Prior antibiotic use may be associated with a reduced treatment response to checkpoint inhibitors, and worse outcomes, in patients with cancer, according to investigators.
In a prospective cohort study, researchers followed 196 patients with cancer who were treated with immune checkpoint inhibitors in routine clinical practice.
A total of 22 patients had been treated with a 7-day or less course of broad-spectrum beta-lactam–based antibiotics in the 30 days prior to starting immune checkpoint inhibitor therapy, and 68 patients were concurrently taking broad-spectrum beta-lactam–based antibiotics with their checkpoint inhibitor therapy.
The analysis revealed that prior antibiotic therapy was associated with nearly a 100% greater likelihood of poor response to checkpoint inhibitor therapy (P less than .001) and significantly worse overall survival (2 vs. 26 months). Patients who had been on prior antibiotic therapy were also more likely to stop checkpoint inhibitor therapy because their disease had progressed, and were more likely to die of progressive disease while on checkpoint inhibitors.
However, concurrent antibiotic use did not appear to affect either treatment response to checkpoint inhibitors or overall survival.
The most common indication for both prior and concurrent antibiotic use was respiratory tract infections. Researchers examined whether cancer type might play a role in contributing to the association; for example, chronic airway disease in lung cancer might mean higher likelihood of antibiotic use but also lower treatment response and survival.
They found that the association between prior antibiotic therapy and overall survival was consistent across the 119 patients with non–small cell lung cancer, the 38 patients with melanoma, and the 39 patients with other tumor types.
The association was also independent of the class of antibiotic used, the patient’s performance status, and their corticosteroid use.
“Broad-spectrum ATB [antibiotic] use can cause prolonged disruption of the gut ecosystem and impair the effectiveness of the cytotoxic T-cell response against cancer, strengthening the biologic plausibility underlying the adverse effect of ATB therapy on immunotherapy outcomes,” wrote Dr. David J. Pinato, from Imperial College London, and coauthors in JAMA Oncology.
Addressing the question of whether comorbidities might be the mediating factor, the authors pointed out that the use of antibiotics during checkpoint inhibitor therapy – which was a potential indicator of patients’ status worsening during treatment – was not associated with reduced response to treatment or lower overall survival.
“Although provision of cATB [concurrent antibiotic] therapy appears to be safe in the context of immunotherapy, clinicians should carefully weigh the pros and cons of prescribing broad-spectrum ATBs prior to ICI [immune checkpoint inhibitor] treatment,” they wrote.
The study was supported by the Imperial College National Institute for Health Research Biomedical Research Centre, the Imperial College Tissue Bank, the Imperial Cancer Research U.K. Centre, the National Institute for Health Research, and the Wellcome Trust Strategic Fund. Two authors reported receiving grant funding and personal fees from the pharmaceutical sector unrelated to the study.
SOURCE: Pinato D et al. JAMA Oncol. 2019 Sep 12. doi: 10.1001/jamaoncol.2019.2785.