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New drug can reduce breast cancer recurring by more than one third -

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ELEANOR HALL: A global study into breast cancer has found that a new treatment can reduce the risk of recurrent cancer in young women by more than a third.

The researchers studied 5,000 women across 27 countries and released their results at an international conference in Chicago.

One of the lead authors of the study is Associate Professor Prue Francis from Melbourne's Peter MacCallum Cancer Centre.

She spoke to Alison Caldwell.

PRUE FRANCIS: So basically Exemestane is an aromatase inhibitor. And aromatase inhibitors in the last 10 years have really become a standard of care for women, post-menopausal women, with hormone-sensitive breast cancer.

But we weren't able to use aromatase inhibitors for pre-menopausal women because they only work if women have a low estrogen level as in post-menopausal women.

ALISON CALDWELL: What does aromatase mean?

PRUE FRANCIS: An aromatase inhibitor means that it blocks the production of estrogen in post-menopausal women.

ALISON CALDWELL: And it's the estrogen that feeds cancer cells, isn't it?

PRUE FRANCIS: That's right. So women with hormone-sensitive breast cancer, the estrogen can potentially stimulate the growth of cancer cells in those women. So an aromatase inhibitor blocks in older women the production of estrogen and therefore potentially removes something that might stimulate cancer cells.

ALISON CALDWELL: In the trials that you did, how is Exemestane shown to be more effective for these younger women than Tamoxifen?

PRUE FRANCIS: What we did in the younger women is that all the younger women we suppressed the function of their ovaries for five years to try to simulate the estrogen levels that we see in older, post-menopausal women. And then half of the women were allocated to receive Tamoxifen and half to the aromatase inhibitor Exemestane.

And what we found was that the women that were allocated to the Exemestane with the suppression of the ovarian function were less likely to have further recurrence or problems with their breast cancer over the next five years than the women that received the Tamoxifen with the suppression of ovarian function.

ALISON CALDWELL: And it was something like it reduced the risk of further breast cancer after surgery in young women by 34 per cent or a third?

PRUE FRANCIS: Yes. So that's a relative risk reduction of about 34 per cent. And what that translated to in absolute numbers, if you look at it, we had about 88.8 per cent of the women who got Tamoxifen with suppression of ovarian function remained free from cancer over the next five years.

And for the women that got the newer treatment with the Exemestane aromatase inhibitor with the suppression of ovarian function, there were 92.8 per cent. So it was an extra four women out of 100 in these younger women who remained free from breast cancer over a five-year period.

Now, obviously suppressing the ovarian function of young women comes potentially with some side effects, but, you know, it will change treatment. In some countries it's fairly common to suppress ovarian function in women who are pre-menopausal and have hormone-sensitive breast cancer. It's a common treatment anyway. And in those countries this will really become a standard of care.

ALISON CALDWELL: Is Australia one of those countries?

PRUE FRANCIS: Australia is probably not one of the countries where it's routine. Australia probably does suppress ovarian function in a sub-population of women but it's probably not in all women who are pre-menopausal and have hormone-sensitive breast cancer.

But I think that, you know, there will be oncologists and women who will look at these data and they will start to think about whether this would be an appropriate treatment for that particular woman. And I guess the women who probably are at highest risk of having their cancer returning, this for them might be a treatment that they would certainly want to consider.

ALISON CALDWELL: How common is hormone-responsive breast cancer?

PRUE FRANCIS: So, if you look at all pre-menopausal women who get breast cancer, it's really about 80 per cent of them. So about, you know, four out of five pre-menopausal women will have hormone-sensitive breast cancer. So it's the majority of young women could potentially be in this category.

ELEANOR HALL: That's medical oncologist Associate Professor Prue Francis, speaking to Alison Caldwell.