JAMA Oncol. 2017;3(11):1503-1510. doi:10.1001/jamaoncol.2017.1261.
Laura J. Esserman, MD, MBA; Christina Yau, PhD; Carlie K. Thompson, MD; Laura J. van ‘t Veer, PhD; Alexander D. Borowsky, MD; Katherine A. Hoadley, PhD; Nicholas P. Tobin, PhD; Bo Nordenskjöld, MD, PhD; Tommy Fornander, MD, PhD; Olle Stål, PhD; Christopher C. Benz, MD; Linda S. Lindström, PhD
Importance: The frequency of cancers with indolent behavior has increased with screening. Better tools to identify indolent tumors are needed to avoid overtreatment.
Objective: To determine if a multigene classifier is associated with indolent behavior of invasive breast cancers in women followed for 2 decades.
Design, Setting, and Participants: This is a secondary analysis of a randomized clinical trial of tamoxifen vs no systemic therapy, with more than 20-year follow-up. An indolent threshold (ultralow risk) of the US Food and Drug Administration–cleared MammaPrint 70-gene expression score was established above which no breast cancer deaths occurred after 15 years in the absence of systemic therapy. Immunohistochemical markers (n = 727 women) and Agilent microarrays, for MammaPrint risk scoring (n = 652 women), were performed from formalin-fixed paraffin-embedded primary tumor blocks. Participants were postmenopausal women with clinically detected node-negative breast cancers treated with mastectomy or lumpectomy and radiation enrolled in the Stockholm tamoxifen (STO-3) trial, 1976 to 1990.