Systemic therapy for early-stage breast cancer: learning from the past to build the future

The treatment of breast cancer has improved dramatically over the past century, from a strictly surgical approach to a coordinated one, including local and systemic therapies. Systemic therapies for early-stage disease were initially tested against observation or placebo only in adjuvant trials. Subsequent clinical trials focusing on treatment 'fine-tuning' had a marked increase in cohort size, duration and costs, leading to a growing interest in the neoadjuvant setting in the past decade. Neoadjuvant trial designs have the advantages of enabling the direct evaluation of treatment effects on tumour diameter and offer unique translational research opportunities through the comparative analysis of tumour biology before, during and after treatment. Current technologies enabling the identification of better predictive biomarkers are shaping the new era of (neo)adjuvant trials. An urgent need exists to reinforce collaboration between the pharmaceutical industry and academia to share data and thus establish large databases of biomarker data coupled with patient outcomes that are easily accessible to the scientific community. In this Review, we summarize the evolution of (neo)adjuvant trials from the pre-genomic to the post-genomic era and provide critical insights into how neoadjuvant studies are currently designed, discussing the need for better end points and treatment strategies that are more personalized, including in the post-neoadjuvant setting.