Interlaboratory variability of Ki67 staining in breast cancer

BackgroundPostanalytic issues of Ki67 assessment in breast cancers like counting method standardisation and interrater bias have been subject of various studies, but little is known about analytic variability of Ki67 staining between pathology labs. Our aim was to study interlaboratory variability of Ki67 staining in breast cancer using tissue microarrays (TMAs) and central assessment to minimise preanalytic and postanalytic influences.MethodsThirty European pathology labs stained serial slides of a TMA set of breast cancer tissues with Ki67 according to their routine in-house protocol. The Ki67-labelling index (Ki67-LI) of 70 matched samples was centrally assessed by one observer who counted all cancer cells per sample. We then tested for differences between the labs in Ki67-LI medians by analysing variance on ranks and in proportions of tumours classified as luminal A after dichotomising oestrogen receptor–positive cancers into cancers showing low (<14%, luminal A) and high (≥14%, luminal B HER2 negative) Ki67-LI using Cochran's Q.ResultsSubstantial differences between the 30 labs were indicated for median Ki67-LI (0.65%–33.0%, p < 0.0001) and proportion of cancers classified as luminal A (17%–57%, p < 0.0001). The differences remained significant when labs using the same antibody (MIB-1, SP6, or 30-9) were analysed separately or labs without prior participation in external quality assurance programs were excluded (p < 0.0001, respectively).ConclusionSubstantial variability in Ki67 staining of breast cancer tissue was found between 30 routine pathology labs. Clinical use of the Ki67-LI for therapeutic decisions should be considered only fully aware of lab-specific reference values.     

Ki67: a time-varying biomarker of risk of breast cancer in atypical hyperplasia

Uncontrolled proliferation is a defining feature of the malignant phenotype. Ki67 is a marker for proliferating cells and is overexpressed in many breast cancers. Atypical hyperplasia is a premalignant lesion of the breast (relative risk ~ 4.0). Here, we asked if Ki67 expression could stratify risk in women with atypia. Ki67 expression was assessed immunohistochemically by digital image analysis in archival sections from 192 women with atypia diagnosed at the Mayo Clinic 1/1/67–12/31/91. Risk factor and follow-up data were obtained via study questionnaire and medical records. Observed breast cancer events were compared to population expected rates (Iowa SEER) using standardized incidence ratios (SIRs). We examined two endpoints: risk of breast cancer within 10 years and after 10 years of atypia biopsy. Thirty-two (16.7%) of the 192 women developed breast cancer over a median of 14.6 years. Thirty percent (58) of the atypias had ≥2% cells staining for Ki67. In these women, the risk of breast cancer within 10 years after atypia was increased (SIR 4.42 [2.21–8.84]) but not in those with <2% staining. Specifically, the cumulative incidence for breast cancer at 10 years was 14% in the high Ki67 vs. 3% in the low Ki67 group. Conversely, after 10 years, risk in the low Ki67 group rose significantly (SIR 5.69 [3.63–8.92]) vs. no further increased risk in the high Ki67 group (SIR 0.78 [0.11–5.55]). Ki67 appears to be a time-varying biomarker of risk of breast cancer in women with atypical hyperplasia.     

Comparison between Ki67 labeling index determined using image analysis software with virtual slide system and that determined visually in breast cancer

Background

In recent papers, Ki67 labeling index (LI) has been used to classify breast cancer patients into the low and high Ki67LI groups for comparison studies, which showed significant differences in many prognostic factors. It has not been clarified whether image analysis software can be used for calculating LI in breast cancer. In our study, we examined whether Ki67LI in breast cancer calculated using image analysis software correlates with that measured on the basis of visual.

