Abstract
PurposeThe Ki-67 labelling index is significant for the management of breast cancer. However, the concordance of Ki-67 expression between preoperative biopsy and postoperative surgical specimens has not been well evaluated. This study aimed to find the correlation in Ki-67 expression between biopsy and surgical specimens and to determine the clinicopathological risk factors associated with discordant values.Patients and MethodsKi-67 levels were immunohistochemically measured using paired biopsy and surgical specimens in 310 breast cancer patients between 2008 and 2013. ΔKi-67 was calculated by postoperative Ki-67 minus preoperative levels. The outliers of ΔKi-67 were defined as [lower quartile of ΔKi-67–1.5 × interquartile range (IQR)] or (upper quartile + 1.5 × IQR) and were evaluated according to clinicopathological parameters by logistic regression analysis.ResultsThe median preoperative and postoperative Ki-67 levels were 10 (IQR, 15) and 10 (IQR, 25), respectively. Correlation of Ki-67 levels between the two specimens indicated a moderately positive relationship (coefficient = 0.676). Of 310 patients, 44 (14.2%) showed outliers of ΔKi-67 (range, ≤-20 or ≥28). A significant association with poor prognostic factors was found among these patients. Multivariate analysis determined that significant risk factors for outliers of ΔKi-67 were tumor size >1 cm, negative progesterone receptor (PR) expression, grade III cancer, and age ≤35 years. Among 171 patients with luminal human epidermal growth factor receptor 2-negative tumors, breast cancer subtype according to preoperative or postoperative Ki-67 levels discordantly changed in 46 (26.9%) patients and a significant proportion of patients with discordant cases had ≥1 risk factor.ConclusionKi-67 expression showed a substantial concordance between biopsy and surgical specimens. Extremely discordant Ki-67 levels may be associated with aggressive tumor biology. In patients with luminal subtype disease, clinical application of Ki-67 values should be cautious considering types of specimens and clinicopathological risk factors.
Highlights
Ki-67 is of clinical interest for potential uses in the management of breast cancer patients [1]
Multivariate analysis determined that significant risk factors for outliers of ΔKi-67 were tumor size >1 cm, negative progesterone receptor (PR) expression, grade III cancer, and age 35 years
Ki-67 expression showed a substantial concordance between biopsy and surgical specimens
Summary
Ki-67 is of clinical interest for potential uses in the management of breast cancer patients [1]. It is informative for classification of breast cancer subtypes, may play a predictive role, and is useful in monitoring the response to neoadjuvant therapy [2,3]. In 2007, the American Society of Clinical Oncology (ASCO) updated its recommendations for the use of tumor markers in breast cancer and pointed out that immunohistochemically detected proliferation markers including Ki-67 should not be recommended for clinical practice because of an insufficient level of evidence and a lack of standardization of assay reagents, procedures, and scoring [6]. Similar to other immunohistochemically detected biomarkers, the measurement of Ki-67 by immunohistochemistry has methodological variability regarding preanalytical, analytical, and postanalytical issues [7]. Among various factors that can affect Ki-67 immunohistochemistry, the type of biopsy may not be an important methodological issue and samples from both core biopsy and surgical resection can be suitable [7]
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