Alcohol and cancer
Published: 18 November 2017
The Nov 7 publication of Alcohol and Cancer: a Statement of the American Society of Clinical Oncology
(ASCO) emphasises the prominence of alcohol as a proven cause of many
cancers. This view is not novel and comes exactly 30 years after a
working group of the International Agency for Research on Cancer
determined that alcoholic beverages were carcinogenic to humans. It has
been echoed by other cancer societies since then but seemingly ignored
by the wider medical community and by society. The influential
endorsement by ASCO provides a powerful impetus to act on decades of
evidence that alcohol harms health.
Alcohol is causally
linked to upper aerodigestive tract cancers (oral cavity, pharynx,
larynx, oesophagus) and those of the colon, liver, and female breast.
Associations exist for many other types of cancer, but the precise role
of alcohol requires further research to be fully disentangled from
ecological and lifestyle factors. Historical assertions of benefit from
alcohol are likely misinterpreted or exaggerated, because no lower
threshold for cancer risk has yet been identified.
Carcinogenesis is
most common in tissues that are in direct contact with alcohol and
increases with exposure. For example, a three times increase in the
recommended alcohol limit raises the risk of oesophageal cancer eight
times, leading to estimates that three-quarters of oesophageal cancers
are due to high alcohol consumption. Because cancer of the oesophagus
has a 5-year survival rate of less than 10%, prevention is paramount.
Although
the mechanism of carcinogenesis might vary by the type of tissue
involved, it is consistent for different forms of alcohol and likely
involves ethanol's genotoxic metabolite, acetaldehyde. Additional
evidence comes from east Asian populations, in which variant genotypes
that impair aldehyde dehydrogenase are common (thereby raising aldehyde
concentrations) and the incidence of aerodigestive tract tumours is
increased. Because alcohol is a solvent, other toxic compounds,
particularly those added to inferior products to enhance palatability,
might also play a part.
The scale of the danger posed by
alcohol is immense. Nearly 2 billion people consume alcoholic beverages
regularly. All families and societies that consume alcohol are affected,
with some populations, such as native Americans, at particularly high
risk of harmful outcomes. Europe is the region of greatest consumption
and has the heaviest burden of alcohol-related cancers. One estimate of
annual consumption in the UK for 2016 was 12 L of pure alcohol for
individuals aged 15 years or older. Populations in eastern Europe drank
even more. Beyond cancer, alcohol has widespread and insidious effects
throughout the body and mind, leading to profound adverse social
consequences. The Global Burden of Disease Study 2016 ranked alcohol as
the seventh leading cause for disability-adjusted life-years (4·2%) and
death (5·2%). In the UK, where classification of alcohol-specific deaths
has been narrowed, there were 7327 registered deaths in 2016, an
age-standardised rate of 11·7 per 100 000.
The ASCO
statement takes the health consequences of alcohol beyond the dawn of
understanding to the full light of day: alcohol is an undeniable menace
to health. Yet it is also culturally bound to the behaviours of almost 2
billion people, for whom, in the coming weeks, large quantities will
feature at Thanksgiving gatherings, seasonal office parties, Christmas
celebrations, and new year festivities. As the Comment in this issue by
Frank Murray about alcohol control in Ireland shows, stricter regulation
of alcohol elicits strong political and commercial opposition. For
those reasons, and because of the influence of alcohol on patients'
wellbeing, moves towards safer drinking need to be led by health
professionals. Routine surveillance, health education, and cancer
prevention provide contexts for doing so within any consultation.
The
challenge of alcohol and cancer will increase. Longer life expectancy
means greater cumulative exposure, and as more populations become
affluent, alcohol consumption grows. Meanwhile, the cost of alcohol in
real terms has decreased, which expands availability. But alcohol is a
modifiable hazard, with a risk that diminishes after stopping. There is
no excuse to ignore regulatory interventions for access, advertisements,
and unit cost that are shown to reduce alcohol consumption. Like
tobacco, the longer the delay in effective control, the more severe
future interventions for alcohol will need to be. It is not unimaginable
that bottles of Château Mouton Rothschild, which once bore the artwork
of Salvador Dali and Pablo Picasso, might one day be required to have
plain packaging and images of oesophageal cancer or a cirrhotic liver.
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