Prognostic value of Ki67 expression after short-term presurgical endocrine therapy for primary breast cancer

Phosphatidylinositol 3-kinase and antiestrogen resistance in breast cancer

Although antiestrogen therapies targeting estrogen receptor (ER) α signaling prevent disease recurrence in the majority of patients with hormone-dependent breast cancer, a significant fraction of patients exhibit de novo or acquired resistance. Currently, the only accepted mechanism linked with endocrine resistance is amplification or overexpression of the ERBB2 (human epidermal growth factor receptor 2 [HER2]) proto-oncogene. Experimental and clinical evidence suggests that hyperactivation of the phosphatidylinositol 3-kinase (PI3K) pathway, the most frequently mutated pathway in breast cancer, promotes antiestrogen resistance. PI3K is a major signaling hub downstream of HER2 and other receptor tyrosine kinases. PI3K activates several molecules involved in cell-cycle progression and survival, and in ER-positive breast cancer cells, it promotes estrogen-dependent and -independent ER transcriptional activity. Preclinical tumor models of antiestrogen-resistant breast cancer often remain sensitive to estrogens and PI3K inhibition, suggesting that simultaneous targeting of the PI3K and ER pathways may be most effective. Herein, we review alterations in the PI3K pathway associated with resistance to endocrine therapy, the state of clinical development of PI3K inhibitors, and strategies for the clinical investigation of such drugs in hormone receptor-positive breast cancer.

Predictive and prognostic molecular markers for cancer medicine

Over the last 10 years there has been an explosion of information about the molecular biology of cancer. A challenge in oncology is to translate this information into advances in patient care. While there are well-formed routes for translating new molecular information into drug therapy, the routes for translating new information into sensitive and specific diagnostic, prognostic and predictive tests are still being developed. Similarly, the science of using tumor molecular profiles to select clinical trial participants or to optimize therapy for individual patients is still in its infancy. This review will summarize the current technologies for predicting treatment response and prognosis in cancer medicine, and outline what the future may hold. It will also highlight the potential importance of methods that can integrate molecular, histopathological and clinical information into a synergistic understanding of tumor progression. While these possibilities are without doubt exciting, significant challenges remain if we are to implement them with a strong evidence base in a widely available and cost-effective manner.

Ki-67: level of evidence and methodological considerations for its role in the clinical management of breast cancer: analytical and critical review

Clinicians can use biomarkers to guide therapeutic decisions in estrogen receptor positive (ER+) breast cancer. One such biomarker is cellular proliferation as evaluated by Ki-67. This biomarker has been extensively studied and is easily assayed by histopathologists but it is not currently accepted as a standard. This review focuses on its prognostic and predictive value, and on methodological considerations for its measurement and the cut-points used for treatment decision. Data describing study design, patients’ characteristics, methods used and results were extracted from papers published between January 1990 and July 2010. In addition, the studies were assessed using the REMARK tool. Ki-67 is an independent prognostic factor for disease-free survival (HR 1.05–1.72) in multivariate analyses studies using samples from randomized clinical trials with secondary central analysis of the biomarker. The level of evidence (LOE) was judged to be I-B with the recently revised definition of Simon. However, standardization of the techniques and scoring methods are needed for the integration of this biomarker in everyday practice. Ki-67 was not found to be predictive for long-term follow-up after chemotherapy. Nevertheless, high KI-67 was found to be associated with immediate pathological complete response in the neoadjuvant setting, with an LOE of II-B. The REMARK score improved over time (with a range of 6–13/20 vs. 10–18/20, before and after 2005, respectively). KI-67 could be considered as a prognostic biomarker for therapeutic decision. It is assessed with a simple assay that could be standardized. However, international guidelines are needed for routine clinical use.

gef gene expression in MCF-7 breast cancer cells is associated with a better prognosis and induction of apoptosis by p53-mediated signaling pathway

