Cancer patients given broad-spectrum antibiotics up to a month before starting immune checkpoint inhibitor therapy have greatly reduced chances of survival, a study suggests.

An association between prior antibiotic use and poor response to immune checkpoint inhibitor (ICI) therapy persists regardless of tumour site and the class of antibiotic used, the UK researchers say.

In an observational study published in JAMA Oncology, the researchers followed 196 patients with cancer, (median age 68) who underwent ICI therapy between 2015 and 2018, to investigate the impact of antibiotics on their response.

Most patients (119) in the cohort had non-small cell lung cancer, 38 had melanoma, and 39 had other tumour types. The average duration of ICI therapy was 3.3 months.