 2590 women with primary breast cancer will be recruited in this study from several locations in the United Kingdom and Germany. Eligible patients will be randomly allocated a treatment group, which can be celecoxib or placebo. Both treatments are taken orally celecoxib 400mg daily, placebo 2 tablets daily for a total of 2 years. In addition, hormone receptor positive patients will receive endocrine treatment as per local practice. Patients will prematurely discontinue treatment with celecoxibplacebo if disease progression is confirmed or if patients experience unacceptable toxicity. 