The roles of neoadjuvant therapy both as a standard thera-peutic approach and a research tool are very closely tied andhave yielded insights into both breast cancer biology andnew drug development [1, 2]. From a clinician’s standpoint,however, the key questions that arise revolve around theclinical advantages of neo-adjuvant therapy in terms ofsurgical outcomes, long-term recurrence/mortality anddecision-making. At the current time, the main advantage ofneoadjuvant therapy is to improve the odds of adequatesurgical resection, particularly breast-conserving surgery[3, 4]. Beyond that, long-term outcomes or clinical deci-sion-making do not appear to be affected by the sequence ofsystemic therapy in relation to definitive surgery. It isbecoming clear that breast cancer is heterogeneous. Ge-nomically defined subsets, which map to some extent withhormone and HER2 receptor subtypes, exhibit differentialrecurrence hazard reductions with systemic therapies—andthis concept also applies to neoadjuvant therapy response aswell [5]. But there is also clinical diversity, for example,contrasting rapid onset inflammatory cancer to a moreindolent cancer that has been clinically present for severalyears. Therefore, current neoadjuvant treatment paradigmsmust incorporate the base of evidence from large scaleclinical trials as well as the biological context of the disease.The reports contained in this special issue of Breast CancerResearch and Treatment highlight current trends and resultsthat are shaping both patient care and research in this area.The report by Lin et al.[6] demonstrate biological dif-ferences between interval and screen-detected cancerstreated on a prospective trial, even though the number ofscreening-detected cancers was small, as would be typicalin a neoadjuvant trial where the majority of patients werenot undergoing screening. As expected, interval cancershad a tendency to be hormone receptor-negative and ofhigher grade, whereas screen-detected cancers were all ofthe luminal intrinsic subtypes by gene expression array.Nevertheless, this report points to the need to stratifypatients by known characteristics associated with responsein clinical trials and to use established factors in routineclinical practice. For example, it is now clear that patientswith hormone receptor-positive cancer have less responseto neoadjuvant therapy and lower pathologic completeresponse (pCR) rates. Receptor status might thereforeaffect the decision regarding the timing of chemotherapy,especially if breast-conserving surgery is driving thedecision. Several phenotypes that are also related to hor-mone receptor content, but appear to have independentprognostic factors for response, such as proliferation indexand risk score by gene profile assays are the next markerson the horizon that could enter into this decision-making iftumor size reduction is a main goal of therapy [7, 8].Is there an optimum neoadjuvant regimen? Should non-standard adjuvant regimens that yield high pCR rates beadopted into routine practice? Until neoadjuvant trials arepowered for long-term outcome, at the current time, it isimportant to remember that the most important benefit ofneoadjuvant therapy is its ‘‘adjuvant’’ effect on long-termrecurrence and mortality. Therefore, an evidence-basedapproach would dictate the use of proven standard adjuvantregimens in the neoadjuvant setting. However, trials thatbridge pCR rates in relevant subsets to long-term outcomecould serve as the basis for approvals of new drugs andregimens and eventually shorten regulatory approval times[9]. Some long-standing standards may need to be
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