Gut microbiome alterations predictive of cancer risk

Cancer is the second leading cause of death worldwide. A large proportion of cancer deaths is associated with modifiable risk factors, such as tobacco use, or dietary factors. This indicates a major role for prevention to reduce cancer deaths. Prevention has two main facets, identifying individuals at risk and mitigating their risk. Here we focus on the first, using microbiome alterations to stratify individuals into groups of higher and lower cancer risk, leveraging two cohorts of cancer patients and four general population cohorts from different European countries, totaling 16,255 individuals and including 3,341 cancer cases. For that, we first establish existence of common microbiome alterations in several specific cancer types (lung, kidney and breast) and show their presence in groups of individuals with different cancers. These alterations are found in France, the Netherlands, Finland and Latvia. Next, we show that people who are diagnosed with cancer after microbiome sampling, totaling 1,640 individuals, have microbiome alterations like those found in diagnosed cancer cases, albeit to a lower degree, across the four populations studied, indicating that the microbiome may evolve towards the one found in cancer well before cancer is diagnosed. Finally, we show that the extent of microbiome alterations can be used for stratification of both the diagnosed cancer cases and people who may be at increased cancer risk.