IBIS-II DCIS is investigating whether a drug called anastrozole is more effective than tamoxifen, at preventing new cancers, both in the breast affected by ductal carcinoma in-situ (DCIS) and in the opposite (contralateral) breast.
3980 women from 238 centres in 17 countries have enrolled to take part. The trial closed for recruitment in January 2012. Participants are on treatment for 5 years, after which time their health is followed up for a number of years.
IBIS-II Prevention is investigating whether anastrozole can help prevent breast cancer in women who are at high-risk of the disease. The trial recruited 3864 women from 149 centres in 16 countries and it closed for recruitment in January 2012. Participants are on treatment for 5 years, after which time their health is followed up for a number of years.
The first planned analysis were presented at the San Antonio Breast Cancer symposium in December 2013 and in The Lancet.
The results are very positive - participants being treated with anastrozole being 53% less likely to develop breast cancer than those on placebo. There were 40 cases of breast cancer reported in the anastrozole group compared with 85 in the placebo group.
Although women on anastrozole suffered more joint, bone and muscle aches and more hot flushes, these side effects were less than expected in comparison to other research studies on anastrozole and only slightly more common than for women on placebo.
First results for IBIS-II DCIS are expected to be published in 2015.
More information on the IBIS-II Website.