Methods

Fifty patients were randomly selected among breast cancer patients who underwent surgical operation from March, 2010 to May, 2010 in our hospital without preoperative chemotherapy. In this study, for the virtual slide system (VSS: VS120-L100, Olympus, Tokyo, Japan), the high-resolution VSs of all the 50 patients were prepared as samples. The image analysis software use for calculating LI was Tissuemorph Digital Pathology (Tissuemorph DP: Visiopharm, Hoersholm, Denmark). The calculated LI was extracted from 3 to 5 views containing hot spots. The LI calculated using Tissuemorph DP was designed as LI/image/T. The digital image of 3 to 5 LI/image/T views was printed out, and on the digital photograph, we counted visually the number of Ki67-immunopositive cells in exactly the same area, and the percentage of Ki67-immunopositive cells was designed as LI/direct. Moreover, a pathologist’s assistant (PA) determined the tumor area in the same specimen using VSS and calculated LI using Tissuemorph DP, which was designed as LI/image/PA. The chief pathologist (CP) similarly calculated LI which was designed as LI/image/CP. We evaluated the degree of agreement between different data sets “LI/image/T and LI/direct” and “LI/image/T, LI/image/CP, and LI/image/PA” by using interclass correlation coefficient (ICC).

Results

The average counts of cells were as follows: LI/direct, 3209.7 ± 1970.4 (SD); LI/image/T, 2601.6 ± 1697.1; LI/image/PA, 2886.5 ± 2027.5; LI/image/CP, 18805.5 ± 22293.4. The values of LI/direct and LI/image/T showed almost perfect agreement as showed by an ICC of 0.885 (95 % CI, 0.806–0.933; p < 0.001). The agreement among three investigators was almost perfect. The obtained ICC was 0.825 (95 % CI, 0.739–0.890; p < 0.001) among the data of LI/image/T, LI/image/CP and LI/image/PA. There were five cases that immunopositivity for Ki67 showed a more than 10 % disagreement between LI/direct and LI/image/T.

Conclusion

The merits of calculating Ki67 LI using Tissuemorph DP are as follows. First, the staining intensity of the cells to be counted can be adjusted. Second, the portion of a tumor including “hot spots” for counting can be chosen. Third, many cancer cells can be counted more rapidly using Tissuemorph DP than by visual observation. However, it is important that pathologist should check and carry out the final decision of the data, when Ki67 LI using Tissuemorph DP is calculated.

     

Prognostic Significance of the Ki67 Scoring Categories in Breast Cancer Subgroups

BackgroundImmunohistochemical (IHC) expression of Ki67 has a prognostic and predictive value for breast cancer, and the IHC Ki67 labeling index is estimated by counting the number of positive and negative cells. It has not been clarified whether IHC Ki67 estimated using a semiquantitative scoring system has a prognostic value. We aimed to estimate the usefulness of scoring categories of IHC Ki67 as a prognostic factor for breast cancer subgroups.Patients and MethodsWe retrospectively identified patients in the Tokai University breast cancer database for whom IHC Ki67 data were available between January 1, 2000 and December 31, 2010. Survival curves were calculated using the Kaplan-Meier method and compared using the log-rank test.ResultsOf the 1331 primary breast cancer patients included in the study, In patients with estrogen receptor (ER)-positive and HER2-negative tumors (n = 971), high and intermediate Ki67 scores were associated with poorer relapse-free survival than low Ki67 scores (P < .001 and P = .002, respectively). Furthermore, in the multivariate analyses of this subgroup, progression-free survival (PFS) was significantly longer in patients with low Ki67 scores than in patients with high Ki67 scores (hazard ratio, 0.387; 95% confidence interval, 0.233-0.643; P < .001). In the multivariate analyses, the Ki67 score was not significantly associated with PFS in the ER-positive and HER2-positive, ER-negative and HER2-positive, or ER-negative and HER2-negative subgroups.ConclusionOur data demonstrated that low, intermediate, and high Ki67 scores have a prognostic value in breast cancer patients with ER-positive and HER2-negative tumors.     

Effect of tamoxifen on Ki67 labelling index in human breast tumours and its relationship to oestrogen and progesterone receptor status.

