Patients with cancer who receive antibiotics within a month before beginning their immunotherapy treatment may find the efficacy of their treatment reduced, according to a study that will be presented at the Genitourinary Cancers Symposium (Orlando, FL, February 18, 2017; Abstract 462).
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Researchers led by Lisa Derosa, MD, Gustave Roussy Cancer Institute, Paris-Sud University (France), conducted a study to compare the effects of immunotherapy with checkpoint inhibitors in patients with metastatic renal cell carcinoma who either received or did not receive broad-spectrum antibiotics prior to therapy. A total of 80 patients were sampled from various prospective clinical trials, 16 of whom received antibiotics prior to immunotherapy. Patients were treated either with single-agent PD-1 or PD-L1 inhibitors, combinations of a PD-1 inhibitor and a CTLA-4 inhibitor, or combinations of a PD-L1 inhibitor and bevacizumab.
Results of the study showed disease progressed more quickly in the patients who received antibiotics compared with those who did not (median progression-free survival [PFS], 2.3 vs 8.1 months; P < .001). The trend towards decreased survival remained after researchers adjusted for multiple prognostic risk factors, including age, risk group, and tumor burden.
Authors of the study noted that the data are not yet ready for clinical application. Further prospective studies are needed to validate the negative effects on PFS as a result of prior antibiotics.
Additionally, authors noted that the study provides further evidence of a relationship between bacteria in the gut and patients’ response to immunotherapy. Previous studies in mice have shown that the bacterial composition of the gut could impact the effectiveness of both PD-1 and CTLA-4 inhibitors. Other studies have shown responses to immunotherapy are better in those patients who have a greater diversity of bacteria in their microbiome.
Dr Derosa indicated that further studies are warranted to investigate whether alteration of microbiome compositions is responsible for a negative effect of antibiotics on immunotherapy responses. Nonetheless, she maintains the significance of the study and suggests that its implications may extend to many cancer types.
"This research may be relevant to more than just kidney cancers, as antibiotics are commonly prescribed to patients with cancer to prevent or treat infections related to cancer treatment or weakened immune system," Dr Derosa told Medscape News.
