Significance and problems in evaluations of pathological responses to neoadjuvant therapy for breast cancer

Neoadjuvant therapy consists of systemic drug treatments before surgery for a primary cancer. Currently, several neoadjuvant therapy regimens for breast cancer that use various cytotoxic as well as endocrine-therapeutic and molecular-targeting agents have been performed in clinical practice and/or studies. In neoadjuvant therapy, pre-treatment pathological examination using materials obtained by a core needle biopsy (CNB) is necessary, and pathological diagnosis and evaluation of the biological status, such as hormone receptors and HER-2 over-expression are confirmed. In addition, CNB in the inter-phase of chemotherapy is also thought to be useful for assessment of therapeutic effects before regimens have been completed. After surgery, the therapeutic effects of neoadjuvant therapy have been mainly evaluated on the basis of pathological findings and a pathological complete response (pCR) is considered to be the main target of neoadjuvant therapy. Results of most of clinical studies including NSABP protocol B-18 and B-27 have confirmed the prognostic significance of pCR in neoadjuvant therapy and indicated the significance of pathological evaluation. However, universally accepted pathological response criteria have not been established, but evaluations of the main invasive tumor, intraductal components and regional lymph nodes are thought to be necessary. Additionally, evaluation of the effects below pCR also need examining in a study using a mild anti-cancer drug, such as hormone-therapeutic agent, and the survival outcomes of patients below pCR need to be examined and compared between each grade.