Does drinking alcohol mean you have more chance of dying from breast cancer?

Surprisingly no.

(a shorter version of this article is available here)

Women who drink alcohol have no more chance of dying from breast cancer going fo.

There is slightly more chance that your inevitable death will be from breast cancer, but (and it’s a big but) only because drinkers are much less likely to die from heart disease, and you have to die from something, eventually.

That’s what the scientific evidence says. Which is fantastic news for women.

Yes, it surprised me. I was used to reading Public Health advertising saying how drinking a single glass of wine a day increases risk. I’m sure women have noticed many more of these announcements than I have. But, rather shamefully, these messages are causing unnecessary worry and guilt.

An analysis of various causes of death of middle aged and elderly Americans (Thun et al 1997) found that of the 230,552 women in the study, 0.3% of the zero and super-light drinkers contracted and died from breast cancer as the cause, over the 10 years of study observation. They were no more or less likely to die from breast cancer than the moderate and heavy drinkers (1 to 4+ drinks per day), 0.3% of whom died due to breast cancer. So drinkers had no more chance overall of dying from breast cancer (even though the drinkers cohort were more likely to smoke than non-drinkers).

There were 13,669 deaths among the 251,420 women in the study. Of these deaths 4.6% were due to breast cancer among non and super light drinkers (zero to less than 5 grams of alcohol per day) , while 6.2% of the deaths were due to breast cancer among those who drank 5 to 30+ grams per day. This looks like a higher rate amongst drinkers, but it’s an illusion, the difference is being due to fewer of the drinker’s deaths being from heart and cardiovascular disease (33% c.f. 43% for none/light drinkers) so, mathematically, a greater percent of their deaths simply had to be from other causes.

In another mortality study (35,000 women 34–59 years old, Fuchs et al 1995) the chance of death from breast cancer during the 12 year follow-up period was 0.4%, and again this chance was identical for zero-to-super-light drinkers as with moderate-to-heavy drinkers. And again there was much higher chance of death from cardiovascular disease among the non/light drinkers.

Meta-analysis of the epidemiological studies looking at drinking and breast cancer mortality/survival after diagnosis shows no association between levels of drinking (before or after diagnosis) and risk of breast cancer death, nor reoccurrence of the cancer (Gou et al 2013). A new study from the Women’s Health Initiative (Lowry 2016) looking at patients already diagnosed with breast cancer found no link between mortality and drinking, before or after breast cancer diagnosis. A smaller study of drinking after breast cancer diagnosis, published the same year, shows the same thing: women who drank (at all levels from 1–36 standard drinks per week) before their breast cancer diagnosis had no higher risk of dying from the cancer than the non-drinkers (Din et al 2016). Similarly a large study with long follow-up of women with breast cancer (Newcomb et al 2013) showed breast cancer patients had better chances of survival if they were regular drinkers before diagnosis. If they altered their drinking after diagnosis this did not alter their chance of dying from breast cancer. But an increase in drinking was associated with an overall improvement in life expectancy (largely due to substantially fewer heart disease deaths among those who increased their alcohol consumption). This is good causal evidence that alcohol prevents heart disease, and it conflicts with the idea that alcohol causes breast cancer.

Reading all this made me confused, I was sure that there were quite a few population studies that showed that drinkers had a (slightly) higher chance of getting breast cancer. So I went back and checked, and yes there are, but… these are studies of “incidence” (how many women are diagnosed with breast cancer) not studies of mortality (how many women die from breast cancer).

So women who drink alcohol have slightly higher chance of being diagnosed with breast cancer, but if they are they have slightly less chance of dying from it. That doesn’t seem to make sense. So I read a bit more. It turns out that most women (90%) who are diagnosed with breast cancer don’t die from it, partly because medical science cures many of them, but also because many of the diagnoses are incorrect (or at least were for non-life threatening breast cancer). Screening programs for breast cancer are quite controversial, because they have done little or nothing to reduce breast cancer deaths, while they do increase the number of women diagnosed with cancer. This is what makes them controversial, they not only cost governments money (that could be spent on other health initiatives) they cause some unnecessary treatments and much unnecessary anguish and stress. Being diagnosed with breast cancer doesn’t mean you actually have cancer, or at least not cancer that you should worry about.

