In patients with naïve advanced non-small cell lung cancer (NSCLC) and high PD-LI expression who are treated with pembrolizumab, the use of intravenous (IV) antibiotics may negatively impact progression free survival (PFS) and overall survival, according to research presented at the IASLC 2019 World Conference on Lung Cancer.

To evaluate the effect of antibiotics on survival outcomes in patients starting treatment with immune checkpoint inhibitors, researchers conducted a retrospective study that included patients with advanced NSCLC with high PD-L1 expression that were treated with pembrolizumab monotherapy. Patients who were administered antibiotics 2 months prior to or within the first month after starting pembrolizumab were included in the analysis.

Between September 2016 and March 2019, 121 patients were identified across 12 hospitals in Spain. “Patients who received [antibiotics] had more risk of disease progression as best response (52.2% vs 24.5%, risk ratio: 2.1, 95% CI, 1.2 to 3.7, P=.007),” the researchers reported. In addition, treatment with antibiotics was associated with shorter overall survival (HR 1.9, 95%CI: 1.1-3.7, P=.047) and shorter PFS (HR 2.6, 95% CI, 1.4 to 4.8, P=.002). 

When comparing route of administration, patients who received IV antibiotics had shorter overall survival (HR 3.5, 95% CI, 1.2 to 10.3, P=.025) and shorter PFS (HR 2.2, 95% CI, 1 to 4.8, P=.05) than those who received oral antibiotics. Differences in PFS and overall survival were noted when comparing IV antibiotic use to no use, however no differences were observed between those who received oral antibiotics and those who did not. The researchers also noted that antibiotic type did not impact survival outcomes.  

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“To our knowledge, this is the first retrospective study evaluating the impact of [antibiotics] on the efficacy of [immune checkpoint inhibitors] in first-line treatment setting of NSCLC patients,” the researchers concluded, adding that “results suggest that use of intravenous [antibiotic] has a negative impact on disease control rate and survival outcomes.”

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Rubio, X. Mielgo, et al. Early antibiotic use affects the efficacy of first line immunotherapy in lung cancer patients but route of administration seems to be decisive. Presented at: The IASLC 2019 World Conference on Lung Cancer (WCLC) of the International Association for the Study of Lung Cancer; September 7-10, 2019; Barcelona Spain. Abstract P1.04-16.