This study aimed to investigate the effect of tamoxifen on breast tumour levels of oestrogen and progesterone receptor (ER and PR) and proliferation as defined by the Ki67 antibody. A group of primary breast cancer patients was randomised to receive either tamoxifen (n = 59) or placebo (n = 44) treatment in the interval between clinic and surgery (median 21 days). Frozen sections of breast tumour biopsies obtained before and after treatment were stained immunocytochemically to obtain the percentage of nuclei containing ER and PR, and a Ki67 labelling index (LI). Tamoxifen-treated patients had a median Ki67 LI of 5.6% in the first biopsy falling to 3.0% in the second biopsy (P < 0.001 by Wilcoxon''s matched pairs test), whereas placebo-treated patients had a median Ki67 LI of 5.4% in the first biopsy and 5.75% in the second (no significant difference). No significant differences were observed when the median %ER or %PR staining before and after treatment were compared. The Ki67 LI tended to increase with increasing histological grade and was greater in tumours that were ER - ve compared to those that were ER + ve (> 5% nuclei stained), median 7.8% and 4.3% respectively (P = 0.011 by Mann-Whitney U-test). However, the decline in tumour Ki67 LI following anti-oestrogen treatment failed to correlate with ER and PR status or to predict recurrence over a short follow-up period. To our knowledge, this is the first time that tamoxifen treatment has been shown to reduce the Ki67 LI in human breast tumours in vivo. These data indicate that staining with the Ki67 antibody may be useful in monitoring response to anti-oestrogen therapy.     

A novel molecular grading model: combination of Ki67 and VEGF in predicting tumor recurrence and progression in non-invasive urothelial bladder cancer

Purpose: To assess efficacy of Ki67 combined with VEGF as a molecular grading model to predict outcomeswith non-muscle invasive bladder cancer (NMIBC). Materials: 72 NMIBC patients who underwent transurethralresection (TUR) followed by routine intravesical instillations were retrospectively analyzed in this study.Univariate and multivariate analyses were performed to confirm the prognostic values of the Ki67 labeling index(LI) and VEGF scoring for tumor recurrence and progression. Results: The novel molecular grading modelfor NMIBC contained three molecular grades including mG1 (Ki67 LI≤25%, VEGF scoring≤8), mG2 (Ki67LI>25%, VEGF scoring ≤ 8; or Ki67 LI ≤ 25%, VEGF scoring > 8), and mG3 (Ki67 LI > 25%, VEGF scoring> 8), which can indicate favorable, intermediate and poor prognosis, respectively. Conclusions: The describednovel molecular grading model utilizing Ki67 LI and VEGF scoring is helpful to effectively and accuratelypredict outcomes and optimize personal therapy.     

Assessment of Ki67 in breast cancer: recommendations from the International Ki67 in Breast Cancer working group

Uncontrolled proliferation is a hallmark of cancer. In breast cancer, immunohistochemical assessment of the proportion of cells staining for the nuclear antigen Ki67 has become the most widely used method for comparing proliferation between tumor samples. Potential uses include prognosis, prediction of relative responsiveness or resistance to chemotherapy or endocrine therapy, estimation of residual risk in patients on standard therapy and as a dynamic biomarker of treatment efficacy in samples taken before, during, and after neoadjuvant therapy, particularly neoadjuvant endocrine therapy. Increasingly, Ki67 is measured in these scenarios for clinical research, including as a primary efficacy endpoint for clinical trials, and sometimes for clinical management. At present, the enormous variation in analytical practice markedly limits the value of Ki67 in each of these contexts. On March 12, 2010, an international panel of investigators with substantial expertise in the assessment of Ki67 and in the development of biomarker guidelines was convened in London by the co-chairs of the Breast International Group and North American Breast Cancer Group Biomarker Working Party to consider evidence for potential applications. Comprehensive recommendations on preanalytical and analytical assessment, and interpretation and scoring of Ki67 were formulated based on current evidence. These recommendations are geared toward achieving a harmonized methodology, create greater between-laboratory and between-study comparability, and allow earlier valid applications of this marker in clinical practice.     

Ki67 expression in invasive breast cancer: the use of tissue microarrays compared with whole tissue sections

Background

Although the prognostic value of Ki67 in breast cancer is well documented, using optimal cut-points for patient stratification, reproducibility of the scoring and interpretation of the results remains a matter of debate particularly when using tissue microarrays (TMAs). This study aims to assess Ki67 expression assessed on TMAs and their matched whole tissue sections (WTS). Moreover, whether the cut-off used for WTS is reproducible on TMA in BC molecular classes and the association between Ki67 expression cut-off, assessed on TMAs and WTS, and clinicopathological parameters and patient outcome were tested.