I recall my grandmother, who used to work for the Cancer Society, saying that Japan had low rates of breast cancer. She was right, yet Japan has a very similar rate of breast cancer mortality as the USA. Which seems very odd, until you realise that in Japan they screen far less. So fewer women are diagnosed (lower incidence).

So this is why the studies seem to conflict. It’s just like the difference between Japan and the USA. Women who drink alcohol tend to screen more for breast cancer (shown in the USA in Mu and Mukamal 2016). Probably because they are wealthier, more urban, more health conscious, or simply live closer to screening clinics.

So the link between drinking and breast cancer incidence is spurious, not causal, or at least far less than we thought. None of the studies that reported such a link between drinking and diagnosis of cancer controlled for screening incidence, clearly they really should have.

Land et al 2014, perfectly controlled for screening by actually screening all their subjects. The results showed no link between drinking and breast cancer — indeed drinking was associated with slightly less risk of cancer (of both breast and colon cancer).

Interestingly the weak correlations seen in population studies have long been questioned by at least some scientists. Back in 2003 Science published a special news report on the limits of epidemiology (Taubes 2003):

“I’d bet right now there isn’t a concensus. I do know just from talking to people that some hold it’s a risk factor and others deny it.” Another Boston based epidemiologist, who prefers to remain anonymous, says nobody is convinced of the breast cancer — alcohol connection.

Since then a concensus emerged, but the wrong one.

It’s now time for us to tell women the good news.

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References

Din N; Allen IE; Satariano WA; Demb J; Braithwaite D. (2016) “Alcohol consumption and mortality after breast cancer diagnosis: the Health and Functioning in Women study”, Breast Disease Vol 36, No 2–3, 2016, pp77–89.

Fuchs, Charles S. , Meir J. Stampfer,, Graham A. Colditz, , Edward L. Giovannucci, JoAnn E. Manson, Ichiro Kawachi, David J. Hunter, Susan E. Hankinson, Charles H. Hennekens, Bernard Rosner, Frank E. Speizer, and Walter C. Willett (1995) “Alcohol Consumption and Mortality among Women”, N Engl J Med; 332:1245–1250 May 11, 1995 DOI: 10.1056/NEJM199505113321901

Gou, Xie, Yang, Liu, Zhang, Li, and He (2013) “Alcohol Consumption and Breast Cancer Survival: A Meta- analysis of Cohort Studies”, in Asian Pacific Journal of Cancer Prevention, Vol 14, No 8, pages 4785–4790. DOI:http://dx.doi.org/10.7314/APJCP.2013.14.8.4785

Land, Liu, Wickerham, Constantino, and Ganz (2014) “Cigarette smoking, physical activity, and alcohol consumption as predictors of cancer incidence among women at high risk of breast cancer in the NSABP P-1 Trial”, in Cancer Epidemiology Biomarkers and Prevention, 23(5): 823–832. doi:10.1158/1055–9965.EPI-13–1105-T

Lowry, Sarah J. and Kris Kapphahn, Rowan Chlebowski, and Christopher I. Li (2016) “Alcohol Use and Breast Cancer Survival among Participants in the Women’s Health Initiative”, in Cancer Epidemiology, Biomarkers and Prevention, 25(8); 1268–73. doi: 10.1158/1055–9965.EPI-16–0151

Mu L, and KJ Mukamal (2016) “Alcohol consumption and rates of cancer screening: Is cancer risk overestimated?”, in Cancer Causes Control, Feb, 27(2):281–9. doi: 0.1007/s10552–015–0692–3.

Newcomb Polly A. and Ellen Kampman, Amy Trentham-Dietz, Kathleen M. Egan, Linda J. Titus, John A. Baron, John M. Hampton, Michael N. Passarelli, and Walter C. Willett (2013) “Alcohol Consumption Before and After Breast Cancer Diagnosis: Associations With Survival From Breast Cancer, Cardiovascular Disease, and Other Causes” in Journal of Clinical Oncology, DOI: 10.1200/JCO.2012.46.5765

Taubes, Gary (1995) “Epidemiology faces its limits”, in Science, 269:5221, 164–69.

Thun, Petro, Lopez, Monaco, Henley, Heath and Doll (1997) “ALCOHOL CONSUMPTION AND MORTALITY AMONG MIDDLE-AGED AND ELDERLY U.S. ADULTS”, in The New England Journal of Medicine, Vol.337, №27.