Breast cancer research has developed rapidly in the past few decades, leading to longer survival times for patients and opening up the possibility of developing curative treatments for advanced breast cancer. Our increasing knowledge of the biological pathways associated with the progression and development of breast cancer, alongside the failure of conventional treatments, has prompted us to explore gene therapy as an alternative therapeutic strategy. We previously reported that gef gene from E. coli has shown considerable cytotoxic effects in breast cancer cells. However, its action mechanism has not been elucidated. Indirect immunofluorescence technique using flow cytometry and immunocytochemical analysis were used to detect breast cancer markers: estrogen (ER) and progesterone (PR) hormonal receptors, human epidermal growth factor receptor-2 proto-oncogene (c-erbB-2), ki-67 antigen and p53 protein. gef gene induces an increase in ER and PR expressions and a decrease in ki-67 and c-erbB-2 gene expressions, indicating a better prognosis and response to treatment and a longer disease-free interval and survival. It also increased p53 expression, suggesting that gef-induced apoptosis is regulated by a p53-mediated signaling pathway. These findings support the hypothesis that the gef gene offers a new approach to gene therapy in breast cancer.

Tailoring therapy for locally advanced breast cancer using molecular profiles: are we there yet?

The term 'locally advanced breast cancer' covers a range of clinical scenarios, and has the implications that surgical clearance and local control will be difficult or impossible, and long-term survival rates will be poor. Treatment selection is particularly important in this group of patients to try to obtain maximum control of disease, and potentially improve surgical options and cure rates. Currently, assessment of estrogen receptor, progesterone receptor and human epidermal receptor 2 status in tumour samples remains the gold standard for prediction of response to endocrine therapy, chemotherapy or targeted agents such as trastuzumab. Progress has been made in identifying markers that can help select treatments likely to be associated with response and avoid those associated with resistance. These potential markers include Ki67 proliferation rate, cytochrome P450 (CYP) 2D6 expression, BRCA1/2 gene status and others.

Adjuvant sequencing of tamoxifen and anastrozole is superior to tamoxifen alone in postmenopausal women with low proliferating breast cancer

PURPOSE

To assess the predictive value of Ki67 expression in postmenopausal hormone receptor-positive early-breast cancer patients, who were either treated with adjuvant tamoxifen (TAM) alone or with TAM followed by anastrozole (ANA).

EXPERIMENTAL DESIGN

Expression of Ki67 was determined centrally by immunohistochemistry on whole tissue sections of postmenopausal endocrine-responsive breast cancers from patients who had been enrolled in the prospectively randomized Austrian Breast and Colorectal Cancer Study Group Trial 8, and had received TAM for 5 years, or TAM for 2 years followed by ANA for 3 years. Ki67 expression was evaluated both as a continuous variable and dichotomized to low (≤10%) and high (>10%). Recurrence-free survival (RFS) and overall survival (OS) were analyzed using Cox models adjusted for clinical and pathologic parameters.

RESULTS

Patients with a high Ki67 expression (394/1,587; 23%) had a significantly shorter RFS (adjusted HR for recurrence = 1.90, 95% CI: 1.37-2.64, P = 0.0001) and OS (adjusted HR for death = 1.78, 95% CI: 1.18-2.70, P = 0.006). In women with breast tumors expressing medium or high ER levels (n = 1,438), the interaction between Ki67 and adjuvant endocrine treatment was significant for RFS (P = 0.03). TAM followed by ANA was superior to TAM alone in patients with low Ki67 (adjusted HR = 0.53, 95% CI: 0.34-0.83, P = 0.005) but not in high Ki67 disease (adjusted HR = 1.18, 95% CI: 0.66-1.89, P = 0.68).

CONCLUSIONS

Adjuvant sequencing of TAM and ANA is superior to TAM alone, particularly in postmenopausal women with medium or high ER expressing, low proliferating breast cancer.

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.

