Determine whether the Breast Cancer Index BCI (H/I) status (High vs Low) is predictive of the benefit of 10 years versus 5 years of tamoxifen.
Evaluate whether BCI (H/I), as a continuous index, demonstrates a statistically significant treatment to biomarker interaction with extended tamoxifen treatment
Detailed clinical data presentation of using this new dignostic assay we are able to identify a group of 10% of patients who do benefit extending endocrine therapy to 10 years instead of 5 years. This study shows that we can now identify which patients can safely discontinue treatment at 5 years avoiding the risks of side effects. We have reached level 1B evidence and this diagnostic test may be implemented in the clinic.