Effect of antibiotic drug use on outcome and therapy-related toxicity in patients with glioblastoma-A retrospective cohort study.

Background: Glioblastoma (GB) is the most frequent malignant brain tumor and has a dismal prognosis. In other cancers, antibiotic use has been associated with severity of chemotherapy-induced toxicity and outcome. We investigated if these mechanisms are also involved in GB.

Methods: We selected a cohort of 78 GB patients who received combined radiochemotherapy. We investigated if exposure to prediagnostic antibiotic use is associated with clinical side effects and laboratory changes during adjuvant therapy as well as overall survival (OS) and progression-free survival (PFS) using chi-square test, binary logistic regression, Kaplan-Meyer analysis, and multivariable Cox regression.

Results: Seventeen patients (21.8%) received at least one course of prediagnostic antibiotics and 61 (78.2%) received no antibiotics. We found a higher incidence of loss of appetite (23.5% vs. 4.9%; P = .018) and myelosuppression (41.2% vs. 18.0%; P = .045) in the antibiotic group. Multivariable logistic regression analysis revealed antibiotics to be a predictor for nausea (OR = 6.94, 95% CI: 1.09-44.30; P = .041) and myelosuppression (OR = 9.75, 95% CI: 1.55-61.18; P = .015). Furthermore, lymphocytopenia was more frequent in the antibiotic group (90.0% vs. 56.1%, P = .033). There were no significant differences in OS (P = .404) and PFS (P = .844). Multivariable Cox regression showed a trend toward shorter survival time (P = .089) in the antibiotic group.

Conclusions: Our study suggests that antibiotic use affects symptoms and lab values in GB patients. Larger prospective studies are required to investigate if prediagnostic antibiotic use could be a prognostic factor in GB patients.