GSTP1 DNA methylation and expression status is indicative of 5-aza-2'-deoxycytidine efficacy in human prostate cancer cells

DNA methylation plays an important role in carcinogenesis and the reversibility of this epigenetic modification makes it a potential therapeutic target. To date, DNA methyltransferase inhibitors (DNMTi) have not demonstrated clinical efficacy in prostate cancer, with one of the major obstacles being the inability to monitor drug activity during the trial. Given the high frequency and specificity of GSTP1 DNA methylation in prostate cancer, we investigated whether GSTP1 is a useful marker of DNMTi treatment efficacy. LNCaP prostate cancer cells were treated with 5-aza-2′-deoxycytidine (5-aza-CdR) either with a single high dose (5–20 µM), every alternate day (0.1–10 µM) or daily (0.005–2.5 µM). A daily treatment regimen with 5-aza-CdR was optimal, with significant suppression of cell proliferation achieved with doses of 0.05 µM or greater (p<0.0001) and induction of cell death from 0.5 µM (p<0.0001). In contrast, treatment with a single high dose of 20 µM 5-aza-CdR inhibited cell proliferation but was not able to induce cell death. Demethylation of GSTP1 was observed with doses of 5-aza-CdR that induced significant suppression of cell proliferation (≥0.05 µM). Re-expression of the GSTP1 protein was observed only at doses of 5-aza-CdR (≥0.5 µM) associated with induction of cell death. Treatment of LNCaP cells with a more stable DNMTi, Zebularine required at least a 100-fold higher dose (≥50 µM) to inhibit proliferation and was less potent in inducing cell death, which corresponded to a lack of GSTP1 protein re-expression. We have shown that GSTP1 DNA methylation and protein expression status is correlated with DNMTi treatment response in prostate cancer cells. Since GSTP1 is methylated in nearly all prostate cancers, our results warrant its testing as a marker of epigenetic therapy response in future clinical trials. We conclude that the DNA methylation and protein expression status of GSTP1 are good indicators of DNMTi efficacy.

A kinome-wide screen identifies the insulin/IGF-I receptor pathway as a mechanism of escape from hormone dependence in breast cancer

Estrogen receptor α (ER)-positive breast cancers adapt to hormone deprivation and become resistant to antiestrogens. In this study, we sought to identify kinases essential for growth of ER(+) breast cancer cells resistant to long-term estrogen deprivation (LTED). A kinome-wide siRNA screen showed that the insulin receptor (InsR) is required for growth of MCF-7/LTED cells. Knockdown of InsR and/or insulin-like growth factor-I receptor (IGF-IR) inhibited growth of 3 of 4 LTED cell lines. Inhibition of InsR and IGF-IR with the dual tyrosine kinase inhibitor OSI-906 prevented the emergence of hormone-independent cells and tumors in vivo, inhibited parental and LTED cell growth and PI3K/AKT signaling, and suppressed growth of established MCF-7 xenografts in ovariectomized mice, whereas treatment with the neutralizing IGF-IR monoclonal antibody MAB391 was ineffective. Combined treatment with OSI-906 and the ER downregulator fulvestrant more effectively suppressed hormone-independent tumor growth than either drug alone. Finally, an insulin/IGF-I gene expression signature predicted recurrence-free survival in patients with ER(+) breast cancer treated with the antiestrogen tamoxifen. We conclude that therapeutic targeting of both InsR and IGF-IR should be more effective than targeting IGF-IR alone in abrogating resistance to endocrine therapy in breast cancer.

ERα-dependent E2F transcription can mediate resistance to estrogen deprivation in human breast cancer

Most estrogen receptor α (ER)-positive breast cancers initially respond to antiestrogens, but many eventually become estrogen-independent and recur. We identified an estrogen-independent role for ER and the CDK4/Rb/E2F transcriptional axis in the hormone-independent growth of breast cancer cells. ER downregulation with fulvestrant or small interfering RNA (siRNA) inhibited estrogen-independent growth. Chromatin immunoprecipitation identified ER genomic binding activity in estrogen-deprived cells and primary breast tumors treated with aromatase inhibitors. Gene expression profiling revealed an estrogen-independent, ER/E2F-directed transcriptional program. An E2F activation gene signature correlated with a lesser response to aromatase inhibitors in patients' tumors. siRNA screening showed that CDK4, an activator of E2F, is required for estrogen-independent cell growth. Long-term estrogen-deprived cells hyperactivate phosphatidylinositol 3-kinase (PI3K) independently of ER/E2F. Fulvestrant combined with the pan-PI3K inhibitor BKM120 induced regression of ER(+) xenografts. These data support further development of ER downregulators and CDK4 inhibitors, and their combination with PI3K inhibitors for treatment of antiestrogen-resistant breast cancers.

