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Miscarriage does not increase women’s breast cancer risk

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by Cancer Research UK | News

12 February 2002

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Having a miscarriage does not increase a woman’s risk of breast cancer at any age, according to one of the largest ever studies on the link between reproductive factors and the disease, published in the British Journal of Cancer today.

But the research, which involved nearly 100,000 French women, confirms what scientists had suspected – that women who have children late or start their periods early are at increased risk.

Cancer Research UK reveals the findings at a special press briefing this morning to relaunch the British Journal of Cancer, which it owns. The journal will now be published by Nature Publishing Group – the world leaders in scientific publication – helping it to expand its global readership and to further its reputation for high class science.

In the new study, researchers tracked women over a ten-year period, sending them detailed questionnaires and recording both reproductive factors and whether or not they developed breast cancer. Premenopausal and postmenopausal women were studied separately, in order to find out whether reproductive factors affected the two groups differently.

Of the 91,000 women in the study, 1,718 were diagnosed with breast cancer over the time period. Previous research on miscarriage had produced conflicting results, with some smaller studies suggesting that it might increase the risk of the disease and a recent paper also linking abortion with increased risk. But the new, large-scale research found no evidence that women with a history of miscarriage were at higher risk of breast cancer in either the premenopausal or postmenopausal group.

Study author Dr Francoise Clavel-Chapelon comments: “In the past, the fear of breast cancer has added to the anxiety already felt by women who have miscarried. I’m very glad to be able to allay those fears.”

Dr Clavel-Chapelon and her colleagues made a number of other interesting findings. Women who had their first child relatively late did seem at increased risk of the disease, with the increase appearing to be greatest in the premenopausal group.

Compared with those who gave birth before the age of 22, women who had their first child in their thirties were 63 per cent more likely to develop breast cancer before the menopause and 35 per cent more likely to get the disease afterwards.

One of the study’s most intriguing findings was that the later a girl started her periods, the lower her chance of developing breast cancer later in life. A woman whose periods had started at the age of 15 was at only two thirds the risk of premenopausal breast cancer of someone whose periods had started at 11, with a decrease of 7 per cent for each year that periods were delayed.

Dr Clavel-Chapelon adds: “Our study has provided all sorts of information about the influence of reproductive and hormonal factors on the development of breast cancer. This information will help us to understand the mechanisms by which breast cancer develops. It’s especially interesting that the influences on a woman’s risk of breast cancer can be so different before and after she reaches the menopause.”

Prof Gordon McVie, Joint Director General of Cancer Research UK, says: “The link between reproductive factors, fluctuation in hormones and women’s breast cancer risk is extremely complex, and previous small-scale studies have often produced confusing and conflicting results.

“Only by looking at very large numbers of women, as this study has, can we start to build up a picture of how and why breast cancer develops.”

Prof Robin Weiss of University College London, Editor of the British Journal of Cancer, says: “Dr Clavel-Chapelon’s work is an important contribution to our understanding of the factors that affect the risk of breast cancer. It’s typical of the kind of interesting and clinically relevant work which the British Journal of Cancer attracts. With the support of Nature Publishing Group and owners Cancer Research UK, we are taking the British Journal of Cancer forward as one of the leading international journals on the progress in understanding, treating and preventing cancer.”

Sue Deeley, Associate Director, Nature Publishing Group (NPG), says: “NPG is delighted to be publishing the British Journal of Cancer in partnership with Cancer Research UK. NPG will apply the skills and resources that make it one of the world’s leading publishers to increase the journal’s worldwide profile.

“The papers published in the British Journal of Cancer will achieve high visibility among both clinicians and researchers globally.”