RT Journal Article SR Electronic T1 The Long and Winding Road for Breast Cancer Biomarkers to Reach Clinical Utility JF Clinical Cancer Research JO Clin Cancer Res FD American Association for Cancer Research SP 5543 OP 5545 DO 10.1158/1078-0432.CCR-20-2451 VO 26 IS 21 A1 Hunter, Natasha B. A1 Kilgore, Mark R. A1 Davidson, Nancy E. YR 2020 UL http://clincancerres.aacrjournals.org/content/26/21/5543.abstract AB Tumor data from the ABCSG 5 trial of chemotherapy versus endocrine therapy for premenopausal ER+ breast cancer supports molecular subtyping by Ki-67 IHC as a prognostic marker. But while this tissue was handled uniformly, Ki-67 testing overall is unstandardized, complicating clinical utility. Increasing potential biomarkers herald more challenges in biomarker validation.See related article by Bago-Horvath et al., p. 5682