Individualization of treatment strategies

This section focuses on different aspects of the individualization of hormone treatment in breast cancer. This includes tumor-related biological factors such as expression of hormone receptors, HER-2, and Ki-67; host-related factors such as CYP2D6 or body mass index, and risk and/or development of specific toxicities and treatment adherence. The best predictor of response to hormonal interventions is the expression of hormone receptors, in particular, estrogen receptors. Treatment adherence and compliance are key factors and strategies aiming to identify and intervene when patients are at risk of abandoning treatment. Currently, routine assessment of CYP2D6 is not recommended to guide tamoxifen treatment. Likewise, there are no criteria regarding bone mass density, lipid profile, or arthralgias to recommend one class of agent versus another. Aromatase inhibitors should not be administered to patients who are pre- or perimenopausal.

Challenges translating breast cancer gene signatures into the clinic

The advent of microarray-based gene-expression profiling a decade ago raised high expectations for rapid advances in breast cancer classification, prognostication and prediction. Despite the development of molecular classifications, and prognostic and predictive gene-expression signatures, microarray-based studies have not yielded definitive answers to many of the questions that remain germane for the successful implementation of personalized medicine. There are a lack of robust signatures to predict benefit from specific therapeutic agents and it is still not possible to predict prognosis or chemotherapy treatment response in specific disease subsets accurately, such as triple-negative breast cancer. We discuss the hurdles in the development and validation of molecular classification systems, and prognostic and predictive signatures based on microarray gene-expression profiling. We suggest that similar challenges are likely to be encountered in translating next-generation sequencing data into clinically useful information. Finally we highlight strategies for the development of clinically useful molecular predictors in the future.

The ethical use of mandatory research biopsies

Increasingly, clinical trials incorporate translational research questions aimed at identifying biomarkers of response or resistance to agents under investigation. Biomarker assays can require tissue samples to be collected through a research biopsy before therapy, during treatment, or at the time of tumor progression. Such biopsy samples will generally not provide a direct benefit to the patient and, given the risks associated with any surgical procedure, ethical concerns have been raised when the participant's enrollment on a clinical trial depends on their consent to undergo a research biopsy. In this Perspectives article, we present the rationale for mandatory research biopsies and offer suggestions for standardization to ensure that high-quality, patient-centered, clinical trials continue to be designed with scientific and ethical rigor.

A phase II neoadjuvant trial of anastrozole, fulvestrant, and gefitinib in patients with newly diagnosed estrogen receptor positive breast cancer

Endocrine therapy in patients with breast cancer can be limited by the problem of resistance. Preclinical studies suggest that complete blockade of the estrogen receptor (ER) combined with inhibition of the epidermal growth factor receptor can overcome endocrine resistance. We tested this hypothesis in a phase II neoadjuvant trial of anastrozole and fulvestrant combined with gefitinib in postmenopausal women with newly diagnosed ER-positive breast cancer. After a baseline tumor core biopsy, patients were randomized to receive anastrozole and fulvestrant or anastrozole, fulvestrant, and gefitinib (AFG) for 3 weeks. After a second biopsy at 3 weeks, all patients received AFG for 4 months and surgery was done if the tumor was operable. The primary endpoint was best clinical response by RECIST criteria and secondary endpoints were toxicity and change in biomarkers. The study closed after 15 patients were enrolled because of slow accrual. Median patient age was 67 years and median clinical tumor size was 7 cm. Four patients had metastatic disease present. Three patients withdrew before response was assessed. In the remaining 12 patients, there were two complete clinical responses (17%), three partial responses (25%), five had stable disease (41%), and two (17%) had progressive disease. Most common adverse events were rash in four patients, diarrhea in four, joint symptoms in three, and abnormal liver function tests in three. There were no grade 4 toxicities and all toxicities were reversible. At 3 weeks, cell proliferation as measured by Ki-67 was significantly reduced in the AFG group (P value = 0.01), with a parallel reduction in the expression of the Cyclin D1 (P value = 0.02). RNA microarray data showed a corresponding decrease in the expression of cell cycle genes. These results suggest that AFG was an effective neoadjuvant therapy and consistently reduced proliferation in ER-positive tumors.

