A new retrospective analysis suggests that immunotherapy may be less effective in patients who receive antibiotics less than a month before starting treatment.

In the study, cancer worsened more quickly in such patients than in those who did not receive antibiotics (median progression-free survival 2.3 months vs. 8.1 months).

The study was presented at the 2017 Genitourinary Cancers Symposium in Orlando.

An estimated 64,000 people will be diagnosed with kidney cancer in 2017 in the United States, and more than 14,400 will die of the disease.

The rates of kidney cancer have been steadily rising over the last decade. Renal cell carcinoma is the most common type of adult kidney cancer, making up about 85% of diagnoses.

According to the authors, this study is the first to analyse the impact of antibiotics on immune checkpoint inhibitors and provides the first evidence of a relationship between the gut microbiome (microbes residing in the gut) and patients’ response to immunotherapy.

The researchers believe that the negative effect of antibiotics is due to the antibiotics wiping out the “good bacteria” in the gut. Earlier, research in mice suggested that certain microorganisms dwelling in the gut interact with the immune system in a way that seems to help immune checkpoint inhibitors work better.

“These early findings show that doctors prescribing cancer immunotherapy should pay closer attention to antibiotic use,” said lead study author Lisa Derosa, MD, a PhD candidate at the Gustave Roussy Cancer Institute, Paris-Sud University in Villejuif, France. “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.”

The analysis included 80 patients with metastatic renal cell carcinoma who were enrolled in prospective clinical trials of immune checkpoint inhibitors.

The patients were treated with single-agent PD-1 or PD-L1 inhibitors, combinations of PD-1 inhibitors and CTLA-4 inhibitor or combinations of PD-L1 inhibitor and bevacizumab.

Overall, 16 patients had been treated with broad-spectrum antibiotics (antibiotics that work against a wide range of bacteria) up to one month before receiving the first dose of immunotherapy. 

Cancer worsened faster in patients who had received antibiotics, regardless of factors such as patient age, gender and tumour characteristics.

According to the authors, there is preliminary indication that overall survival may also be shorter with antibiotic use, but longer follow up is needed to reach a definitive conclusion.

The researchers plan to enroll additional patients in this study.

At the same time, they will continue studies in mice to try to pinpoint the types of gut bacteria that affect response to immune checkpoint inhibitors and the kinds of antibiotics that have the greatest impact on outcomes.

Meanwhile, other ongoing studies in kidney and lung cancers are exploring the connection between antibiotic use and outcomes with cancer immunotherapy.

Source: ASCO GU