September 30, 2008
Breast Cancer: What Women Need to Know
By Professor Karol Sikora
Can diet and exercise help prevent Britain's most common cancer? And is it really caused by toxins, stress and late childbirth? Professor Karol Sikora debunks the myths - and reports on the latest breakthroughs
Breast cancer is now the most common cancer in the UK. In 2005, more than 45,500 women were diagnosed with the disease, a rate of 125 women per day. It's also on the increase; over the past 10 years, female breast-cancer incidence rates in the UK have risen by 13 per cent. The highest rates are in Northern and Western Europe and North America - the lowest are in North, East and Central African countries, and in Asia.
Historically, the method of battling breast cancer, as with any other cancer, has been to catch it early and treat it thoroughly. But, increasingly, it is becoming possible to predict individual risk of breast cancer and to take preventive action.
A major factor in whether or not you are prone to breast cancer is your genetic background, which is something you have no control over. You are stuck with the stack of genes you've been given. BRCRA1, the gene that indicates that someone is at high risk of breast cancer, is quite easy to identify but it is very rare in someone who doesn't have a strong family history of breast cancer. Unless someone has a strong such history, it's usually not tested for.
It's likely that in the next few years a whole set of other genes will be identified as contributing to cancer risk; in other words, one gene might not do it, but if you express the right combination of genes you might develop the cancer. Identifying if someone is at risk of breast cancer is important, because it means that you can then be tailor-made a lifestyle that is more likely to stop the cancer from developing. For someone who is at very low risk of breast cancer, you might give them a mammogram at 50 and that's it. If, on the other hand, they have an 80 per cent chance, then they might have one every year and also be recommended certain medications plus one or two changes in lifestyle.
We will soon develop better tests than mammography, which is clumsy. It's a very cheap test, but it quite often produces results that indicate abnormalities which then turn out to be nothing. Psychologically, this is very damaging because women then have to be recalled and, naturally, they panic while they're waiting to be called back.
Once you have identified someone with a high risk of cancer, you can begin to develop personalised drugs to prevent it. One of the things about cancer is that it does seem to be a disease of inflammation. So a preventive thing you can do is to take an anti- inflammatory; the most obvious one is a low dose of aspirin, and there is some evidence that that is useful. I, personally, don't recommend taking it, but some do and it's something that is more common in America. There is some evidence of benefit from that and it's linked to the prevention of heart-disease as well. So, at the moment, the most often-used preventive medication for breast cancer is an anti-inflammatory such as Tamoxifen, and we will start to see even more clever drugs than that. They are being developed now and are not yet available; clinical trials take a long time and you can't get any results within, say, a year - you have to wait five or more probably 10 years.
Breast cancer is a disease driven by the hormonal state of women during their lives, so using hormones as a preventive treatment is something that might happen more in future. What's standing in the way of cancer-preventive drugs isn't that people don't want to manufacture them, but a) there's no way of identifying a group of high-risk people except with the BRCRA1 gene in order to test a compound on; and b) there is no short-term biomarker to indicate a drop in something. For example, with cholesterol we give the drugs to reduce cholesterol, so as to reduce the chance of a heart- attack. Within a month of taking a statin, cholesterol falls, and then we know that the patient is less likely to have a heart attack or get heart disease. The problem with breast cancer is that we don't have such a biomarker indicate whether a medicine is working or not.
One of the theories as to why rates of breast cancer have gone up, not just in this country but in other middle-income countries around the world, is that women are having children later in life. There does seem to be something preventive about having a child when you are a teenager rather than later, in your twenties and thirties. But this is only statistics. A lot of statistics that link certain things with breast cancer are just associations, with no real mechanism or explanation behind them - we make up mechanisms to try to explain them.
If a woman breast-feeds her babies, there are protective factors for the mother against breast cancer. As women usually breast-feed between the ages of 20 and 30, it will offer protection for her later in life. Breast-feeding when younger is a preventive measure for the time when the cancer is most likely to develop - between the ages of 50 and 60 - so it seems to protect women against the beginning stage of the disease. If everyone breast-fed their babies, there would be one fewer woman in 20 diagnosed with breast cancer, so about 5 per cent less.
