We read with great interest the manuscript of the 13th St Gallen International Breast Cancer Conference (Goldhirsch et al. Ann. Oncol. 2013, 24, 2206-2223). Concerning multi-gene signatures the” 21-gene RS is accepted as providing not only prognostic, but also predictive information regarding the utility of cytotoxic therapy in addition to endocrine therapy for patients with luminal disease.
This is a definite statement, however, we want to draw attention to the fact that this evidence is based on two clinical trials including also HER2-positive breast cancer patients. This inclusion of HER2-positive patients might alter the predictive value of RS in luminal HER2-negative breast cancer patients and we thus consider it important to discuss this issue publicly.