Success of cancer immunotherapy reduced by antibiotics
Immunotherapy sits on the front line in a new wave of cancer research designed to help the body’s immune system more effectively target and kill deadly tumors. A new study from Imperial College London suggests antibiotic use prior to cancer immunotherapy can significantly reduce the efficacy of the treatment.
“Cancer immunotherapy can be successful in around 20 per cent of patients, but it’s very difficult to predict who is going to respond,” says corresponding author on the new research, David Pinato.
The new research followed nearly 200 patients undergoing checkpoint inhibitor therapy, a new kind of immunotherapy developed to stimulate the immune system into attacking tumors. Included were a number of different types of cancer, including non-small cell lung cancer, head and neck cancer, and melanoma.
The overall survival rate of all the patients studied was 14.6 months, but survival rates for patients receiving antibiotics up to 30 days before immunotherapy treatment was just two months. The negative effect was not seen when patients were given antibiotics alongside the immunotherapy treatment. This adds weight to a hypothesis offered by the researchers that antibiotics before immunotherapy can damage the gut microbiome and impact the body’s immune response.
A number of recent studies have found the immune system can be weakened by antibiotics, and particular research has revealed the efficacy of vaccines can be impaired by gut bacteria disruptions from antibiotic treatments. More specifically, two 2017 studies found certain gut bacteria either help or hinder checkpoint inhibitor treatments for cancer.
“This work adds further evidence that antibiotics have an impact,” says Pinato regarding the new Imperial research. “We have shown that with prior antibiotic exposure, patients’ response to immunotherapy and survival crashes.”
This new study is admittedly very small, and the researchers are clear they cannot account for any other health conditions that may be affecting survival rates in their particular cohort. The new research also did not directly analyze patients' gut microbiomes so the final conclusion cannot be causally linked to microbiome disruptions.
Nevertheless, there is a strong body of evidence to link impaired immune responses to microbiome disruptions associated with antibiotic use. And it is very reasonable to hypothesize any treatment relying on activating an immune response will be affected by mechanisms known to lower immune activity.
Despite these strong findings, more work is needed to better understand how antibiotic use is influencing the microbiome, and whether bacterial augmentation can improve patient responses to immunotherapy treatments. Pinato does stress that this research should not cause patients to refuse antibiotics when they are needed.
“It is important that patients who need antibiotics to treat bacterial infections receive the drugs they need,” says Pinato. “But these findings urge for more care in the decision-making process for some patients. It raises questions of whether we need a higher threshold for antibiotic prescribing in cancer patients due to receive immunotherapy.”
The new research was published in the journal JAMA Oncology.
Source: Imperial College London