Method

A large series (n = 707) of primary invasive breast tumours were immunostained for Ki67 using both TMA and WTS and assessed as percentage staining and correlated with each other, clinicopathological parameters and patient outcome. In addition, MKI67 mRNA expression was correlated with Ki67 protein levels on WTS and TMAs in a subset of cases included in the METABRIC study.

Results

There was moderate concordance in Ki67 expression between WTS and TMA when analysed as a continuous variable (Intraclass correlation coefficient = 0.61) and low concordance when dichotomised (kappa value = 0.3). TMA showed low levels of Ki67 with mean percentage of expression of 35 and 22% on WTS and TMA, respectively. MKI67 mRNA expression was significantly correlated with protein expression determined on WTS (Spearman Correlation, r = 0.52) and to a lesser extent on TMA (r = 0.34) (p < 0.001). Regarding prediction of patient outcome, statistically significant differences were detected upon stratification of patients with tumours expressing Ki67 at 10, 15, 20, 25 or 30% in TMA. Using TMA, ≥20% Ki67 provided the best prognostic cut-off particularly in triple-negative and HER2-positive classes.

Conclusion

Ki67 expression in breast cancer can be evaluated using TMA although different cut-points are required to emulate results from WTS. A cut-off of ≥20% for Ki67 expression in BC provides the best prognostic correlations when TMAs are used.

     

A methodology to ensure and improve accuracy of Ki67 labelling index estimation by automated digital image analysis in breast cancer tissue

Introduction

Immunohistochemical Ki67 labelling index (Ki67 LI) reflects proliferative activity and is a potential prognostic/predictive marker of breast cancer. However, its clinical utility is hindered by the lack of standardized measurement methodologies. Besides tissue heterogeneity aspects, the key element of methodology remains accurate estimation of Ki67-stained/counterstained tumour cell profiles. We aimed to develop a methodology to ensure and improve accuracy of the digital image analysis (DIA) approach.

Methods

Tissue microarrays (one 1-mm spot per patient, n = 164) from invasive ductal breast carcinoma were stained for Ki67 and scanned. Criterion standard (Ki67-Count) was obtained by counting positive and negative tumour cell profiles using a stereology grid overlaid on a spot image. DIA was performed with Aperio Genie/Nuclear algorithms. A bias was estimated by ANOVA, correlation and regression analyses. Calibration steps of the DIA by adjusting the algorithm settings were performed: first, by subjective DIA quality assessment (DIA-1), and second, to compensate the bias established (DIA-2). Visual estimate (Ki67-VE) on the same images was performed by five pathologists independently.

Results

ANOVA revealed significant underestimation bias (P < 0.05) for DIA-0, DIA-1 and two pathologists’ VE, while DIA-2, VE-median and three other VEs were within the same range. Regression analyses revealed best accuracy for the DIA-2 (R-square = 0.90) exceeding that of VE-median, individual VEs and other DIA settings. Bidirectional bias for the DIA-2 with overestimation at low, and underestimation at high ends of the scale was detected. Measurement error correction by inverse regression was applied to improve DIA-2-based prediction of the Ki67-Count, in particular for the clinically relevant interval of Ki67-Count < 40%. Potential clinical impact of the prediction was tested by dichotomising the cases at the cut-off values of 10, 15, and 20%. Misclassification rate of 5-7% was achieved, compared to that of 11-18% for the VE-median-based prediction.

Conclusions

Our experiments provide methodology to achieve accurate Ki67-LI estimation by DIA, based on proper validation, calibration, and measurement error correction procedures, guided by quantified bias from reference values obtained by stereology grid count. This basic validation step is an important prerequisite for high-throughput automated DIA applications to investigate tissue heterogeneity and clinical utility aspects of Ki67 and other immunohistochemistry (IHC) biomarkers.     