New and translational perspectives of oestrogen deprivation in breast cancer

Over the last 20 years, aromatase inhibitors have been developed to become a highly effective treatment strategy for treatment of hormone receptor positive breast cancer. Despite their success, poor response and resistance limit the effectiveness of these agents in up to 50% of patients. In recent years, studies using highly sensitive hormone assays have provided insight into the source of oestrogen production for the stimulation of oestrogen receptor positive breast cancer growth, suggesting that uptake from the circulation is likely to make a significant contribution to intratumoural oestradiol. To obtain insight into how tumours become resistant to oestrogen after aromatase inhibition, long term oestrogen deprivation of cultured cells has been used to mimic acquired resistance to aromatase inhibitors. This work has aided the selection of agents to rationally combine with aromatase inhibitors to combat resistance. Molecular profiling using genome-wide approaches has shed new light on the heterogeneity of responses to oestrogen deprivation and predictors of resistance in vivo. Testing new agents and combinations in short-term pre-surgical studies using biomarkers such as Ki67 is critical for increasing the rate at which new rational combinations can be assessed for efficacy.

Topoisomerase II alpha expression and the Ki-67 labeling index correlate with prognostic factors in estrogen receptor-positive and human epidermal growth factor type-2-negative breast cancer

BACKGROUND

Topoisomerase II alpha (Topo IIa) is involved in DNA replication and is a molecular target for anthracycline-based chemotherapy. The Ki-67 labeling index (LI) is an evaluation of tumor cell proliferation. The objective of this study was to evaluate relationships among Topo IIa expression, the Ki-67 LI, and prognostic factors in estrogen receptor (ER)-positive, human epidermal growth factor type-2 (HER2)-negative breast cancer.

MATERIALS AND METHODS

Seventy-one patients were diagnosed with ER-positive, HER2-negative breast cancer between July 2003 and December 2004. Formalin-fixed, paraffin-embedded tumor specimens were stained for Topo IIa expression and Ki-67 LI. We investigated the correlation of the level of Topo IIa expression and the Ki-67 LI with clinical factors such as age, tumor size, progesterone receptor status, nodal status, nuclear grade, and lymphovascular invasion (LVI).

RESULTS

Statistically significant differences were observed between Topo IIa overexpression, nuclear grade (p = 0.036), and LVI (p = 0.029). Topo IIa overexpression was statistically correlated with the Ki-67 LI (p < 0.0001). A statistically significant difference was observed between the Ki-67 LI and nuclear grade (p = 0.01). Survival analysis revealed the significant prognostic value of Ki-67 LI in patients with ER-positive, HER2-negative breast cancer (p = 0.003).

CONCLUSIONS

Ki-67 LI is a strong prognostic factor in ER-positive HER2-negative breast cancer. Topo IIa overexpression was significantly correlated with the Ki-67 LI, nuclear grade, and LVI. These findings suggest use of Topo IIa expression as a proliferation marker and a prognostic factor in ER-positive, HER2-negative breast cancer.

Use of dynamic contrast-enhanced MR imaging to predict survival in patients with primary breast cancer undergoing neoadjuvant chemotherapy

PURPOSE

To investigate whether early changes in vascular parameters determined with dynamic contrast material-enhanced magnetic resonance (MR) imaging after two cycles of neoadjuvant chemotherapy (NAC) are predictive of disease-free and overall survival in primary breast cancer.

