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Large Victorian study confirms abortion is not a breast cancer risk factor

Monday 29 September, 2014

A collaborative research team from Cancer Council Victoria, the Peter MacCallum Cancer Centre and The University of Melbourne has confirmed that abortion does not increase the risk of developing breast cancer, after analysing prospective data gathered from more than 24,000 Victorian women over 18 years.

Lead author and Cancer Council Victoria epidemiologist Dr Roger Milne says the findings, published in the Medical Journal of Australia today, are robust because they are based on a large prospective cohort study. Women were recruited to the Melbourne Collaborative Cohort Study between 1990 and 1994, when aged between 40-69, asked about all their pregnancies and other potential risk factors, and then followed until 2012 to determine who developed breast cancer.

"Retrospective case-control studies tend to give biased results, most likely because women with breast cancer are more likely to report previous abortions than women who don't have cancer.

"Our prospective study avoided this bias because the information on abortion was collected before any of the women developed cancer."

Medical Oncologist at Peter Mac, Professor Kelly-Anne Phillips, says the results of the large study replicate several international findings by confirming the risk of breast cancer does not increase after an abortion.

"The findings were consistent after taking into consideration age at first menstruation, use of oral contraception, number of full-term pregnancies, age at first birth and lifetime breastfeeding.

"The result was also similar for abortion before first full-term pregnancy and in the first two trimesters."