Alcohol increases bowel cancer risk across major tumour subtypes

Research funded by Wereld Kanker Onderzoek Fonds (WKOF), as part of the World Cancer Research Fund International grant programme, has produced evidence strengthening the case that higher alcohol intake increases bowel (colorectal) cancer risk across its different tumour subtypes. It is the largest ever study on that topic.

It is already well known that drinking alcohol increases the risk of bowel cancer, but the mechanisms needed to be better understood.

Now, the researchers led by Dr Christos Chalitsios and Dr Konstantinos Tsilidis at the University of Ioannina (Greece) and Imperial College London (UK) and the University of Ioannina (Greece), working with international consortia, have brought clearer answers to one of the most important long-standing questions: when alcohol increases bowel cancer risk, does it do so mainly through particular “molecular pathways” of the disease, or broadly across them all?

Looking across cancer pathways

To investigate this, researchers pooled data from large consortia (GECCO and the Colon Cancer Family Registry), analysing more than 22,000 people (11,826 cases and 10,888 controls).

Because bowel cancers aren’t all the same, the team examined tumour subtypes defined by molecular features including microsatellite instability (MSI), CpG island methylator phenotype (CIMP), and mutations in the BRAF and KRAS genes.

The key finding was that the alcohol–cancer association looked broadly similar across MSI, CIMP, BRAF and KRAS tumour subtypes (and in combined “pathway” groupings).

In other words, the study found no convincing evidence that alcohol preferentially drives one major molecular subtype over another.

Higher intake, higher risk

Among people who drink alcohol, risk increased with higher intake: each additional 14 g/day (about 1 drink/day) was linked with around a 10% higher colorectal cancer risk, and this pattern was mainly driven by heavier drinking (more than 28 g/day, roughly more than 2 drinks/day).

Genetic analyses further supported a link between higher alcohol consumption and higher overall colorectal cancer risk, and again did not suggest that risk is confined to any single subtype.

What this means for cancer prevention is clear. Heavier drinking appears to increase bowel cancer risk regardless of tumour subtype. Therefore, our recommendation for cancer prevention continues to be to avoid alcohol. If you do drink, cutting down can help reduce your risk, because there is no completely safe level of alcohol intake when it comes to cancer.

Dr Tsilidis explained:

“Alcohol is consistently associated with a range of adverse health outcomes, and contemporary evidence no longer supports the idea that it is “good” for health at any level. Although there are still unknowns in alcohol and health research, alcohol should not be recommended for disease prevention, and people who choose to drink are advised to keep consumption as low as possible.”