13 December 2019

For women at high risk for breast cancer, tamoxifen and raloxifene have both been shown to be effective in reducing risk by approximately 30-40%. A recent small study found that low dose (5mg) of tamoxifen is also effective for risk reduction.

In post-menopausal women with a history of breast cancer, it is known that anastrozole (Arimidex), an aromatase inhibitor, is more effective than tamoxifen in terms of reducing breast cancer recurrence. Anastrozole can also be used in high risk women to decrease the likelihood of breast cancer developing, but there is not as much data as we have for tamoxifen.

Updated results of the International Breast Cancer Intervention Study II (IBIS II)* were presented at the San Antonio Breast Cancer Symposium and published in The Lancet. This study compared 5 years of anastrozole versus placebo in post-menopausal women who were at elevated risk for breast cancer. 3864 women were included. After median follow up of 10.9 years, there were 85 breast cancer cases in the anastrozole group versus 165 in the placebo group, a 49% reduction. The “number (of patients) needed to treat” to prevent one breast cancer is 29. There were no differences in deaths. Interestingly, there was also a significant decrease in non-breast cancers in the anastrozole group (147 vs 200), primarily non-melanoma skin cancers. There was no increase in fractures or cardiovascular disease in patients taking anastrozole compared with placebo.

This study shows that as is the case for treatment of breast cancer in post-menopausal women, anastrozole is more effective than tamoxifen for risk reduction. However, side effects of anastrozole are well known (most commonly hot flashes, vaginal dryness, bone / joint pains, and osteoporosis), and may prevent some women from starting or completing a 5-year course of risk-reducing treatment. Women who are at high risk for breast cancer should also be aware of the increased screening (MRI in addition to mammogram) that is often recommended, and all women should understand the influence of lifestyle factors on breast cancer risk, including regular exercise, moderation in alcohol intake, following a healthy diet, and maintenance of an ideal body weight.

ASCO Post: Dr. Jack Cuzick IBIS II 10-year results

Risk Reducing Medications

*If you are not able to access the full study and would like a copy, please email me: contact at drattai dot com

13 May 2019

Note – the survey closed on July 7th 2019. Thank you to all who participated and shared, and we will be sure to post the results when they are available!

Approximately 25-30% of patients with breast cancer who are prescribed endocrine therapy do not complete the full course of treatment, and some patients never start. Side effects of endocrine therapy are well documented but there is very little literature on the role of the medical team in helping patients manage treatment-related side effects. 

This survey is being conducted for research purposes. It is a UCLA research survey, open to women and men with a history of breast cancer who have been treated with or who have received a recommendation for endocrine therapy. 

This survey is voluntary and is completely anonymous – no identifying information, including internet protocol (IP) addresses, will be collected. The survey should take approximately 15 minutes to complete. We value your time and your opinions. 

For questions regarding this study, you may contact principal investigator Dr. Deanna Attai By phone: (818) 333-2555; by email:; or by mail: 191 S. Buena Vista #415, Burbank, CA 91505

UCLA Office of the Human Research Protection Program (OHRPP):
If you have questions about your rights as a research subject, or if you have concerns or suggestions and you want to talk to someone other than the researchers, you may contact the UCLA OHRPP  By phone: (310) 206-2040; by email:; or by mail: Box 951406, Los Angeles, CA  90095-1406

Research Survey Link