Study: IVF + Cancer Risk

Women who undergo test-tube fertilization programmes are no more likely to develop breast or ovarian cancer than other women, an Australian research group said on Friday after a 20-year study.

The study focused on 29,700 Australian women who used the test-tube method, known as in-vitro fertilization (IVF), in clinics between 1978 and 1993-- making it the largest research programme of its type in the world.

"We have specifically addressed the issue of whether IVF patients are having more cancers than other women in the general population and we can say they are not," epidemiologist Alison Venn, from Melbourne's LaTrobe University, told Reuters.

IVF treatment involves removing eggs from a woman and sperm from a man then fertilizing them in a lab dish instead of naturally within the body. There has been unease over whether hormones given to women during IVF treatment could increase the risks of breast and ovarian cancer.

The study, published on Friday in Britain's Lancet medical journal, followed the women from between one and 22 years, with the majority assessed for five to 10 years.

Of the 29,700 women, researchers had predicted, on the basis of normal population rates, 155 breast cancers, and found 143 cases. They predicted and found 13 cases of ovarian cancer.

But Venn said the study revealed an increased risk in very small sub-groups of women. Those with unexplained infertility had higher-than-expected rates of ovarian and uterine cancer.

She said the risk groups involved very small numbers and that further studies would be done.

Venn said the study showed that more women than expected were diagnosed with breast cancer in the first year after treatment with fertility drugs -- with nine predicted and 17 detected.

But she said the finding could be due to increased medical supervision for those women at that time, reflecting earlier detection rather than more cases.

Venn said there could also be a biological explanation, that hormonal changes as a result of pregnancy or fertility treatment could affect the growth of existing tumours, but she said they could not be held responsible for causing the cancers.

"You can't cause breast cancer that quickly," she said.

Venn said the research team wanted to continue its study of the women as they grew older, and to look more deeply into the reasons for increased rates in certain sub-groups.

"But in terms of the very large numbers of women who have been in IVF programmes in Australia, the findings are really largely reassuring, and I think that is important in itself."