Side effects predict succes of breast cancer treatment

Hot flushes, night sweats and painful joints can be a blessing in disguise for breast cancer patients - according to a new report published online in the Lancet Oncology.

Cancer Research UK scientists have found that women who take tamoxifen or anastrozole and suffer these side effects are 10 per cent less likely to have a recurrence of breast cancer than women who do not develop these symptoms.

Professor Jack Cuzick, Cancer Research UK epidemiologist and lead author of the study, said: "Our study found that hot flushes, night sweats and painful joints could be used to predict how effective a breast cancer patient's hormonal treatment will be.

"Women who reported any of these symptoms within three months of starting treatment with tamoxifen or anastrozole were less likely to have a recurrence of breast cancer, compared to women who did not experience them."

"The treatment is designed to starve potential cancers of oestrogen and these symptoms mean that there are lower levels of oestrogen in the body. But it is too early to say whether having these symptoms is essential for the treatment to be effective. At the moment all we can say is that the symptoms indicate the likely success of the treatment."

The study is based on data gathered during the ATAC trial*. The researchers found no difference in the chance of cancer recurring among women who reported these symptoms before treatment began.

More than 9,000 women took part in the trial and more than half of them reported at least one of these side effects.

Dr Lesley Walker Cancer Research UK's director of cancer information, said: "The study shows that early side effects from breast cancer drugs could indicate how likely it is that a woman's cancer will return. This could help doctors to better target future treatment for individuals.

"We need more research into the genetics behind individual patient responses to cancer treatment."

* ATAC (Arimidex, Tamoxifen, Alone or in Combination) was a large phase 3 clinical trial published in December 2004, comparing anastrozole (Arimidex) with tamoxifen for post menopausal women who had early stage breast cancer. The results were similar regardless of whether women were taking tamoxifen or anastrozole.