Immunocytochemical results for HER2 and Ki67 in breast cancer touch-smear cell specimens are reliable

Background

Re-evaluation of the subtype of recurrent breast cancer is necessary for deciding the treatment approach, but it is often not performed due to the difficulty of obtaining tissue specimens from a recurrent lesion, etc. However, when a recurrent lesion is close to the body surface, fine-needle aspiration cells (FNA cells) can be easily obtained, and immunocytochemical (ICC) analysis of hormone receptors expression in FNA cells is said to be highly reliable. However, there is no consensus regarding ICC analysis of human epidermal growth factor receptor type 2 (HER2) expression and the Ki67 index using FNA cells.

Methods

Touch-smear cells (TSC) were prepared from resected specimens from 36 patients with primary invasive ductal carcinoma of the breast. The TSC were fixed in 95 % ethanol and subjected to ICC analysis for HER2 using HercepTest? (Dako) and Ki67 using MIB-1? (Dako). HER2 expression and the Ki67 index for the TSC were compared with the results of immunohistochemical analysis of histological section (HS). Statistical analyses used the kappa test and Pearson’s correlation coefficients.

Results

HER2 and Ki67 were analyzed in TSC from 36 and 28 patients, respectively. The HER2 expression scores in the TSC and HS groups showed good agreement (kappa value =0.640) and significant correlation (correlation coefficient =0.860, p < 0.001). The Ki67 indexes in the TSC and HS groups also showed significant correlation (correlation coefficient =0.861, p < 0.001).

Conclusions

The reliability of ICC analysis of HER2 expression and the Ki67 index using TSC were recognized.

     

Immunohistochemical analysis revealed CD34 and Ki67 protein expression as significant prognostic factors in colorectal cancer

CD34, cytokeratin (CK) 19, cytokeratin (CK) 20, and Ki67 have been demonstrated to be involved in tumor invasion and angiogenesis. The aim of this study was to analyze the clinicopathological significance of CD34, CK19, CK20, and Ki67 expressions in colorectal cancer (CRC) and to evaluate their involvement in the progression of CRC. CD34, CK19, CK20, and Ki67 expressions were assessed in paraffin-embedded specimens collected from 152 cases of CRC and 30 paired normal colorectal tissues by immunohistochemistry. The relationships between CD34, CK19, CK20, and Ki67 expressions and CRC were evaluated. The association of CD34 and Ki67 protein expressions with the clinicopathological characteristics and the prognosis of CRC were subsequently assessed. CD34, CK19, CK20, and Ki67 expressed highly in CRC tissues relative to normal colorectal tissues. Using immunostaining scoring, a significant correlation of CD34 and Ki67 with the UICC staging and histo-differentiation of CRC was found (P < 0.05), but no such correlation of CK19 and CK20 with the UICC staging and histo-differentiation (P > 0.05). Meanwhile, no relationship of CD34, CK19, CK20, and Ki67 with the location of CRC was found (P > 0.05). Patients with high expressions of CD34 and Ki67 had the lowest survival (P < 0.05). The results suggest that concurrent expression of CD34 and Ki67 may be an important characteristic of CRC which may help in the prediction of CRC progression.     

The Use of Digital Images Improves Reproducibility of the Ki-67 Labeling Index as a Proliferation Marker in Breast Cancer

The proportion of Ki-67 immunostained cells (Ki-67 labeling index, LI) is one of the most commonly used histology methods for estimating proliferation of breast carcinomas. Although the Ki-67 LI is used in treatment decision making, its reproducibility shows variation in different studies, and is generally less then optimal. The aim of the present study was to investigate how the use of a standardized, partially digitalized counting method could affect reproducibility of determining the Ki-67 LI. Thirty breast cancer core-biopsy samples were stained with B-56, SP-6 and MIB-1 monoclonal Ki-67 antibodies. Each sample was represented by a single digital photograph taken with a x20 objective. Four investigators determined the Ki-67 LI on these digital images by estimation, then by counting with the help of a grid overlaid on the same images. Altogether 720 evaluations were made by 4 independent pathologists. Good to excellent correlation was found between estimations and calculations of each observer. Kappa values >0.6 suggest substantial inter-observer agreement when classifying the cases into a 15 % and 30 % cut-off determined three-tiered or a 4-quarter-based four-tiered categorization, which is better than the fair reproducibility gained on the real slides in a previous study. The results also suggest that the type of the antibody may also impact on the consistency of both estimating and calculating the Ki-67 LIs. The results indicate that counting on digital images may significantly improve reproducibility of determining the KI-67 LI. Interestingly, estimation on the same images is not worse, but is obviously faster and more convenient.     

