Identifying biomarkers to select patients with early breast cancer suitable for extended adjuvant endocrine therapy

In this review, we summarize recent and current biomarkers and assays that are being considered in the selection of suitable patients with estrogen receptor-positive early breast cancer for extended (years 5-10) adjuvant endocrine therapy (AET).

Women with estrogen receptor-positive early-stage breast cancer (65% of cases) continue to have late risk for distant recurrence extending beyond 5 years from surgery. Recent large trials have consistently demonstrated improvement for prolonging endocrine therapy. However, endocrine therapy can cause women bothersome side effects and can negatively impact quality of life. Determining which patients remain at risk for disease recurrence and predicting which of these patients would derive the most benefit from the addition of extended AET are key issues faced by patients and oncologists today. A number of predictive molecular assays have been developed and are being considered as tools to be used in guiding the implementation of adjuvant systemic therapy.

The future holds much promise and as more information and understanding is acquired, treatment regimens will increasingly incorporate clinically validated biomarker assays in the decision-making process that will be of great benefit to these patients. Proving clinical utility, though, will ultimately decide their implementation.