EndoPredict® Extended Endocrine Trial (EXET)

The EndoPredict® molecular test is validated to predict late distant recurrence after 5 years of endocrine therapy in women with estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2-) early stage breast cancer, with or without treatment with adjuvant chemotherapy. The test provides an individualized EPclin score based on the tumor gene expression, tumor size and nodal status, and categorizes patients as High or Low risk of distant recurrence. The primary objective of this study is to evaluate the distant recurrence-free survival (DRFS) at 5-10 years in patients with ER+/HER2- early stage breast cancer with EPclin Low scores that did not extend endocrine therapy. Data collection is prospective and patient enrollment is expected to occur over 24 months. The study will enroll patients who are near the 5-year post-diagnosis time point when decisions on extending endocrine therapy are being made. Patient breast cancer tumors, stored from surgical collection after initial diagnosis, will be tested with EndoPredict and a report generated. The provider will convey the report results to the patient and establish a treatment plan to continue or forgo endocrine therapy. Patients will then be followed for 6 years with data collection every year, and outcomes (distant and local disease recurrence, second primary breast cancer, etc.) recorded. The associations between outcomes and treatment, EPclin score and risk category, EP molecular score, and clinicopathologic features will be investigated in all patients and in subpopulations (node negative, node positive, treated with or without chemotherapy, etc.).