TAMOXIFEN REDUCES BREAST CANCER RATES

New analysis of the breast cancer drug tamoxifen shows that the preventive effect of the drug continues for 20 years, after treatment with the drug has stopped, with breast cancer rates reduced by around 30%.

The new and extended analysis of the IBIS-I clinical trial (International Breast Cancer Intervention Study) were announced at the San Antonio Breast Cancer Symposium in Texas, USA, and published in The Lancet Oncology.

IBIS-I was conducted in Australia and New Zealand by the Australia and New Zealand Breast Cancer Trials Group (ANZBCTG) and coordinated internationally by Cancer Research UK. More than 7,100 women worldwide participated in the clinical trial, including 2,600 women from 22 institutions in Australia and New Zealand.

The IBIS-I clinical trial examined the long-term risk and benefits of taking tamoxifen to prevent breast cancer in women at high risk of the disease (aged 35-70 years and with a family history of breast cancer such as mother or sister). As part of the study, pre and post-menopausal women were randomised to receive either tamoxifen or a matching placebo for five years. After completing treatment, the health of all participants was monitored with an average follow-up time of 16 years and maximum of 22 years.

The results of the long term analysis found that 251 women from the tamoxifen group versus 350 women from the placebo group developed breast cancer, which is a reduction of 29%. Oestrogen receptor (ER) positive breast cancer (which accounts for two third of all breast cancers) was reduced by 35%. After 20 years of follow up, the estimated risk of developing breast cancer was 8% in the tamoxifen group, compared to 12% in the placebo group.

Professor John Forbes AM is the Director of Research at the ANZBCTG and the IBIS-I Study Chair. He is Professor of Surgical Oncology at the University of Newcastle and Director of Surgical Oncology at the Calvary Mater Newcastle Hospital. Professor Forbes thanked the women who have participated in the IBIS-I clinical trial.

“The participation of women in this important research has enabled scientists to advance prevention strategies and treatments available to all women who are at risk of or diagnosed with breast cancer. Over the last 20 years, we have seen a significant fall in breast cancer mortality rates,” Professor Forbes said.

“We know that tamoxifen is a well-established prevention drug for certain breast cancers. This analysis provides evidence of the long-term benefits of tamoxifen in women at high risk of the disease and IBIS-I has led to new recommendations for the care of women.

“Since we first started recruiting women to the IBIS-I clinical trial in Australia and New Zealand in 1992, women now have a number of options for the prevention of breast cancer. For most pre-menopausal women at high risk of the disease, this analysis shows that tamoxifen remains a good choice.

“This research also demonstrates how important long-term analysis is. We still need to monitor women who participated in IBIS-I to examine the impact of tamoxifen on death rates and the side-effects of this prevention drug, particularly the increased occurrence of endometrial cancer.

The long-term results of the IBIS-I clinical trial comes one year after the first results of the IBIS-II clinical trial were announced. IBIS-II found that taking the breast cancer drug anastrozole (an aromatase inhibitor) for five years reduced the chances of post-menopausal women at high risk of developing the disease by 53% compared to women who took a placebo.

The ANZBCTG is Australia’s national organisation dedicated entirely to breast cancer research. It conducts a national clinical trials research program for the treatment, prevention and cure of breast cancer. The research program involves multicentre clinical trials and collaboration with 87 institutions and over 700 researchers throughout Australia and New Zealand and many more globally. More than 14,000 women have participated in ANZBCTG breast cancer clinical trials. The fundraising department of the ANZBCTG is the Breast Cancer Institute of Australia (BCIA).

The IBIS-I clinical trial has received project support from the National Health and Medical Research Council.

Media contact:

Anna Fitzgerald,

ANZBCTG Communications Manager

Phone: 02 4925 5255 or 0400 304 224

Email: anna.fitzgerald@anzbctg.org