Tumour-associated and non-tumour-associated microbiota in colorectal cancer

We read with interest the elegant study published by Flemer et al1 and commend the authors on their work. The authors provide convincing data to illustrate that faecal microbiota does not reflect accurately the underlying mucosal microbiota in patients with colorectal cancer (CRC).1 The authors also provide supporting evidence to illustrate that microbiota from sampled mucosa both on and off the cancer site is not significantly different. As previously demonstrated, they also provide corroboratory evidence to further conclude that microbiota is different in patients with CRC.

We are however concerned about the conclusions relating to the variability of mucosal microbiota based on tumour site. They present data to suggest that Faecalibacterium, Blautia and Clostridium were significantly more abundant in patients with proximal cancer. It is clear from established work that many environmental factors, including body mass index and diet (red meat), influence both mucosal and faecal microbiota.

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