Limited Adjuvant Endocrine Therapy for Low Risk Breast Cancer

Women older than 50 at diagnosis of an invasive breast cancer which is all of: node negative/N0i+; T1 or T2; low or intermediate grade; with strong or intermediate expression of hormone receptors (ER and PR); and HER2 negative, and who have had adequate local therapy for their tumor, are invited to participate in Prosigna® screening. A sample of their excised tumor is sent for Prosigna® testing. This is a validated and widely approved genomic test to assess recurrence risk in hormone receptor positive/HER2 negative, node negative breast tumors. Tumors with a low risk result, defined as Risk of Recurrence (ROR) less than or equal to 40, are then eligible for enrollment on the LA LEAST study of 2 years of endocrine therapy (tamoxifen for pre/perimenopausal women and aromatase inhibitor for postmenopausal women). To mimic real life, there is flexibility to switch to an alternate standard of care endocrine therapy during the two years if intolerable side effects develop. During the two years of therapy, participants are seen every six months and complete periodic quality of life (QOL) questionnaires designed to measure quality of life, mood, side effects, and anxiety/fear of recurrence. Following two years of therapy, participants have annual study visits until year 10, with similar questionnaires at some but not all time points, and assessment of study endpoints. Primary endpoint is the 5 year distant relapse free interval (DRFI), defined as freedom from distant recurrence or breast cancer death at five years. Secondary endpoints include longitudinal QOL comparisons, 10 year breast cancer free interval and 10 year contralateral breast cancer rate. It is anticipated that about 400 individuals will need to be screened to enroll 290 participants with requisite low score. The sample size is based on an expected 5 year DRFI of 96.8%, one sided alpha of 0.05 and a rejection of the alternate hypothesis if the lower boundary of the one sided confidence interval yields an observed DRFI below 95%.