A new gold standard in treatment for the majority of women with breast cancer has emerged following the publication yesterday of the world's largest breast cancer trial.
The research was carried out on 9,366 women including 42 from the Republic.
Anastrazole - marketed under the trade name Arimidex - has been shown to prevent more cases of breast cancer recurrence than the current standard therapy, tamoxifen.
The results of the five-year ATAC (Arimidex, tamoxifen, alone or in combination) trial, which were announced yesterday at the annual San Antonio Breast Cancer symposium in Texas, show that anastrazole is more effective than tamoxifen in preventing breast cancer recurrence in post-menopausal women newly diagnosed with early breast cancer.
Post-menopausal women with breast cancer which has been shown to be positive for oestrogen receptors account for about 75 per cent of newly diagnosed cases.
While tamoxifen has been successfully used for 30 years as a long-term treatment to prevent recurrence in women, the results of yesterday's research mean that it will now be supplanted by anastrazole as the drug of first choice.
Women who completed five years' treatment with anastrazole were found to have an additional 26 per cent further reduction in the risk of breast cancer recurrence compared with women taking tamoxifen. The new drug was found to be especially effective in preventing breast cancer spreading to the other breast.
The lead investigator for the study here, Prof Tom Gorey, consultant surgeon at Dublin's Mater Hospital, said: "This is the most compelling evidence that we have seen, so far, to indicate that Arimidex can replace tamoxifen as the treatment standard to protect Irish women from their breast cancer recurring."
He described anastrazole as the "new gold standard" in the adjuvant treatment (treatment to suppress secondary tumour formation) of breast cancer.
Asked what his advice to the many women currently taking tamoxifen would be, Prof Gorey said they should remain on tamoxifen until their next routine appointment.
He pointed out that a related clinical trial, the results of which were also published yesterday, had found that if women changed to anastrazole two to three years after starting tamoxifen, they had a 41 per cent lower risk of their cancer returning.
In absolute terms, eight in every 100 women who receive no hormonal therapy will experience a recurrence of breast cancer within five years. With tamoxifen, this risk was lowered to four in 100 women experiencing a recurrence.
Anastrazole reduces the risk further, so that two in 100 women will experience a recurrence up to five years after diagnosis, while taking the latest treatment.
According to the latest statistics from the National Cancer Registry there are 1,700 new cases of breast cancer diagnosed in the State each year.
Almost 80 per cent of women with breast cancer are alive five years after diagnosis. Most women have surgery combined with radiotherapy, chemotherapy or both as first line treatment for the condition. Hormonal agents such as anastrazole and tamoxifen are then used in the majority of women to prevent the long-term recurrence of the cancer.