Personalized adjuvant therapies: lessons from the past: the opening address by the St. Gallen 2013 award recipient.

For several decades, personalized adjuvant therapies have been prescribed based on features that predict response to specific types of treatment. In this summary four specific issues regarding adjuvant therapies are described. Each one developed using information from past experience and is ready to be challenged by future findings from clinical trials and maturation of follow-up data. 1) Accuracy of determination of steroid hormone receptors and of HER2-status was the key feature in International Breast Cancer Study Group (IBCSG) and Breast International Group (BIG) trials. 2) Investigations on ovarian function suppression in IBCSG clinical trials led to the design of two trials (SOFT and TEXT), which are likely to lead to improved adjuvant therapy for premenopausal women with breast cancer. 3) Data from the BIG 1-98 trial of letrozole vs tamoxifen for postmenopausal patients with endocrine-responsive breast cancer provided information on which patients might obtain increased benefit from aromatase inhibitors and which might achieve similar treatment outcome with tamoxifen alone. 4) Finally, low-dose, frequently administered cytotoxics (metronomic chemotherapy) were tested in advanced disease with surprisingly favorable disease control and very low incidence of side effects. Personalized treatments are likely to improve substantially with increasingly accurate determination of their targets and by using risk- and toxicity-modulated therapies.