In keeping with the international trend, we have just had breast cancer awareness week in the UK. Women were told to have mammograms, to take exercise, to avoid hormone replacement therapy, to breastfeed. All good. But, as usual, certain other things we should do or avoid were not mentioned.
A woman would never guess, for example, that the choices she makes about pregnancy and childbirth can raise or lower her risk of breast cancer. Taking the contraceptive pill, delaying her first child, aborting a pregnancy - these things are among the factors driving the "epidemic" of breast cancer among younger women. Doesn't she have a right to be told?
It has long been known that having children tends to protect women against breast cancer. Even in medieval times it was noted that nuns were more prone to this disease. We can now quantify this and say that women who have children reduce their risk of breast cancer by as much as 90 percent compared with women who remain childless. Each full-term child lowers its mother's risk by 10 percent.
On the other hand, a woman's risk of developing cancer before menopause is raised by 5 percent for each year after the age of 20 that she delays childbearing. Thus, women who delay full-term pregnancy to age 30 have a 50 percent higher risk than those who carry a pregnancy to term by age 20.
We are talking statistics and averages here, and focusing on one kind of cause, but the figures are significant, and reproductive history is much more important than is often acknowledged.
I learnt my science from the respected American breast surgeon Dr Angela Lanfranchi , co-founder of the Breast Cancer Prevention Institute . She and I were in Australia for a speaking tour a couple of months ago, and over the days I was with her I discovered fascinating facts which every woman should know.
Dr Lanfranchi's topic for her Australian presentations was the link between abortion and breast cancer (the ABC link) which is what I want to focus on here, since abortion is, along with hormonal contraception, one of the risk factors that women have most control over.
The New Jersey surgeon and professor explains this by describing the physiology of the breast in layman's terms. Apparently breast tissue contains four types of lobule:
Before a full-term pregnancy, the breast is composed of 75 percent Type 1 and 25 percent Type 2 lobules. It is in these two types of lobule that cancer can form. If a woman never has a pregnancy, she retains these lobules in their premature state.
Types 3 and 4 by contrast resist cancer.
As soon as conception occurs, the embryo secretes the hormone hCG (Human chorionic gonadotropin) which causes the mother's ovaries to produce more oestrogen and progesterone which in turn cause the breasts to grow. So fast do they grow that they actually double in volume in 20 weeks. Obviously what grows are the Type 1 and 2 lobules, which are prone to cancer.
After 32 weeks, Types 1 and 2 mature into Type 3 and 4 lobules, in preparation for breastfeeding.
If pregnancy ends by elective abortion before 32 weeks, the increase in numbers of Type 1 and 2 lobules provide more places for cancers to start. If you add to this the risk that is already associated with delaying childbearing, you can see the ABC link strengthening.
Women who have abortions often compound their risks by using hormonal contraceptives. Abortion also increases the risk of future pre-term births and therefore of cancer, since delivering before 32 weeks doubles breast cancer risk.
However, miscarriage during the first trimester does not normally have this effect. Female hormone levels tend to be much lower in women who miscarry, and without raised oestrogen the woman's breasts remain unchanged. Miscarriage during the second trimester does raise the risk, for the same reasons as induced abortion does, as these miscarriages usually occur in hormonally normal pregnancies.
It is no secret that the ABC link is controversial. Indeed, most scientists in the field deny it, arguing that if induced abortion increases the risk of breast cancer spontaneous abortion, or miscarriages, would do so too. They point to studies that include both types of abortion and seem to show no significant effect on cancer risk.
But Dr Lanfranchi says that, between 1957 and 2013, there have been 72 studies done on breast cancer risk which differentiate between spontaneous and induced abortion. Of these, 56 showed a positive ABC link and in 33 the effect was statistically significant. She explained some of these studies to us, and even as a layman I found them convincing.
A most interesting case is that of Romania. Between 1957 and 1966, abortion was legal there on demand and was commonplace; in fact, 80 percent of pregnancies ended in abortion. However, Ceausescu's government, wishing to raise the country's birth rate, outlawed most abortion in 1966, so the rate fell drastically. In 1989, after the Romanian Revolution, abortion was again legalised and surged. You can see correlating figures for breast cancer rising and falling among Romanian women.
We all know that breast cancer has become a major scourge in society. It is causing special concern in China and East Asia -- Dr Lanfranchi was invited to Shanghai to advise their health care authorities.
However, what drives her to campaign for better awareness is her own experience as a breast surgeon. Over the last twenty years, she has seen 20,000 patients in her New Jersey surgery, and she says she cannot keep quiet about what she is seeing. "These are not statistics. These are women, often young, sometimes with small children. If you could see these lovely young people on my operating table you would know why I have to expose this tragedy."
Her point is not that anybody should tell others how they should run their lives. "What is wrong is that nobody is telling them what they risk so that they can make good choices." She adds, "Why are we not offering earlier scans to those most at most risk? If you wait till they're 50, it's too late for many. Women who have had an abortion should be scanned 8-10 years after the event."
Dr Lanfranchi was quick to reassure us that, even with all this data, the risk is small. By meta-analyses, there is only a 30 percent increased risk of breast cancer, considered low by epidemiologic standards. For example, cigarettes, which increase the risk of lung cancer over 1000% , is considered a large risk. Unfortunately, in some circumstances, induced abortion can increase risk over several hundred percent, for example teenagers getting abortions in the second trimester.
"I'm not saying that every woman who has an abortion is going to get breast cancer, and I am certainly not saying that every woman who has breast cancer has had an abortion or used hormonal contraceptives. But what I am saying is that when there is a worrying surge in breast cancer worldwide, you cannot ignore the connection with delaying pregnancy or cutting it short. Individual risk may be small, but a small risk often repeated begins to take a measurable toll on society."
Around 50,000 women are diagnosed with breast cancer each year in the UK and 1 in 8 women will receive such a diagnosis in their lifetime. Early detection through a national screening programme and treatment ensures that most survive, but around 32 women a day die from the disease. This loss of life, and the cost of the disease to society, should mean that health officials and experts are open to any evidence that would help prevent it. Instead, we have the studious silence about abortion seen during last week's campaign.
In Australia, it was worse. Dr Lanfranchi's presence caused a cacophony of protest in the media, which led to us being dropped from being guests of honour at a distinguished lunch, and to the owners of our conference venue in Melbourne being threatened with vandalism to their property. The conference had to move venue four times. So much for freedom of speech. So much for those high profile groups who could so easily help to reduce the world's breast cancer.