Association of Circulating Tumor Cells With Late Recurrence of Estrogen Receptor–Positive Breast Cancer

Abstract

Breast cancer is the most common cancer and the leading cause of death from cancer among women, accounting for 25% of all cancers and 15% of deaths from cancer worldwide.^1,2 Although most patients with breast cancer present with localized disease that is potentially curable with surgery and radiation,³ recurrence in distant organs is common and incurable.⁴ Adjuvant systemic therapies reduce distant recurrence and breast cancer mortality.⁵ Adjuvant chemotherapy reduces recurrence primarily within 5 years after diagnosis,⁶ whereas endocrine therapy reduces recurrence during a typical 5-year treatment course and after completion of endocrine therapy because of a carry-over effect.^7,8 Recurrence 5 years or more after a diagnosis is commonly referred to as late recurrence and accounts for approximately one-half of all recurrences of hormone receptor–positive breast cancer, whereas recurrence 5 years or more after diagnosis is considerably less common among patients with hormone receptor–negative disease.^9,10 Continuing tamoxifen therapy beyond 5 years or switching to an aromatase inhibitor are associated with reductions in recurrence and breast cancer mortality,^11-14 whereas continuing therapy with aromatase inhibitors beyond 5 years is associated with marginal effects in reducing distant recurrence risk.^15-17