia, prophylactic or therapeutical application of oral antibiotics (OABs), and the need for intravenous antibiotics (IABs), on survival outcomes remains unclear.

Methods: 1583 patients with early-stage TNBC enrolled in the SUCCESS A or C study underwent primary surgery, adjuvant chemotherapy, and radiotherapy if indicated. All patients had Eastern Cooperative Oncology Group (ECOG) status ≤ 2. The effects of G-CSF, OAB, and IAB application on overall survival (OS), invasive disease-free survival (iDFS), breast cancer-specific survival (BCSS), and distant disease-free survival (DDFS) were assessed.

Results: Only IAB treatment was significantly associated with decreased survival in univariable analyses (OS: p = 0.003; iDFS: p = 0.036; BCSS: p = 0.011; DDFS: p = 0.044), while G-CSF and OAB administration were not. Adjusted multivariable Cox regressions including febrile neutropenia and dose reduction/shift, ECOG, age of patients, and other clinicopathological parameters confirmed a significant negative effect of IABs on OS (p = 0.020), BCSS (p = 0.018), and DDFS (p = 0.044).

Conclusions: In summary, IABs during adjuvant chemotherapy seems to be a risk factor for inferior OS, BCSS, and DDFS in TNBC patients, possibly by affecting microbiome-related immune response modulation. Hence, preventive measures to avoid the need for IABs should be considered in these patients.