IARC 50th Anniversary Conference

Breast and cervical cancer rates influenced by HRT, not contraceptive pill

Prof Valerie Beral - University of Oxford, Oxford, UK

The thing about women’s cancer is that 40% of all cancers that occur in women are cancers of reproductive organs, female specific cancers of the breast, ovary or uterus whereas in men, for example, it’s only about 15% are cancers of the prostate or testes. So a very large proportion of cancers in women are female specific cancers.

How are you tackling prevention?

It varies for every cancer and I’ll just talk briefly about each cancer. For cancer of the cervix we’ve known for a long time it’s sexually transmitted, that screening by Pap smear works very well and now we’ve got a vaccine against papilloma virus. So we know, really, what to do about preventing cervical cancer. It’s very hard to implement but we’ve really got the clues to the big picture; we know the big picture, we know the big solutions but implementing them is very hard.

For cancer of the womb, that’s endometrial cancer, and for cancer of the ovary, both of which, cancer of the womb is a bit more common than cancer of the ovary but not much. The main thing we know which curiously is not said as often as it should be and it’s been known for decades is that the pill has a long-lasting strong protective effect. People who have taken the pill when they were in their teens, twenties or thirties, for ten years have a halving of the risk of endometrial and ovarian cancer which is very profound. We estimated, based on the worldwide evidence, that so far about 400,000 endometrial cancers have been prevented by the pill and 300,000 ovarian cancers. It’s a very easy thing and we know that there are no long-term adverse effects of the pill so I think that there should be a lot more said about young women should be encouraged to take the pill.

What issues are there regarding breast cancer?

Breast cancer is more common than the other three put together and it’s particularly common in the West. We actually know, and I wasn’t the only one to have said so far at this meeting, when you go through all the evidence that we’ve got about breast cancer we actually understand most of why breast cancer is common in the West and most of it is because of childbearing patterns. If women in the West had as many children as, say, in low income countries and breastfed them for as long, had six or seven children, breastfed each for two years you would more than halve breast cancer rates. Then there are other things that add a bit like people who are overweight, people who drink alcohol and use hormone therapies, there are other things but they are not the big story. The big story is childbearing patterns. The sad thing about that, and I will say that that’s because a lot of my work has been looking at hormones and breast cancer, the pill and hormone replacement therapy, and when I started in research people used to say the reason breast cancer is common in the West is because of the childbearing differences, having children, but the effects of children is mediated by oestrogens and progesterones. So if that was true the pill should have protected against breast cancer and it doesn’t which means that we don’t know how to prevent breast cancer.

Can you discuss the fear surrounding the pill and HRT?

They should be afraid of HRT, HRT, particularly the combined oestrogen plus progesterone, really has a very bad effect on breast cancer. There is a big risk. But the sad thing, the pill actually slightly increases breast cancer risk while it’s being taken but it goes away, it’s not a persistent factor. It’s quite different to the effects of the pill on endometrial and ovarian cancer where it’s strongly protective.

What are the key messages in regard to prevention?

The overwhelming evidence at the moment is that the pill, on balance, everything put together, women who have taken the pill for a long time are less likely to get cancer in total than women who haven’t and it’s largely because of this long-term protection against ovarian and endometrial cancer. Sadly the pill does not reduce the risk of breast cancer, if anything it slightly increases the risk in the short term. But that’s not a very big effect. So the pill in the long term, and women who have taken it are better off in terms of cancer. There’s no reason, in my mind, why they shouldn’t be told that more clearly and that really taking the pill for a long time is a good thing.

In relation, is there a message on tobacco, alcohol and diet?

Diet has no role in these cancers, just as a summary and I think that’s generally agreed. Diet doesn’t and effectively tobacco doesn’t have much effect either. It’s neither diet or tobacco. Alcohol does, alcohol does increase breast cancer risk and that’s quite important, particularly people are drinking more than they used to, but tobacco doesn’t have much of a role.

What are your recommendations to women?

Screening works for breast cancer, screening works for cervix cancer so go for screening. For cervix cancer young people should be vaccinated. In general taking the pill for prolonged periods is good for cancer in the long term; there’s a very small increase in breast cancer risk in the short term but that goes away, but there’s profound and long-term lifelong protection against cancer of the ovary and endometrium. That is good. Hormone replacement therapy, particularly combined, it really does have a substantial increase in breast cancer risk.