The evolution of treatment strategies: Aiming at the target

Historically, the selection of adjuvant systemic therapy in early breast cancer has relied on risk assessment embodied by the TNM classification. Since the 2005 International St. Gallen Consensus, treatment selection now involves firstly identifying critical targets and then using risk to assess the trade-off between anticipated toxicity and efficacy. This evolution in treatment strategies began with the identification of the estrogen receptor, and culminated with the HER2 receptor, with recent astounding success in several adjuvant trials. Newer technologies including gene expression profiles and micrometastases tracking bear exciting potential in refining the treatment strategies further. Alongside the progress in developing agents that target different molecules across the whole breast cancer population, these newer technologies aim to tailor adjuvant treatment further by identifying breast cancer subgroups that may benefit most from being targeted with specific therapy, by defining molecular subtypes, recognizing chemo-sensitivity and resistance, identifying at-risk gene signatures, and by detecting stem cells capable of generating metastases. This paper will review this evolution of treatment strategies, from the lessons learnt from the past, to the exciting promise of tailored therapy of the future