MATERIALS AND METHODS

Institutional ethics approval and informed consent were obtained. Patients with primary breast cancer (median age, 45 years; age range, 22-70 years) recruited from January 2001 to September 2008 underwent dynamic contrast-enhanced MR imaging before and after two cycles of NAC. Quantitative and semiquantitative kinetic parameters were calculated, including the volume transfer constant (K(trans)) and the initial area under the gadolinium concentration-time curve over 60 seconds (IAUGC(60)). Cut points optimized to the receiver operating characteristic curve were used to dichotomize MR imaging data for Kaplan-Meier survival analysis. MR imaging parameters and known prognostic indicators in primary breast cancer were correlated with disease-free and overall survival by using the Cox proportional hazards model for univariate and multivariate analyses.

RESULTS

MR imaging was performed before (n = 62) and after (n = 58) two cycles of NAC. The median follow-up time was 43.9 months for disease-free survival and 60.3 months for overall survival. There were 28 recurrences; 26 patients had distant metastases (two had additional local recurrence) and two had local recurrence only. There were 20 deaths, all of which were related to breast cancer. At univariate analysis, progesterone receptor status, the type of surgery performed, higher posttreatment K(trans) (P = .048), and larger posttreatment IAUGC(60) (P = .035) were significant predictors of worse disease-free survival. At multivariate analysis, progesterone receptor status (P = .002) and mean transit time (P = .025) were significant predictors of disease-free survival. Univariate analysis showed that clinical tumor stage (P = .005), progesterone receptor status (P = .025), and type of surgery performed (P = .017) were significant predictors of overall survival. Higher posttreatment K(trans) (P = .043), larger IAUGC(60) (P = .029), and larger tumor size at posttreatment MR imaging were predictive of worse overall survival (P = .018). Of these variables, K(trans) remained an independent indicator of overall survival (P = .038).

CONCLUSION

Higher posttreatment tumor vascularization as depicted with dynamic contrast-enhanced MR imaging may be associated with higher recurrence and lower survival rates. Dynamic contrast-enhanced MR imaging parameters, in conjunction with traditional prognostic factors, have the potential to be prognostic biomarkers for disease-free and overall survival in primary breast cancer.

Association between breast cancer subtypes and response to neoadjuvant anastrozole

Considerable heterogeneity exists amongst oestrogen receptor positive (ER+ve) breast cancer in both its molecular profile and response to therapy. Attempts to better define variation amongst breast tumours have led to the definition of four main "intrinsic" subtypes of breast cancer with two of these classes, Luminal A and B, composed almost entirely of ER+ve cancers. In this study we set out to investigate the significance of intrinsic subtypes within a group of ER+ve breast cancers treated with neoadjuvant anastrozole. RNA from tumour biopsies taken from 104 postmenopausal women before and after 2 weeks treatment with anastrozole was analyzed on Illumina 48K microarrays. Gene-expression based subtypes and risk of relapse (ROR) scores for tumours pre- and post-treatment were determined using the PAM50 method. Amongst pre-treatment samples, all intrinsic subtypes were found to be present, although luminal groups were represented most highly. Luminal A and B tumours obtained similar benefit from treatment, as measured by the proportional fall in the proliferation marker Ki67 upon treatment (mean suppression=75.5% vs 75.7%). Tumours classified as basal and Her2-like showed poor reductions in Ki67 upon treatment. Residual Ki67 staining after two weeks remained higher in the Luminal B group. ROR score was significantly associated with anti-proliferative response to AI and with clinical response. These results suggest that in the short-term, Luminal A and B tumours may gain similar benefit from an AI but that the higher residual Ki67 level seen in Luminal B is indicative of poorer long term outcome.

Prediction of outcome of early ER+ breast cancer is improved using a biomarker panel, which includes Ki-67 and p53

Background:

The aim of this study is to determine whether immunohistochemical (IHC) assessment of Ki67 and p53 improves prognostication of oestrogen receptor-positive (ER+) breast cancer after breast-conserving therapy (BCT). In all, 498 patients with invasive breast cancer from a randomised trial of BCT with or without tumour bed radiation boost were assessed using IHC.

