30 March 2007



To evaluate the treatment with the drug anastrozole compared to tamoxifen for women with hormonally sensitive ductal carcinoma in situ (DCIS).

Scientific Title

ANZO2P: An international multi-centre trial of anastrozole vs placebo in postmenopausal women at increased risk of breast cancer and tamoxifen vs anastrozole in postmenopausal women with hormone sensitive ductal carcinoma insitu


Ductal carcinoma in situ (DCIS) was once a rare diagnosis, but it has become increasingly common following the advent of mammographic breast screening. DCIS is a very early stage of breast cancer.  It is also known as non-invasive breast cancer, as the cancer cells are present only in the ducts of the breast and have not spread to other breast tissue or to other parts of the body.

The appropriate treatment for this disease has now become an increasingly important issue. It is generally agreed that adequate local treatment comprises either mastectomy or local excision with clear margins (with or without radiotherapy).

Invasive breast cancer (which means that the cancer cells have spread outside of the breast ducts) has been successfully treated for many years with hormonal drugs such as tamoxifen and anastrozole.  These drugs reduce the amount of oestrogen in the body (oestrogen is one of the female hormones), and this has been shown to have a beneficial effect in women with certain types of breast cancer.  In some women, the drugs can prevent the breast cancer returning and new breast cancers forming in the opposite breast.

In earlier clinical trials where women with DCIS have been given tamoxifen, the results have shown a reduction in the number of women whose DCIS progressed into invasive breast cancer.  However, further research is needed to determine which particular groups of women with DCIS will benefit from taking tamoxifen.  Note there are different types of DCIS ranging in size and level of aggressiveness and other factors.

The IBIS II DCIS study will find out whether anastrozole is as effective, or better than, tamoxifen in preventing the development of breast cancer in the same breast as the DCIS or in the opposite breast, in postmenopausal women who have been diagnosed with DCIS.  The study will also compare the effects (good and bad) of tamoxifen and anastrozole.