Antibiotic ‘link to bowel cancer precursor’

People who take antibiotics for a long time are more likely to develop growths on the bowel which can be a precursor to cancer, a study suggests.  Researchers say this adds to emerging evidence that the diversity of bugs in the gut could have role in the development of tumours.  Their paper appears in the journal Gut. But experts warn that the early results need further investigation and say people should not stop taking antibiotics.  Bowel polyps – small growths on the lining of bowel – are common, affecting 15%-20% of the UK population.  In most cases, they do not cause any symptoms and do not become cancerous but some go on to develop into cancers if left untreated.  In this study, researchers looked at data from 16,600 nurses who were taking part in a long-term US trial called the Nurses’ Health Study. They found that nurses who had taken antibiotics for two months or more, between the ages of 20 and 39, were more likely to be diagnosed with particular types of bowel polyps – known as adenomas – in later life, compared with people who had not taken long-term antibiotics in their 20s and 30s.  And women who had taken antibiotics for two months or more in their 40s and 50s were even more likely to be diagnosed with an adenoma decades later. But the study does not look at how many polyps went on to become cancerous.
The authors say their research cannot prove that antibiotics lead to the development of cancer and acknowledge that the bacteria which the drugs are deployed to treat might also play an important role.  But they say there is a “plausible biological explanation” for the patterns seen.  Writing in the journal they said: “Antibiotics fundamentally alter the gut microbiome, by curbing the diversity and number of bacteria, and reducing the resistance to hostile bugs.” “This might all have a crucial role in the development of bowel cancer, added to which the bugs that require antibiotics may induce inflammation, which is a known risk for the development of bowel cancer.” They added: “The findings if confirmed by other studies, suggest the potential need to limit the use of antibiotics and sources of inflammation that may drive tumour formation.” Meanwhile, Dr Sheena Cruickshank, am immunology expert at the University of Manchester, said anything that disturbs our gut bacteria, such as changes in diet, inflammation or antibiotic use, could potentially have an impact on our health. But she said it was difficult to tease out whether other factors – like diet – could be more deeply involved in the current study.

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