TREATMENT OPTIONS FOR POSTMENOPAUSAL WOMEN
10/12/2020
Anastrozole and Tamoxifen Both Prevent Breast Cancer for Postmenopausal Women
Long-term follow-up of the IBIS-II DCIS clinical trial has found that Anastrozole and Tamoxifen are both effective in preventing breast cancer and DCIS, providing more treatment options for postmenopausal women with an early form of breast cancer.
The results were announced at the San Antonio Breast Cancer Symposium in the United States. 2,980 women were recruited to the IBIS-II DCIS clinical trial worldwide, including 178 women at 24 institutions in Australia and New Zealand where the study was coordinated by Breast Cancer Trials.
Women who have been diagnosed with Ductal Carcinoma in Situ (DCIS) are at higher risk than the average woman of being diagnosed with DCIS or breast cancer in the future. DCIS is a pre-cancerous change that can progress to breast cancer, where abnormal cells are present in milk ducts, but have not yet spread to the surrounding breast tissue or elsewhere in the body.
Whilst DCIS is not cancer, it may turn into cancer if left long enough, so the mainstay of treatment is surgery to remove it. Radiotherapy and hormone blocking therapy may also be used for some patients. A diagnosis of DCIS or breast cancer and subsequent treatment can be traumatic for patients, and treatments are needed to help prevent a future diagnosis of DCIS or breast cancer.
The IBIS-II DCIS trial aimed to find out if Tamoxifen or Anastrozole was better at preventing breast cancer or DCIS after prior surgical removal of DCIS in postmenopausal women. These two hormone blocking medications are effective in preventing breast cancer from returning, but the role in prevention after DCIS has been less clear. Tamoxifen is now available on the Pharmaceutical Benefits Scheme (PBS) as a preventative medication, but Anastrozole is not.
The IBIS-II trial demonstrated that the two drugs are similarly effective on preventing future DCIS or breast cancer over the 12 years of follow-up of the trial. Interestingly, Anastrozole was more effective whilst taking the medication for 5 years, but after stopping at 5 years, there was no longer a difference compared with Tamoxifen. After 12 years, 9.7% of patients on Tamoxifen and 8.5% of patients on Anastrozole were diagnosed with DCIS or breast cancer. There was no difference in survival between the two drugs.
“An important part of the decision between Tamoxifen and Anastrozole is understanding the side effects, especially when taking them for preventative purposes,” said Breast Cancer Trials Medical Advisor and BCT Study Chair of IBIS-II Dr Nicholas Zdenkowski.
“This trial shows that both drugs are safe to take, with notable differences in the side effects. With Tamoxifen, fewer fractures and strokes were seen. With Anastrozole, there was a lower rate of endometrial and ovarian cancer. This knowledge can assist with guiding patients towards which drug is more suitable for their personal circumstances. It is hoped that Anastrozole will be listed on the PBS for prevention purposes, given the favourable safety and effectiveness profile.”
Breast Cancer Trials is the largest clinical trials research group in Australia and New Zealand and has been conducting clinical trials for more than 40 years. The results have improved the treatment of breast cancer, changed clinical practice and saved lives through research collaboration. The research program brings together almost 800 researchers in 107 institutions throughout Australia and New Zealand. More than 16,000 people have participated in BCT clinical trials.
Contact: Anna Fitzgerald – Breast Cancer Trials Communications Manager
02 4925 5256 or 0400 304 224; anna.fitzgerald@bctrials.org.au
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