p53突变型乳腺癌中Ki67表达水平的临床意义

目的：探讨乳腺癌组织中p53的突变情况及Ki67的表达水平,明确p53与Ki67联合作用在乳腺癌临床病理因素上的体现。方法：应用免疫组化SP法检测165例乳腺癌组织中p53、Ki67的表达,分析其与临床病理因素之间的关系。结果：p53的突变率为55.8%（92/165）,Ki67的阳性表达率为69.1% （114/165）。p53的突变情况与患者年龄、肿块大小、淋巴结转移、TNM分期、ER和PR的表达水平无关,但与HER-2的表达水平呈正相关。在总人群中Ki67的表达水平与肿块大小和淋巴结转移无关。亚组分析显示在p53突变的患者中,Ki67的表达水平与肿块的大小呈正相关（r=0.311,P=0.003）,与淋巴结转移呈正相关（r=0.342,P=0.001）。结论：在p53突变型乳腺癌中Ki67的表达与T分期及N分期均呈正相关,在p53突变人群中Ki67对乳腺癌的生物学行为和患者的预后可能有更高的预测价值,二者联合检测与解读可能更有助于判断乳腺癌患者的预后。     

膜联蛋白A1和Ki67抗原在胰腺癌组织中的表达及其相互关系

[目的]探讨膜联蛋白A1（annexinA1,ANXA1）在胰腺癌中表达及其与细胞核相关抗原Ki67的相关性。[方法]构建胰腺癌组织芯片,在连续的芯片切片上使用免疫组化法检测ANXA1和Ki67蛋白表达情况,分析两者之间表达的相关性。[结果]胰腺癌组织芯片免疫组化结果显示,ANXA1在胰腺癌中表达的阳性率为71.4%（30/42）,明显高于正常胰腺组织中表达的阳性率18.4%（7/38）（P〈0.01）。Ki67在胰腺癌中表达的阳性率为69.5%（27/41）,也明显高于正常胰腺组织中表达的阳性率23.7%（9/38）（P〈0.01）。在胰腺癌中ANXA1与Ki67的表达存在显著的相关性（P〈0.01）。[结论]ANXA1蛋白在胰腺癌中的表达明显升高,与Ki67的表达有着显著的相关性。     

我国北方汉族女性乳腺癌中PELP1／MNAR表达特征及其与Ki-67标记指数相关性研究

目的观察我国北方汉族女性乳腺癌患者肿瘤组织中PELP1／MNAR表达特征及其与临床病理参数及Ki-67表达的相关性。方法采用免疫组化法检测98例北方汉族女性乳腺癌患者及22例乳腺良性纤维腺瘤患者肿瘤组织中PELP1／MNAR、Ki-67表达水平,比较PELP1／MNAR在乳腺良恶性肿瘤中的表达差别,就乳腺癌组织中PELP1／MNAR表达水平与临床参数及Ki-67表达水平进行相关性分析。结果乳腺癌组织中PELP1／MNAR表达阳性率显著高于良性乳腺纤维腺瘤组织（100％VS72．7％,P〈0．01）;乳腺癌组织中PELP1／MNAR表达强度与患者年龄、是否绝经、肿瘤病理分型未见相关性（P〉0．05）,与临床等级呈显著正相关（r=0．442,P〈0．01）;有淋巴结转移组PELP1／MNAR表达强度显著高于无淋巴结转移组（56．35V843．19,P=0．015）;PELP1／MNAR与Ki-67表达水平呈显著正相关（r=0．247,P=0．014）。结论PELP1／MNAR高表达是我国北方汉族女性原发性乳腺癌的一个特征并且可能成为判断乳腺癌预后的一个重要病理学指标。     