Methods:

The ER+ tumours were classified as ‘luminal A’ (LA): ER+ and/or PR+, Ki-67 low, p53−, HER2− or ‘luminal B’ (LB): ER+ and/or PR+and/or Ki-67 high and/or p53+ and/or HER2+. Kaplan–Meier and Cox proportional hazards methodology were used to ascertain relationships to ispilateral breast tumour recurrence (IBTR), locoregional recurrence (LRR), distant metastasis-free survival (DMFS) and breast cancer-specific survival (BCSS).

Results:

In all, 73 patients previously LA were re-classified as LB: a greater than four-fold increase (4.6–19.3%) compared with ER, PR, HER2 alone. In multivariate analysis, the LB signature independently predicted LRR (hazard ratio (HR) 3.612, 95% CI 1.555–8.340, P=0.003), DMFS (HR 3.023, 95% CI 1.501–6.087, P=0.002) and BCSS (HR 3.617, 95% CI 1.629–8.031, P=0.002) but not IBTR.

Conclusion:

The prognostic evaluation of ER+ breast cancer is improved using a marker panel, which includes Ki-67 and p53. This may help better define a group of poor prognosis ER+ patients with a greater probability of failure with endocrine therapy.

Differentially expressed genes in window trials are influenced by the wound-healing process: lessons learned from a pilot study with anastrozole

BACKGROUND

Perioperative window trials provide an opportunity to obtain intact tumor samples at two different time-points for evaluation of potential surrogate biomarkers. We report results of a pilot trial designed to determine if treatment-mediated changes in gene expression can be detected in formalin-fixed paraffin-embedded (FFPE) samples after 10-d exposure to anastrozole in estrogen receptor (ER)-positive breast cancer compared with untreated controls.

METHODS

Paired tumor samples (biopsy, surgical) were obtained from 26 postmenopausal women with ER-positive breast cancer. Patients were assigned anastrozole (1 mg/d) for 10 d immediately prior to surgery (13 cases) or no treatment (13 controls). Five hundred two cancer-related genes were examined by the Illumina cDNA-mediated annealing, selection, extension, and ligation, FFPE cDNA array (moderated t-test, P ≤ 0.005). Surrogate biomarkers reflecting changes in gene expression were examined by immunohistochemistry (Wilcoxon rank-based test, P < 0.05).

RESULTS

Sufficient RNA was available from 19 paired samples (8 controls, 11 cases). Frozen tissue and FFPE showed good correlation (r = 0.82). Within each group, 18 genes, reflecting roles in proliferation, angiogenesis, and apoptosis, showed differential expression from biopsy to surgery (P < 0.005). Estrogen-related genes were dysregulated in the treated group only. A reduction in Ki-67 was observed in 7 (54%) treated cases and in 1 (7.7%) control patient.

CONCLUSIONS

10-d exposure to anastrozole resulted in dysregulation of 18/502 cancer-related genes, and Ki-67 was reduced in 54% of cases. FFPE samples demonstrated good correlation with frozen samples. However, changes in gene expression and increased Ki-67 in the control group suggest local effects of wound healing may represent a confounding factor in the interpretation of perioperative window trials.

Lapatinib activity in premalignant lesions and HER-2-positive cancer of the breast in a randomized, placebo-controlled presurgical trial

