A small, but significant, association between alcohol consumption and non-melanoma skin cancers has been found in a new systematic review. The most common of these types of cancer are squamous cell and basal cell carcinoma.
Although the news is obviously a cause for concern, non-melanoma skin cancers are far less aggressive than malignant melanoma, a type of skin cancer that can spread to other parts of the body. With prompt diagnosis and treatment, non-melanoma skin cancers are often curable.
The study was carried out by researchers from Chan School of Public Health in Boston and other institutions in the US, Taiwan and South Africa.
The review gathered the results from 13 studies and found that 10g of alcohol per day was linked with a 7% increase in risk of basal cell and 11% increase in risk of squamous cell carcinoma. 10g of alcohol per day is equivalent to one unit of alcohol, such as a glass of wine.
However, these findings come with several caveats. The individual studies differed in terms of the alcohol categories they compared and whether they took account of the various factors that may influence the links.
Even if alcohol does have a direct effect, these are relatively small risk increases. For example, if a person had a 10% lifetime risk of a squamous cell cancer, an 11% risk increase would only increase this risk to 11%.
People drinking responsibly within current alcohol recommendations (no more than 14 units a week for men and women, spread over at least three days) should not be concerned.
The review aimed to pool the available literature looking at the link between alcohol intake and risk of non-melanoma skin cancer. This includes squamous cell and basal cell carcinoma, which are slower growing and less aggressive than malignant melanoma.
Like melanoma, ultraviolet (UV) light is a risk factor for developing these cancers, though dietary and alcohol links have also been suggested.
A systematic review is the best way of gathering the evidence to date, though the results are only as good as the size and quality of the underlying studies.
For basal cell carcinoma, six studies were pooled, which found that every extra 10g of ethanol consumed per day (a small glass of wine) was linked with a 7% increase in risk of this type of cancer (relative risk 1.07, 95% confidence interval 1.04 to 1.09). However, the peak for risk was only 9g of alcohol per day, with little increase in risk above that amount.
There was considerable variation in the results of the individual studies. The positive result mainly came from the three US studies, with the two European studies and single Australian study in this group finding no statistically significant link.
For squamous cell carcinoma, only three studies were pooled. A 10g increase in ethanol consumption per day was linked with an 11% increase in risk of this type of cancer (relative risk 1.11, 95% confidence interval 1.06 to 1.16).
There was minimal difference in the results of the three studies.
The researchers conclude that their study:
“found evidence that alcohol drinking is positively associated with both [basal cell] and [squamous cell] carcinoma risk in a dose-dependent manner. These results should be interpreted with caution due to potential residual confounding. Nonetheless, because alcohol drinking is a prevalent and modifiable behaviour, it could serve as an important public health target to reduce the global health burden of [non-melanoma skin cancer].”
These findings should be interpreted with care before concluding that an alcoholic drink per day increases your risk of skin cancer.
There are several important cautions:
These are only observational studies. It wouldn’t be possible to randomise people to different alcohol intake and follow them to look at cancer development. And with observational studies, many other health, socio-demographic and lifestyle factors may be influencing the link between alcohol intake and cancer development. The studies differed considerably in terms of the influencing factors they took account of, with some adjusting for various confounders, some adjusting for only age and gender, and some taking none into account. Therefore we cannot be sure that alcohol is having a direct and independent effect on cancer risk.
The individual studies differed in the alcohol intake they compared. For example, some compared all drinkers with non-drinkers, others compared intake of more or less than one glass a week, and others compared “above average” intake with none. This makes it very difficult when pooling the studies to be sure what intakes you are comparing – especially given the additional limitation that alcohol intake will have been self-reported, so may be inaccurate.
The relative risk increases are very small at only 7% and 11%. We don’t know from this paper what the absolute risk of these cancers was – in other words, what proportion of all people actually developed these cancers during the follow-up time. A small increase in a small risk still results in a small risk. For example, if a person had a 10% baseline risk of squamous cell carcinoma, an 11% relative risk increase would only raise that baseline risk to 11%.
Overall, this study provides a good summary of the available literature on the links between alcohol intake and non-melanoma skin cancer, but we can’t be certain of the size and strength of these links.
People drinking responsibly within current alcohol recommendations should not be concerned.