DIET AND EXERCISE
Similarly, there is a link between obesity and breast cancer, so the obvious advice is not to get overweight and to eat healthily - with fruit and vegetables being the main component of a good diet. There's nothing magic about the five portions of fruit and vegetables a day rule, but it is a good indicator of the sort of things you should be eating, which will increase your chances of not getting cancer - not just breast cancer, but a whole series of other cancers.
The media love the concept of cancer-busting foods, but it's broadly a myth. There is nothing especially dynamic about any of them, and eating a wheelbarrow-full of watercress won't stop you from getting cancer. The idea springs from the fact that, while fruit and vegetables all contain antioxidants, which are very good for us, some have more than others.
Per gram, certain foods do have slightly more cancer-preventing features. Tomato-skins have lycopins in them, which may well be associated with cancer prevention. But you shouldn't let that stop you from getting your antioxidants from wherever you like. If you like celery, eat that; if not, eat broccoli or whichever you prefer.
The results of a Europe-wide study, called The European Prospective Investigation into Cancer and Nutrition, will be very instructive about the links between diet and cancer. Europe is a natural laboratory, with a wide range of different diets to study. Half a million samples and histories were taken, from the high-fat diets of Norway to the high olive-oil and fish diets of southern Italy. The results should allow some hypotheses to be drawn up as to the effect of diet on various forms of cancer. The tricky thing will be identifying what exactly about the diet is preventive - it may be a combination of things.
The effect of external toxins on the development of cancer is often overstated. A few years ago, deodorants were cited as a possible cause of cancer, but there's really no evidence. It's as tricky as proving a link between mobile phones and brain tumours. For example, how do you quantify deodorant use? If you sat down with a group of women who have breast cancer, and then another group of the same age who haven't, and then try to separate out the use of deodorants, it becomes very complicated.
People in the complementary sector get very excited about pesticides and other modern farming practices being linked to cancer, and about the fact that farm animals are often injected with steroids. But the evidence is pretty weak that this has any significant effect. There is some evidence, but it is below the 5 per cent mark - in fact, probably far below that.
The link between alcohol and breast cancer is tenuous, but it is there. Alcohol changes a hormonal mechanism, but the extent of this has not yet been worked out. It somehow affects a woman's hormonal balance, so although the possible development of breast cancer is unlikely to be due to the consumption of alcohol itself, it does indirectly act as a link.
People have looked into the possible connection between stress and breast cancer, and it is an interesting possible link. There is some evidence, although it is not very strong, that the spread of the disease is affected by stress. Very stressful episodes in life might be the loss of a child through bereavement, the loss of a parent, or the loss of a partner. Divorce and moving house are other very stressful events.
The difficulty in all the studies is that the diagnosis of stress often comes after the cancer has developed. People think that they have been under a lot of stress for the past year or so; then they are diagnosed with cancer and they attribute it to the stress. But the cancer cells probably first developed many years before the disease was diagnosed. You would have to look at stressful events several years previously, and the link is not always easy to find.
We don't know if complementary or relaxation therapies have much of a preventive effect. The work simply hasn't been done on this. One theory is that complementary therapies often involve some sort of relaxation - even things such as acupuncture involve relaxation. That can reduce stress levels and have an effect on your hormones in a positive way.
It's not that complementary therapies don't have a role; it's just that it's too complicated to work out what exactly this role is. One obstacle to research is that the kind of people who are interested in complementary therapies are the kind who are also likely to take better care of themselves, especially on diet, which would affect the definitiveness of the results.
Karol Sikora, Professor of Cancer Medicine and honorary consultant oncologist at Imperial College School of Medicine, London, was interviewed by Esther Walker
(c) 2008 Independent, The; London (UK). Provided by ProQuest LLC. All rights Reserved.