In the current study, we evaluated the prognostic and predictive potential of Ki-67 in TNBC. However, the importance and the best cutoff point of this marker as a prognostic and predictive factor in TNBC remains unclear. The Ki-67 cutoff at 14% is an important parameter in subclassifying luminal BC into the luminal A subtype with good prognosis and the luminal B subtype with worse prognosis 6, 7, 8. Currently, Ki-67 is principally used to evaluate prognosis, guide adjuvant treatment and predict the response to neoadjuvant treatment in ER+/HER2− BC. In a study conducted by Cheang 5, the cutoff value for the immunohistochemically determined Ki-67 index to distinguish luminal B from luminal A BC was 13.25%, while some panels showed that a threshold of ≥20% was clearly indicative of ‘high’ Ki-67 status 6. In general, high levels of Ki-67 expression in BC correlate strongly with more tenacious proliferation and poor prognosis. As one of the most widely used immunohistochemistry (IHC) proliferation antigens, Ki-67 has been proposed to be a measure for the quantification of cell proliferation in BC samples 4. Ki-67 is a protein expressed in the nucleus of cells during different phases of the cell cycle, except in the G0 quiescent state. Among these new biomarkers, Ki-67 is one of the most promising markers.

Recently, a new panel of biomarkers has been identified to provide both prcognostic and predictive information for BC. The prognostic factors for BC include histological features (histological type, histological grade, and lymphovascular invasion), lymph node status, tumor size, steroid hormone receptor status and age 3. The expression of biomarkers is one of the important factors for treatment strategy decision-making. Therefore, TNBC has poor prognosis and worse survival 1, 2. A higher recurrence rate and a higher frequency of metastasis are often observed in more biologically aggressive TNBCs in contrast with other subtypes. Compared to other BC subtypes, patients with TNBC currently cannot benefit from targeted therapy or endocrine therapy. Triple-negative breast cancer (TNBC) accounts for approximately 15% of all breast cancers (BCs) and lacks estrogen receptor (ER) and progesterone receptor (PR) expression as well as human epidermal growth factor receptor 2 (HER2) amplification. For stage I/Ki-67 low TNBC patients, the advantage of CT is unclear, providing the basis for future de-escalation therapy. In multivariate analyses, N-stage ( p 30% was significantly associated with worse prognosis, especially for stage I patients. At the cutoff point of 30%, worse DFS and OS were observed in the Ki-67 high group. The most relevant cutoff value for Ki-67 for prognosis was 30% ( p = 0.008). Overall survival (OS) and disease-free survival (DFS) were compared between the two groups using the Kaplan-Meier method and Cox regression model. Propensity score matching (PSM, ratio = 1:2) was performed to match the Ki-67 low group with the Ki-67 high group. The optimal cutoff for Ki-67 was assessed by Cutoff Finder. However, the importance and the best cutoff point of Ki-67 in triple-negative breast cancer (TNBC) remains unclear and was evaluated in this study.A total of 1800 patients with early invasive TNBC between 20 at Fudan University Shanghai Cancer Center were consecutively recruited for this study. As a cell proliferation biomarker, Ki-67 is principally used in ER+/HER2− breast cancer.

Triple negative breast cancer prognosis