Tamoxifen response in premenopausal breast cancer by molecular subtypes in a randomized trial with long-term follow-up

In the present project we aim to identify premenopausal patients by molecular profiling included in a randomized trial of adjuvant tamoxifen versus no adjuvant therapy for improved risk stratification based on gene expression. The randomized study design enables definition of molecular subgroups and profiles for tamoxifen response, stratifying patients into responders versus non-responders. Molecular tests are internationally introduced in clinical decision making for postmenopausal patients with hormone responsive tumors, especially for patients at intermediate risk in whom chemo-endocrine therapy is questionable. For premenopausal patients, however, there is hitherto lack of evidence on the clinical utility of these tests for selection of adjuvant therapy in hormone responsive breast cancer. The present study will add important evidence in the field, based on data from a randomized trial with long-term follow-up data, which will greatly improve the amount and quality of data on molecular tests for guidance on adjuvant hormonal therapy also for premenopausal patients and facilitate forthcoming implementation.