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IBIS-II is an international multi-centre breast cancer prevention study that is split into prevention and DCIS components.

IBIS-II Prevention is studying the use of anastrozole versus placebo in postmenopausal women at increased risk of breast cancer. It aims to determine whether anastrozole can help prevent breast cancer in these patients.

IBIS-II DCIS is investigating the effects of tamoxifen versus anastrozole in postmenopausal women with Ductal Carcinoma in Situ (DCIS). It aims to determine which breast cancer treatment drug, anastrozole or tamoxifen, is better at preventing the disease from returning in women who have had DCIS.

The study started accruing patients in February 2003 with an initial combined target of 10000 patients for both studies, 6000 for prevention and 4000 for DCIS (as there were more events than originally anticipated the target for Prevention was later recalculated to be 3500).

IBIS-II has now closed to recruitment. In total 6844 women worldwide joined this important study (3864 in Prevention and 2980 in DCIS). The Steering Committee (blinded to outcome) and Data Monitoring Committee (unblinded) have reviewed the status of the trial and neither favours an early report of the results. Analysis is currently planned for when the median follow-up is 5 years, which will be in 2013.
Coordinating group: IBIS-II

Patients accrual
Start date: February 2003
Closure date: January 2012

Target nr. of patients: 3500
Final accrual: 3864

Target nr. of patients: 4000
Final accrual: 2980

IBIS-II (Prevention + DCIS)
Target nr. of patients: 7500
Final accrual: 6844

Reason for closure: Reached target accrual

DCIS Identifier: NCT00072462
Prevention Identifier: NCT00078832

For more information about this trial visit