Abstract
Ki67 is a proliferation marker. It has been proposed as a useful clinical marker for breast cancer subtype classification, prognosis, and prediction of therapeutic response. But the questionable analytical validity of Ki67 prevents its widespread adoption of these measures for treatment decisions in breast cancer. Currently, Ki67 has been tested as a predictive marker for chemotherapy using clinical and pathological response as endpoints in neoadjuvant endocrine therapy. Ki67 can be used as a predictor to evaluate the recurrence-free survival rate of patients, or its change can be used to predict the preoperative “window of opportunity” in neoadjuvant endocrine therapy. In this review, we will elaborate on the role of Ki67 in neoadjuvant endocrine therapy in breast cancer.
Highlights
Ki67 is a nuclear antigen that is an excellent marker of active cell proliferation in the normal and tumor cell populations [1]
Several studies have investigated the possible use of Ki67 assessment in neoadjuvant endocrine therapy (NET)
In IMPACT, the change of Ki67 was greater in the anastrozole group than in the other groups at 2 weeks and 12 weeks, which closely parallels the results of the relative recurrence-free survival with adjuvant endocrine therapy after long follow-up in the ATAC trial in 9,366 patients
Summary
Ki67 is a nuclear antigen that is an excellent marker of active cell proliferation in the normal and tumor cell populations [1] It has been proposed as a useful clinical marker for breast cancer subtype classification, prognosis, and prediction of therapeutic response [2,3,4]. A clinical trial from the European Institute of Oncology indicated that high Ki67 (≥32%) can benefit from adjuvant chemotherapy in luminal B breast cancer with positive lymph node metastasis [30]. Ki67 index is a valuable prognostic indicator in endocrine-responsive breast cancer without lymph node metastasis, but it is not a predictive factor of better response to adjuvant chemotherapy in these studies [30, 34]. IMPACT is a clinical trial similar to the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial, which compared 5 years of the aromatase inhibitor anastrozole alone, tamoxifen
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