title: Clinical, pathological, proliferative and molecular responses associated with neoadjuvant aromatase inhibitor treatment in breast cancer.
abstract: Neoadjuvant treatment provides an exceptional setting in which to monitor clinical, pathological, proliferative and molecular responses to aromatase inhibitors. Sequential measurements of the primary tumour provide an accurate assessment of clinical changes and the relatively easy access to the tumour within the breast means that biopsies are available for histological and molecular measurements before and during treatment. Large randomised trials (P024 and IMPACT) together with informative non-randomised studies have demonstrated clinical responses to third generation aromatase inhibitors in 40-70% of ER-positive tumours, rates generally significantly higher than observed with tamoxifen. Pathological responses in terms of reduced cellularity/increased fibrosis are also seen in 65-75% of cases. Whilst these are more often seen in clinically responding tumours, the correlation between clinical and pathological response is not absolute. A marked feature of treatment with third generation inhibitors is a reduction in cellular proliferation. Using Ki67 as a marker, this may be observed as early as 10-14 days into treatment. Reduction in proliferation with treatment may be seen in both clinically responding and non-responding tumours, although incidence and degree of effect are higher in responding cases. Aromatase inhibitor treatment frequently fails to reduce proliferation in tumours over-expressing HER-2. In terms of molecular events, aromatase inhibitor treatment is associated with changes in expression of genes classically associated with oestrogen regulation (KIAA0101, ZWINT, IRS1 and TFF1) and cell cycle progression, most notably mitotic phase proteins (CDC2, CCNB1 and CKS2). Changes occur both in clinically responding and non-responding tumours. Although expression of no individual gene correlates absolutely with response status, expression signatures can be produced which distinguish between responding and non-responding tumours. In terms of gene ontology, terms relating to macro-molecular biosynthesis, translation and structural components of ribosomes are significantly enriched. Finally, molecular signatures can be used to illustrate the relative homogeneity of responding tumours and the disparate nature of non-responding tumours suggesting multiple and diverse pathways associated with resistance.
authors.affiliation: Breast Unit Research Group, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom. w.r.miller@ed.ac.uk
authors.forename: W R
authors.initials: WR
authors.lastname: Miller
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D005260:Female; D006801:Humans; D020360:Neoadjuvant Therapy
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors