Association between Ki-67 expression and clinicopathological features in prognosis of breast cancer: A retrospective cohort study
Hosein Kamranzadeh1, Reza Manouchehri Ardekani1, Amir Kasaeian1, Sanambar Sadighi2, Somaye Maghsudi1, Issa Jahanzad3, Nasrollah Maleki1
1 Hematology, Oncology and Stem Cell Transplantation Research Center, Tehran University of Medical Sciences, Tehran, Iran
2 Department of Medical Oncology, Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Sciences, Tehran, Iran
3 Department of Pathology, Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Sciences, Tehran, Iran
|Date of Submission||11-Aug-2018|
|Date of Decision||13-Nov-2018|
|Date of Acceptance||30-Jan-2019|
|Date of Web Publication||26-Apr-2019|
Dr. Reza Manouchehri Ardekani
Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Kargar Shomali Street, Tehran University of Medical Sciences, Tehran
Source of Support: None, Conflict of Interest: None
Background: Breast cancer is the most common diagnosed female cancer. Breast cancer is also the leading cause of cancer death in females accounting for 13.7% of female cancer-related mortality globally. Variable known prognostic factors such as histological tumor type, tumor size, nodal status, grade, age, and estrogen receptor (ER) status and the proliferation marker – Ki-67 influence the type of treatment decision. The purpose of this present study is to investigate the association between Ki-67 expression with several clinicopathological variables and patients' outcome. Materials and Methods: This is a retrospective cohort study from September 2008 to March 2017; 165 newly diagnosed breast cancer patients were enrolled in the study. Ki67 levels were measured using immunohistochemistry and compared with clinicopathological variables. The relation of Ki67 expression with disease-free survival (DFS) and overall survival (OS) was also analyzed. Results: The result of this study revealed that age, tumor size, menopausal status, and human epidermal growth factor receptor 2 (HER2) status had no effect on the patients' outcome. Patients with ER-positive, progesterone receptor (PR)-positive, and HER2-negative tumors expressed a higher rate of Ki-67 (>10%) than patients with ER-negative, PR-negative, and HER2-positive tumors, respectively. However, we found that Ki-67 levels were not significantly increased statistically with ER, PR, and HER2 statuses. There was a statistically significant correlation between Ki-67 expression and with higher stages of the disease. Multivariate analysis showed that Ki-67 expression could not to be an independent prognostic factor for 5-year OS and DFS. Furthermore, p53 status was only prognostic factor for 5-year OS whereas higher stages of disease and p53 status were prognostic factors for 5-year DFS. Conclusion: Ki67 could not be an independent variable for prediction of breast cancer outcome.
Keywords: Breast neoplasms, immunohistochemistry, Ki-67 antigen, prognosis, survival
|How to cite this article:|
Kamranzadeh H, Ardekani RM, Kasaeian A, Sadighi S, Maghsudi S, Jahanzad I, Maleki N. Association between Ki-67 expression and clinicopathological features in prognosis of breast cancer: A retrospective cohort study. J Res Med Sci 2019;24:30
|How to cite this URL:|
Kamranzadeh H, Ardekani RM, Kasaeian A, Sadighi S, Maghsudi S, Jahanzad I, Maleki N. Association between Ki-67 expression and clinicopathological features in prognosis of breast cancer: A retrospective cohort study. J Res Med Sci [serial online] 2019 [cited 2020 Apr 8];24:30. Available from: http://www.jmsjournal.net/text.asp?2019/24/1/30/257247
| Introduction|| |
Breast cancer is the most frequently diagnosed cancer worldwide. It is by far the most frequent cancer among women, with an estimated 1.67 million new cancer cases diagnosed in 2012 (25% of all cancers). It is estimated that 268,670 new cases of breast cancer will be diagnosed, and 41,400 deaths will be attributed to this disease in the United States in 2018. According to GLOBOCAN 2012, breast cancer ranks as the fifth cause of death from cancer overall (522,000 deaths). Incidence rates vary nearly four-fold across the world regions, with rates ranging from 27/100,000 in Middle Africa and Eastern Asia to 92 in Northern America. The slight increase in breast cancer incidence from 2005 to 2014 was driven by increases of 0.3% per year among Hispanic women, 0.4% per year among non-Hispanic black women, and 1.7% per year among Asian/Pacific Islander women. The incidence of breast cancer is rising in Iranian women. Age-Standardized Incidence Rate increased from 15.96/100,000 in 2003 to 33.21/100,000 in 2008.
The development of new technologies and in particular, the use of complementary DNA microarrays will allow us now the simultaneous analysis of thousands of genes and the establishment of new, more refined breast cancer subtypes. In biological molecular research, especially for breast cancer, the analysis of combining biological pathway information with gene expression data may play an important role in regulating processes involved in this disease., For many years, tumor size, axillary lymph node status, histological characteristics of the tumor (especially histological grade of malignancy and invasion of lymphatic vessels), estrogen receptor (ER) and progesterone receptor (PR) status, human epidermal growth factor receptor 2 (HER2) expression, patient's age, and performance status were used to evaluate the prognosis and to determine the appropriate treatment strategy for breast cancer patients. Recognizing of tumor proliferation is one of the important prognostic factors that determines the adjuvant treatment decision in breast cancer. Over the past few decades, proliferation markers have been evaluated as prognostic factors in breast cancer.
Ki-67 labeling index (LI) and mitotic index (MI) are both proliferative indices, but their relationship is poorly defined. The Ki-67 antigen is expressed in the cell cycle phases G1, S, G2, and M, but not in G0. The level of expression of the Ki-67 protein varies during the cell cycle. Rates are low in G1 and early S phase and increase to a maximum at the time of mitosis. The most prevalent analysis method of Ki-67 antigen is the immunohistochemical evaluation. The rate of Ki-67 is most often measured on histological sections and is defined as the percentage of stained invasive carcinoma cells. The percentage of tumor cells expressing Ki-67 reflects the percentage of cells in the mitotic cycle within the tumor.
Data on the prognostic value of Ki-67 are limited in breast cancer. Unfortunately, there is no consensus about the importance of this proliferative marker. Some researchers support the prognostic value of Ki67 in breast cancer, while others have not found the same.,
The aim of the present study was to investigate the association between Ki-67 expression with several clinicopathological variables and to assess the outcome of patients with breast cancer.
| Materials and Methods|| |
Design and population
The study was approved by the Ethics Committee of the Tehran University of Medical Sciences. This was a retrospective cohort study. Newly diagnosed patients with breast cancer in the oncology outpatient clinic of Shariati Hospital in Tehran, Iran, between September 2008 and March 2017 were recruited for the study individuals. A total of 186 patients with breast cancer were included in this study. Exclusion criteria included metastatic disease, male gender, and those patients with incomplete data. Metastasis was detected in 21 patients, and Ki-64 data were not available in 58 cases. Therefore, inclusion criteria were met in 107 participants.
Tumor staging was performed according to tumor-node-metastasis (TNM) classification criteria. The clinicopathological factors were age, menstrual status, surgery type, lymph node involvement, tumor size, disease stage, chemotherapy, radiation therapy, and immunohistochemistry (IHC) results of ER, PR, HER2, and Ki67 status. Ki67 levels were compared with clinicopathological features. The association between Ki67 expression and disease-free survival (DFS) and overall survival (OS) was analyzed. DFS was the period after curative treatment when no disease can be detected, and OS was calculated from the time of initial diagnosis to the time of death.
The samples were previously immunohistochemically stained to the manufacturer's guidelines (Ki-67 antibody; MIB-1 DAKO, dilution 1:200) and reviewed separately by second pathologists.
For IHC of Ki67, many cutoff values have been used although staining levels of 10%–20% are the most commonly used for the classification of invasive breast cancers. Some researchers have described that the choice of the optimal cutoff point for IHC may depend on the clinical purpose: if Ki-67 is used to exclude patients with slowly proliferating tumors from chemotherapy protocols, a cutoff point of 10% will help avoid overtreatment. Conversely, if Ki-67 is used to identify patients sensitive to chemotherapy protocols, it is preferable to set the cutoff at 25%. In this study, we preferred to use a cutoff at 10% for Ki-67 as has been found in other studies.,, Specimens with <10% of stained tumor cells were defined as negative, and specimens with 10% or more of stained tumor cells were defined as a positive Ki67 expression. The patients were followed up until death or the end of the observation period (March 2017). The median follow-up duration was 49 months (range, 3–113 months).
The statistical analysis of the data was performed using the SPSS software for Windows, version 22 (SPSS Inc., Chicago, IL, USA). P < 0.05 was considered statistically significant. The association between clinicopathologic factors and expression of Ki-67 was determined using Chi-square/Fisher's exact tests. The results were expressed as means ± standard deviations. For assessment of prognostic factors, univariate and multivariate analysis were performed using the Cox-proportional hazard model. The variables with P < 0.2 in the univariate analysis were analyzed with multivariate Cox proportional hazard model. Kaplan–Meier curves were derived to determine OS and DFS and were compared by means of the log-rank test. Median follow-up time was established with the reverse Kaplan–Meier method.
| Results|| |
Characteristics of patients
A total of 165 newly diagnosed breast cancer patients were enrolled in this study. The characteristics of these patients are shown in [Table 1]. The average age of patients was 47.4 years (ranging from 24 to 76). It was found that most of the patients had node-negative disease (39.5%). According to TNM classification, 56.4% of the patients had T2 and 53.9% of the patients had Stage II disease. Based on histological grading results, we categorized patients into 2 groups: Group 1 (includes Grades I and II; 84.8% of the patients) and Group 2 (includes Grade III; 15.2% of the patients). Two patients (1.2%) only needed a core needle biopsy, and the rest of them (98.8%) underwent surgery (breast conservation therapy and modified radical mastectomy).
ER positivity was present in 107 patients (64.8%), and PR positivity in 98 patients (59.4%). Forty patients (24.2%) had Her2 positive disease. Ki67 was positive (>10% immunoreactive cells) in 74 patients (69.16%). The median follow-up was 5 years (61 months); nineteen patients died during this period of the time. At the end of follow-up, we used Kaplan–Meier method to estimate OS. The estimated 3- and 5-year OS were 93.31% (95% confidence interval [CI] 86.48%–96.76%) and 86.62% (95% CI 78.61%–94.63%), respectively. In addition, the estimated 3- and 5-year DFS were 87.67% (95% CI 79.71%–92.65%) and 79% (95% CI 68.19%–86.49%), respectively. Adjusted 5-year survival for disease stage was 93.75% for Stage I, 92.27% for Stage II, and 47.59% for Stage III.
Results of prognostic analysis are shown in [Table 2]. We observed no statistically significant difference (P > 0.05) in terms of OS and DFS for age (P = 0.32), tumor size (P = 0.62), HER2 status (P = 0.22), menopausal status (P = 0.78), and tumor grade (P = 0.05). On the other hand, the prognostic variable with statistically significant differences for OS were ER status (P = 0.01), PR status (P = 0.03), and disease stages (P = 0.02). There was a significant difference between lymph node stages (P = 0.001) and OS in breast cancer patients, which indicated that the presence of lymph node involvement suggests a poor prognosis. However, no significant differences were observed between the positive and negative groups of Ki67 for OS and DFS. Five-year OS for Ki67-negative breast cancer was 74.22% (95% CI: 30.85%–92.72%) and 84.68% (95% CI: 71.49%–92.10%) for Ki67-positive cancers [Figure 1] and [Figure 2]. The difference between variables based on OS and DFS is summarized in [Table 2]. There was no significant relationship between menopausal status and Ki67. Forty-seven premenopausal patients (63.51%) and 27 menopausal patients (36.49%) had Ki67 more than 10% (P = 0.53).
Relationship between Ki-67 expression and the clinicopathological characteristics
The relationship between Ki-67 expression and the clinicopathological characteristics of breast cancer patients is summarized in [Table 3]. Patients with ER-positive and PR-positive tumors expressed a higher rate of Ki-67 (>10% immunoreactive cells) than patients with ER-negative and PR-negative tumors. However, we found that Ki67 level was not significantly increased in ER-positive and PR-positive patients (66.23% and 64.86%, respectively). Interestingly, patients with HER2-negative tumors expressed a significantly higher rate of Ki-67 (>10% immunoreactive cells) than patients with HER2-positive tumors (82.4% and 17.6%, respectively). Moreover, Ki67 level was not significantly increased in HER2-positive compared with HER2-negative patients (65% and 70.1%, respectively).
|Table 3: The relationship between Ki-67 expression and the clinicopathological characteristics of patients|
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According to the pathological stage, 7 patients with Stage I (9.46%), 41 patients with Stage II (55.41%) and 26 patients with Stage III (35.14%) had a positive ki67, and significant positive correlation was demonstrated between Ki-67 and the stage of the disease (P = 0.03). However, no significant association was found between the involvement of lymph nodes or the grade of the disease with Ki-67 expression (0.31% and 0.19%, respectively).
Prognostic variables for mortality were analyzed by using the multivariate Cox proportional hazards model, and variables with a P < 0.2 in univariate analysis were used in the stepwise multivariate Cox proportional hazards model. The result of this modeling revealed that age, tumor size, menopausal status, and HER2 status had no effect on the patient's outcome; so, we used the other variable for multivariable analysis, as shown in [Table 4].
|Table 4: Univariate and multivariate Cox proportional hazards model analysis|
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In addition, we use tumor grade, tumor stages, hormone receptor, and p53 status as multivariate, and results revealed that Ki67 could not to be an independent prognostic factor for OS (heart rate [HR] 0.55, 95% CI 0.13–2.33); P value (0.42) and DFS (HR 1.05, 95% CI 0.30–3.62); P value (0.92). Multivariate analysis showed that Ki-67 expression could not to be an independent prognostic factor for 5-year OS and DFS. Furthermore, p53 status was only prognostic factor for 5-year OS whereas higher stages of disease and p53 status were prognostic factors for 5-year DFS.
| Discussion|| |
Tumor markers are molecules that occur in cancer-related tissues and are useful for diagnosis, treatment, or clinical management, especially in patients with breast cancer. Ki67 is a marker of cell proliferation and has been used to stratify prognostic values in invasive breast cancer. This study was conducted to evaluate the prevalence of Ki67 as a proliferative index and to determine the prognostic and predictive value in patients with breast cancer. In addition, we tried to show the relationship between Ki67 and prognostic factors and the effect of Ki67 on the outcome of the disease. According to IHC results, 69.16% of patients had Ki67 >10%, which is considered a positive status. In line with our results, Shandiz et al. reported that 62.3% of patients were positive for Ki67 with a significant relation to lower age and P53 positivity.
Some researchers have found that Ki67 LI not correlate with tumor size, pathologic stage, expression of ER, PR, Her-2/neu, tumor histology, breast cancer subtypes, and age at diagnosis. Similarly, another study on 184 Iranian patients with breast cancer showed no correlation between ER and PR with p53 and Ki67. These findings are not consistent with the results of the present study. In our study, we failed to find a statistically significant relationship between the level of Ki67 and menopausal status (P = 0.53), hormone receptors (P = 0.29), as well as HER 2 status (P = 0.65).
In Finland, Pietiläinen et al. analyzed a series of 191 female breast carcinomas immunohistochemically for Ki-67 expression. In this study, Ki-67 expression was directly correlated with histological grade, the content of ER and PR, p53 accumulation, MI, S-phase fraction, and apoptotic index. However, no correlation was observed between the expression of Ki-67 and the status of lymph node, metastasis, and tumor size. In axillary lymph node-positive tumors, the expression of Ki-67 was not significantly associated with the recurrence-free survival. Multivariate survival analysis showed that tumor size, MI, and axillary lymph node status were independent prognostic factors in all cases whereas tumor size and Ki-67 expression were independent prognostic factors in axillary lymph node-negative cases. These researchers suggested that the expression of Ki-67 could be an important prognostic factor in breast cancer.
Our results revealed that Ki67 was associated with stage of breast cancer (P = 0.03), indicating that a high levels of Ki67 are found in more invasive tumors. In line with this result, results of a large population-based cohort of a cancer registry reported that Ki67 expression was associated with common histopathological parameters but was an additional independent prognostic parameter for DFS and OS in patients with breast cancer. In this study, the strongest correlation was found between grading and Ki67. In addition, they showed that higher tumor stages and node status were associated with higher Ki-67 quartiles, suggesting that the more aggressive tumor had a higher percentage of cells positively stained for Ki67. In another study, Abubakar et al. reviewed 8088 breast cancer patients from 10 study groups and showed that patients in the highest quartile of Ki67 (>12% positive Ki67 cells; that is close to our limit) had a worse 10-year breast cancer-specific survival than patients in the lower three quartiles. This relationship was statistically significant for ER-positive patients but not for ER-negative patients. Among the ER-positive cancers, Ki67 was accompanied by a worse prognosis in both node-negative and node-positive tumors. In 2011, Soliman and Yussif  performed a study to determine the clinical significance of Ki-67 index in different molecular subtypes of 107 patients with breast cancer. They concluded that patients with Ki67 <15% experience better OS than those with higher levels of Ki67. In addition, patients with Ki-67 higher than 15% were significantly correlated with adverse prognostic factors, high mitotic count, high tumor grade, ER−/PR−, higher incidence of metastasis, and recurrence than those with Ki-67 <15%.
Our study was unable to find out the effect of Ki67 in OS and DFS (P = 0.42 and P = 0.92, respectively). In addition, similarly to other literature, which indicates a significant impact of tumor grade, disease stage, and lymph node involvement in OS and DFS, the present study showed that the same variable was associated with a negative impact on OS and DFS. Unlike the studies previously mentioned, in the present study, we had not found any prognostic significance for ER and PR receptors regarding OS and DFS. In our study, the grade of tumor has not been statistically significant value for DFS and OS. These findings are inconsistent with the results of some studies.
The findings in this study are subject to several limitations. First, this study was a single center with a limited sample size, and these results may not be generalizable to other centers. Large-scale population studies are necessary to confirm these observations. Second, this study did not assess to precise evaluation of the relationship between Ki67 and the relapse risk.
| Conclusion|| |
According to the results of the present study, Ki67 could not be used as an independent prognostic factor for invasive breast cancers. It was also concluded that there is no significant relationship between Ki67 and some prognostic factors such as hormonal receptors and HER2. In addition, no significant difference was observed between Ki67 and 3- and 5-year DFS with 5-year OS.
Financial support and sponsorship
This study was financially supported by Tehran University of Medical Sciences.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Ferlay J, Soerjomataram I, Dikshit R, Eser S, Mathers C, Rebelo M, et al.
Cancer incidence and mortality worldwide: Sources, methods and major patterns in GLOBOCAN 2012. Int J Cancer 2015;136:E359-86.
Siegel RL, Miller KD, Jemal A. Cancer statistics, 2018. CA Cancer J Clin 2018;68:7-30.
Ferlay J, Soerjomataram I, Ervik M, Dikshit R, Eser S, Mathers C, et al
. GLOBOCAN 2012 V 1.0, Cancer Incidence and Mortality Worldwide: IARC Cancer Base No. 11. Lyon, France: International Agency for Research on Cancer; 2013. Available from: http://globocan.iarc.fr
. [Last accessed 2017 Aug 23].
DeSantis CE, Ma J, Goding Sauer A, Newman LA, Jemal A. Breast cancer statistics, 2017, racial disparity in mortality by state. CA Cancer J Clin 2017;67:439-48.
Rafiemanesh H, Salehiniya H, Lotfi Z. Breast cancer in Iranian woman: Incidence by age group, morphology and trends. Asian Pac J Cancer Prev 2016;17:1393-7.
Martín M. Molecular biology of breast cancer. Clin Transl Oncol 2006;8:7-14.
Moghaddam SE, Barzegar A, Nikbakhsh N. Study of the regulatory promoter polymorphism (-938C and >A) of B-cell lymphoma 2 gene in breast cancer patients of Mazandaran Province in Northern Iran. J Res Med Sci 2017;22:21.
] [Full text]
Mehrgou A, Akouchekian M. Therapeutic impacts of microRNAs in breast cancer by their roles in regulating processes involved in this disease. J Res Med Sci 2017;22:130.
] [Full text]
Adam Maciejczyk A. New prognostic factors in breast cancer. Adv Clin Exp Med 2013;22:5-15.
Harris L, Fritsche H, Mennel R, Norton L, Ravdin P, Taube S, et al.
American society of clinical oncology 2007 update of recommendations for the use of tumor markers in breast cancer. J Clin Oncol 2007;25:5287-312.
Rossi L, Laas E, Mallon P, Vincent-Salomon A, Guinebretiere JM, Lerebours F, et al.
Prognostic impact of discrepant ki67 and mitotic index on hormone receptor-positive, HER2-negative breast carcinoma. Br J Cancer 2015;113:996-1002.
Lopez F, Belloc F, Lacombe F, Dumain P, Reiffers J, Bernard P, et al.
Modalities of synthesis of ki67 antigen during the stimulation of lymphocytes. Cytometry 1991;12:42-9.
Clarke RB, Howell A, Potten CS, Anderson E. Dissociation between steroid receptor expression and cell proliferation in the human breast. Cancer Res 1997;57:4987-91.
Reyal F, Hajage D, Savignoni A, Feron JG, Bollet MA, Kirova Y, et al
. Long-term prognostic performance of Ki67 rate in early stage, pT1-pT2, pN0, invasive breast carcinoma. PLoS One. 2013;8:e55901.
de Azambuja E, Cardoso F, de Castro G Jr. Colozza M, Mano MS, Durbecq V, et al.
Ki-67 as prognostic marker in early breast cancer: A meta-analysis of published studies involving 12,155 patients. Br J Cancer 2007;96:1504-13.
Ono M, Tsuda H, Yunokawa M, Yonemori K, Shimizu C, Tamura K, et al.
Prognostic impact of Ki-67 labeling indices with 3 different cutoff values, histological grade, and nuclear grade in hormone-receptor-positive, HER2-negative, node-negative invasive breast cancers. Breast Cancer 2015;22:141-52.
Spyratos F, Ferrero-Poüs M, Trassard M, Hacène K, Phillips E, Tubiana-Hulin M, et al.
Correlation between MIB-1 and other proliferation markers: Clinical implications of the MIB-1 cutoff value. Cancer 2002;94:2151-9.
Bos R, van der Groep P, Greijer AE, Shvarts A, Meijer S, Pinedo HM, et al.
Levels of hypoxia-inducible factor-1alpha independently predict prognosis in patients with lymph node negative breast carcinoma. Cancer 2003;97:1573-81.
Bevilacqua P, Verderio P, Barbareschi M, Bonoldi E, Boracchi P, Palma PD, et al.
Lack of prognostic significance of the monoclonal antibody ki-S1, a novel marker of proliferative activity, in node-negative breast carcinoma. Breast Cancer Res Treat 1996;37:123-33.
Domagala W, Markiewski M, Harezga B, Dukowicz A, Osborn M. Prognostic significance of tumor cell proliferation rate as determined by the MIB-1 antibody in breast carcinoma: Its relationship with vimentin and p53 protein. Clin Cancer Res 1996;2:147-54.
Shandiz FH, Shabahang H, Afzaljavan F, Sharifi N, Tavasoli A, Afzalaghaee M, et al.
Ki67 frequency in breast cancers without axillary lymph node involvement and its relation with disease-free survival. Asian Pac J Cancer Prev 2016;17:1347-50.
Awadelkarim KD, Mariani-Costantini R, Osman I, Barberis MC. Ki-67 labeling index in primary invasive breast cancer from Sudanese patients: A pilot study. ISRN Pathol 2012;2012:232171.
Sheikhpour R, Poorhosseini F. Relation between estrogen and progesterone receptor status with p53, Ki67 and Her-2 markers in patients with breast cancer. Int J Bifurcat Chaos 2016;8:93-7.
Pietiläinen T, Lipponen P, Aaltomaa S, Eskelinen M, Kosma VM, Syrjänen K, et al.
The important prognostic value of ki-67 expression as determined by image analysis in breast cancer. J Cancer Res Clin Oncol 1996;122:687-92.
Inwald EC, Klinkhammer-Schalke M, Hofstädter F, Zeman F, Koller M, Gerstenhauer M, et al.
Ki-67 is a prognostic parameter in breast cancer patients: Results of a large population-based cohort of a cancer registry. Breast Cancer Res Treat 2013;139:539-52.
Abubakar M, Orr N, Daley F, Coulson P, Ali HR, Blows F, et al.
Prognostic value of automated KI67 scoring in breast cancer: A centralised evaluation of 8088 patients from 10 study groups. Breast Cancer Res 2016;18:104.
Soliman NA, Yussif SM. Ki-67 as a prognostic marker according to breast cancer molecular subtype. Cancer Biol Med 2016;13:496-504.
Cianfrocca M, Goldstein LJ. Prognostic and predictive factors in early-stage breast cancer. Oncologist 2004;9:606-16.
Elston CW, Ellis IO. Pathological prognostic factors in breast cancer. I. The value of histological grade in breast cancer: Experience from a large study with long-term follow-up. Histopathology 2002;41:154-61.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]