Two important studies late in 2002 highlighted the increased risk
to women of developing breast cancer at even moderate levels of
alcohol consumption. Previous research has suggested that postmenopausal
women who either drink alcohol or use hormone replacement therapy
(HRT) have a higher than average risk of breast cancer, and the
studies suggest that the combination of both could up the risk
more than either alone.
There are approximately 600,000 new cases of breast cancer each
year world-wide. Breast cancer is the most common cancer among
women in the United States accounting for a quarter of all female
cancers and is second only to lung cancer as a cause of cancer-related
deaths.Cancer Research UK estimates that alcohol accounts for
around 4% of breast cancers in the developed world and that one
in eight women will develop breast cancer during her lifetime.
Over the past 10 years, the incidence of breast cancer has remained
unchanged, although mortality rates have steadily decreased, due
to earlier detection and more effective therapy.
Risk factors include age (the risk for developing breast cancer
by age 40 is 0.5%, compared with 10% by age 80), as well as lifetime
exposure to unopposed oestrogen (early menarche, late menopause,
late first pregnancy or prolonged use of oestrogen-based oral
contraceptives). Women with certain benign proliferate lesions
of the breast, as well as those with a premalignant condition
called carcinoma in situ, are also at increased risk for developing invasive breast cancer,
and individuals who have already sustained one breast cancer are
at increased risk for a second primary tumour.
Germline mutations in the breast cancer genes BRCA1 and BRCA2, present in about 0.1% of the general population, are associated
with a high lifetime risk for developing breast cancer at an early
age, as is a family history of breast and/or ovarian cancer. Hormonal
risk factors are likely to modulate genetic predisposition to
breast cancer, although the magnitude of this effect is unknown
and inherited mutations are believed to account for approximately
5% of breast cancer cases. Environmental factors, including diet,
alcohol intake and obesity, have been suspected but not consistently
linked to increased breast cancer risk. However, according to
a recent meta-analsis on the effects of alcohol and smoking on
breast cancer risk published in the British Journal of Cancer,
a womans risk of breast cancer increases by 6% for each alcoholic
Researchers combined results from more than 50 studies and included
data on around 150,000 women from around the globe. Over 23,000
of these women did not drink and looking at this group separately
the researchers could see no significant difference between rates
of breast cancer in smokers and non-smokers.
Sir Richard Doll, a co-author of the study, says: "For the first
time we have undertaken a study large enough and detailed enough
to look at the separate effects of tobacco and alcohol reliably.
When we did this we found that drinking, but not smoking, increases
the risk of breast cancer." Co-author Professor Valerie Beral,
of Cancer Research UKs Cancer Epidemiology Unit at the Radcliffe
Infirmary in Oxford, says: "This research tells us there is a
definite link between alcohol and breast cancer and the evidence
suggests that the more a woman drinks the greater her risk".
The average alcohol intake for UK women has increased from about
7 grams to 8 grams per day in the last decade, but among women
aged between 16 and 24, the proportion drinking more than three
drinks per day has doubled from nine per cent to 18 per cent.
Dr Gillian Reeves, a co-author, commented "The balance between
the harmful effects of alcohol on breast cancer and its beneficial
effects on heart disease depend on a womans age. Before about
60, breast cancer is a more important cause of death than heart
disease. After the age of 65 or so, when the risk of heart disease
becomes much greater than the risk of breast cancer, the benefits
of moderate drinking are more apparent." Sir Paul Nurse, Cancer
Research UKs Chief Executive, says: "Large studies of this kind
are very important for dissecting the complex causes of cancer.
This research doesnt alter our advice on smoking because we already
know that its dangerous but it does reinforce our advice that
excessive drinking can also be hazardous."
The second study by Dr. Wendy Y. Chen of Brigham and Womens Hospital
and the Dana-Farber Cancer Institute in Boston, Massachusetts
was published in the Annals of Internal Medicine.
Based on results from a group of more than 44,000 women, the investigators
discovered that women who either drank at least 1-1/2 alcoholic
drinks each day or took HRT for at least 5 years appeared to have
a 30% increased risk in breast cancer, relative to their teetotaller
counterparts who opted out of HRT. The study found that women
who drank an average of less than one drink each day showed no
increased risk of breast cancer. Chen and her colleagues base
their findings on a group of 44,187 postmenopausal women who were
followed for 14 years. A total of 1,722 women developed breast
cancer. Chen explained that the current study did not investigate
how alcohol consumption or HRT could influence the risk of breast
cancer, but said that previous research has suggested that both
can up the risk by increasing levels of oestrogen in the body.
Chen emphasized that the current findings do not suggest that
women need to abandon alcohol all together. "I think it means
you should limit it to less than a glass and a half per day,"
The results are put in perspective by the editorial accompanying
Sir Richard Dolls study; I. dos Santos Silva entitled Alcohol,
tobacco and breast cancer: should alcohol be condemned and tobacco
acquitted? (Br J Cancer 2002;87:) .Dr. Silva concludes: "Alcohol
intake . . . is likely to account, at present, for a small proportion
of breast cancer cases in developed countires, but for women who
drink moderately, its lifetime cardioprotecdtive effects probably
outweigh its health hazards." In his editorial, he also points
out that moderate drinkers live longer than non-drinkers.