Gut Microbiome Affects How You Respond to Cancer Treatment


Cancer immunotherapies command the body’s immune system to destroy cancer cells, but the bacteria living in patient’s guts can affect the outcome of such therapies according to two new research studies.


The studies, published in the journal Science, add to a growing body of evidence showing how the microorganisms living in and on our bodies (collectively called the microbiome) can affect every aspect of our health.


The studies also show that antibiotics can hamper the effectiveness of some cancer immunotherapies.


In particular, the researchers found that patients receiving antibiotics to treat infections were less responsive to cancer therapies targeting the related proteins PD-1 and PD-L1.


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Researchers analyzed fecal samples from over 100 patients with advanced melanoma before they started taking anti-PD1 immunotherapy drugs. They found that people with the most diverse gut microbiomes were more likely to respond to the treatment.


Patients’ responsiveness to treatment was also linked to the types of bacteria in their guts.


People whose microbiomes contained lots of bacteria from a group called Clostridiales were more likely to respond to treatment, whereas patients with gut microbiomes containing lots of bacteria belonging to a group called Bacteroidales were less likely to respond.


Although it is too soon for doctors to change how they use antibiotics in cancer patients, the work is a big leap forward over previous studies that have mostly relied on mouse models.


The next key problem is figuring out what the different types of bacteria are actually doing to affect these cancer therapies. 



Gopalakrishnan, V. et al. Science (2017).

Routy, B. et al. Science (2017).