INTRODUCTION: The use of chemotherapy in node-negative, (O)Estrogen Receptor 
(ER)-positive breast cancer has changed significantly since the introduction of 
Oncotype DX to determine systemic recurrence risk based on tumour genomic 
signature.
AIMS: This study aims to
METHODS: A cohort study was undertaken, including consecutive patients with 
early node-negative, ER-positive breast cancer diagnosed between 2006 and May 
2013, including a period of prospective clinical trial (Trial Assigning 
Individualised Options for Treatment (TAILORx)) recruitment. Data were collected 
regarding patient demographics, tumour clinico-pathological features, Oncotype 
DX use and recurrence score and chemotherapy use. All therapeutic decisions were 
made following multidisciplinary discussion, with adherence to guidelines and 
consideration of trial protocol and Oncotype DX recurrence scores.
RESULTS: 479 consecutive patients were included in the study, of whom 241 (50%) 
underwent Oncotype DX testing, 97 as part of the TAILORx clinical trial. 
Oncotype DX testing began on a trial basis in 2007 and until October 2011, only 
patients enrolled on TAILORx availed of genomic profiling. From October 2011, 
Oncotype DX was used in all eligible patients as per National Cancer Control 
Programme (NCCP) guidelines. A total of 216 (45%) patients received 
chemotherapy. The use of chemotherapy changed in inverse proportion to the 
availability of the genomic assay. Of those patients in whom Oncotype DX was 
utilised, 138 (57%) were spared chemotherapy.
CONCLUSION: This study validates the use of molecular testing in the 
rationalisation of systemic therapy.