Additional value and potential use of the 70-gene prognosis signature in node-negative breast cancer in daily clinical practice

Background: The 70-gene prognosis signature has strong prognostic value in node-negative breast cancer, independent of established prognostic factors. It is unclear whether all node-negative patients should receive a signature result. We therefore evaluated its additional prognostic information to a combination of established prognostic guidelines. Methods: We evaluated 701 patients from three previously described series in whom a signature result was available. Clinical risk was on the basis of Adjuvant! Online (AO), St Gallen guidelines (St G) and Nottingham Prognostic Index (NPI). Overall survival (OS) analyses were carried out in patients treated at the Netherlands Cancer Institute (Amsterdam) who did not receive adjuvant systemic treatment (AST). Results: Only 6% (10 of 156) of estrogen receptor (ER)-negative tumours had a good prognosis signature. The signature was not useful for ER-positive tumours and concordant high AO, high St G and/or high NPI clinical risks (N = 139). The 10-year OS estimate for good signature tumours with these characteristics was <80% and AST would therefore be appropriate irrespective of the signature result. In contrast, for patients with a concordant low AO, low St G and/or low NPI risk and in discordant clinical risk patients, the signature identified low-risk patients in whom AST could be safely withheld (10-year OS > 90%). Conclusion: The 70-gene prognosis signature provides additional prognostic information especially in ER-positive lymph node-negative breast cancer patients with a predominant low or discordant clinical risk on the basis of AO, St G and/or NPI.