Ki67在三阴性乳腺癌中的表达及与C-erbB-2的关系

目的:对比研究Ki67基因在三阴性及非三阴性乳腺癌中的表达,并探讨Ki67与C-erbB-2基因表达间的相关性。方法:免疫组织化学法检测320例乳腺癌标本(273例为非三阴性乳腺癌,47例为三阴性乳腺癌)中Ki67及C-erbB-2的表达。结果:较之于非三阴性乳腺癌,三阴性乳腺癌中Ki67为过表达(P<0.01)。同时Ki67与C-erbB-2的表达强度间呈正相关(P<0.01)。结论:Ki67在三阴性乳腺癌中表达升高。     

Ki67 measured in metastatic tissue and prognosis in patients with advanced breast cancer

The purpose of this study is to determine the prognostic role of Ki67 evaluated in relapse biopsies from patients with metastatic breast cancer (MBC). Two hundred and ten patients diagnosed with MBC in Stockholm, Sweden between 1998 and 2009 and with Ki67 assessed at time of first systemic relapse (mKi67) were retrospectively identified and divided into two groups according to mKi67 fraction (low ≤20 %, high >20 %). Post-relapse survival was compared between the groups using Kaplan–Meier and Cox regression methods. Death rate as function of continuous mKi67 was also evaluated. Furthermore, the prognostic role of intra-individual change in Ki67 between primary tumor and matched metastasis was explored by Kaplan–Meier plots. One hundred and twenty-five patients had low and 85 had high mKi67. Median survival was 25 and 17 months in low- and high-mKi67 group, respectively [hazard ratio (HR) 0.69, 95 % confidence intervals (CI) 0.51–0.92, P = 0.01]. In a multivariate model adjusted for prognostic confounders, low-mKi67 showed a non-significant trend toward better survival (HR 0.85, 95 %CI 0.62–1.16, P = 0.30). Nevertheless, mKi67 independently correlated with survival when compared with primary tumor proliferation (HR 0.56, 95 %CI 0.38–0.81, P = 0.002). The 2-year death rate steeply increased as mKi67 increased. Moreover, the change from high in primary tumor to low in metastasis significantly correlated with longer survival when compared with stable Ki67 levels (HR 0.48, 95 %CI 0.31–0.76, P = 0.002). In this cohort of MBC patients, mKi67 inversely but not independently correlated with survival. However, a significant association between mKi67 and survival was shown regardless of primary tumor proliferation.     

Ki67 immunoreactivity in breast carcinoma: relationships to prognostic variables and short term survival.

Immunoreactivity of the monoclonal antibody Ki67, which recognizes an antigen expressed in cells active in the cell cycle, has been investigated by immunocytochemistry in a series of 67 primary breast cancers. The percentage of tumour cell nuclei stained by Ki67 (labelling index) was related to tumour histological grade, mitotic frequency, oestrogen receptor status and tumour type. No correlation was found with patient age, tumour size or lymph node stage. A high Ki67 labelling index was significantly associated with diminished patient survival and disease-free interval, which demonstrates an important role for this monoclonal antibody as a prognostic marker in breast cancer.     

Immunohistochemical Ki67 labeling index has similar proliferation predictive power to various gene signatures in breast cancer

The objective of this study was to examine the association between the immunohistochemical Ki67 labeling index (IHC Ki67), Ki67 mRNA expression level, and first-generation gene signatures in a cohort of breast cancer patients. We assessed associations between IHC Ki67 and first-generation gene signatures in a panel of 39 tumor samples, using an oligonucleotide microarray. Gene expression analyses included Ki67 alone (MKi67), 21-gene signature, mitosis kinome score signature, and genomic grade index. Correlation coefficients were calculated by Spearman's rank correlation test. In all cases, IHC Ki67, MKi67, and three genetic markers were highly correlated (ρ, 0.71-0.97). Estrogen receptor (ER)-positive cases showed strong correlations between IHC Ki67 and other signatures (ρ, 0.79-0.83). The ER-negative cases showed slightly lower correlations (ρ, 0.58-0.73). In ER-positive cases, the low IHC Ki67 group showed significantly longer relapse-free survival than the high IHC Ki67 group (P = 0.007). This difference was confirmed by multivariate analysis. Our data indicate that IHC Ki67 shows similar predictive power for proliferation in ER-positive cancers as genomic markers. Further study of IHC Ki67 is needed to define prognostic factors and predictive factors for chemotherapy using central laboratory assessment.