Dual epidermal growth factor receptor (EGFR) and HER2 targeting with the tyrosine kinase inhibitor lapatinib is approved for treating advanced HER2-positive breast cancer and can prevent estrogen receptor (ER)-negative mammary tumors in HER2 transgenic mouse models. Ki-67 labeling index (LI) has prognostic and predictive value and can be used to screen drugs' therapeutic and preventive potential in a clinical model of short-term presurgical therapy of breast cancer. We conducted a randomized, placebo-controlled trial of lapatinib (1500 mg/d) administered orally for three weeks between biopsy and surgery in 60 women with HER-2-positive breast cancer to assess lapatinib biomarker (including the primary endpoint, Ki-67 LI) and clinical activity in invasive breast cancer, adjacent ductal intraepithelial neoplasia (DIN, which comprises ductal carcinoma in situ and atypical ductal hyperplasia), and distant ductal hyperplasia without atypia (DH). Ki-67 LI increased progressively in association with disease stage, increasing in the placebo arm, for example, by medians of 3% in DH to 20% in DIN to 30% in invasive cancer. Ki-67 LI in cancer tissue decreased by a mean (±SD) of 9.3% (±34.2) in the lapatinib arm and increased by 15.1% (±30.9) in the placebo arm (P = 0.008). Compared with placebo, lapatinib reduced Ki-67 significantly more in ER-negative tumors (by 34.8%; P = 0.01) but not significantly more in ER-positive tumors (by 12.3%; P = 0.2) and reduced Ki-67 more (nonsignificantly) in cytosol PTEN-overexpressing tumors (P = 0.057). The prevalence of DIN in post-treatment surgical specimens of both arms was similar (70%-76%), with a median Ki-67 of 15% (range, 5%-35%) on lapatinib versus 20% (5%-60%) on placebo (P = 0.067). The prevalence of DH also was similar in both arms (>90%), with a median Ki-67 of 1% (1%-7%) on lapatinib versus 3% (1%-5%) on placebo (P = 0.006). Other results of lapatinib versus placebo, respectively, were as follows: Median tumor diameter at surgery of 18 mm (11 mm-57 mm) versus 24 mm (10 mm-37 mm; P = 0.009); partial response of 13.6% versus 3.7%, stable disease of 59.1% versus 40.7%, and progression of 27.3% versus 55.6% (P-trend = 0.035). In conclusion, short-term lapatinib decreased cell proliferation in DIN, DH, and invasive HER-2-positive (especially ER-negative) breast cancer, thus providing the rationale for further clinical development of lapatinib for breast cancer prevention in high-risk patients, including those with HER-2-positive DIN.

Randomized phase II neoadjuvant comparison between letrozole, anastrozole, and exemestane for postmenopausal women with estrogen receptor-rich stage 2 to 3 breast cancer: clinical and biomarker outcomes and predictive value of the baseline PAM50-based intrinsic subtype--ACOSOG Z1031

PURPOSE

Preoperative aromatase inhibitor (AI) treatment promotes breast-conserving surgery (BCS) for estrogen receptor (ER)-positive breast cancer. To study this treatment option, responses to three AIs were compared in a randomized phase II neoadjuvant trial designed to select agents for phase III investigations.

PATIENTS AND METHODS

Three hundred seventy-seven postmenopausal women with clinical stage II to III ER-positive (Allred score 6-8) breast cancer were randomly assigned to receive neoadjuvant exemestane, letrozole, or anastrozole. The primary end point was clinical response. Secondary end points included BCS, Ki67 proliferation marker changes, the Preoperative Endocrine Prognostic Index (PEPI), and PAM50-based intrinsic subtype analysis.

RESULTS

On the basis of clinical response rates, letrozole and anastrozole were selected for further investigation; however, no other differences in surgical outcome, PEPI score, or Ki67 suppression were detected. The BCS rate for mastectomy-only patients at presentation was 51%. PAM50 analysis identified AI-unresponsive nonluminal subtypes (human epidermal growth factor receptor 2 enriched or basal-like) in 3.3% of patients. Clinical response and surgical outcomes were similar in luminal A (LumA) versus luminal B tumors; however, a PEPI of 0 (best prognostic group) was highest in the LumA subset (27.1% v 10.7%; P = .004).

CONCLUSION

Neoadjuvant AI treatment markedly improved surgical outcomes. Ki67 and PEPI data demonstrated that the three agents tested are biologically equivalent and therefore likely to have similar adjuvant activities. LumA tumors were more likely to have favorable biomarker characteristics after treatment; however, occasional paradoxical increases in Ki67 (12% of tumors with > 5% increase after therapy) suggest treatment-resistant cells, present in some LumA tumors, can be detected by post-treatment profiling.

New developments in hormone receptor-positive disease

Of more than one million women diagnosed with breast cancer each year, approximately 700,000 have hormone receptor (HR)(+) disease. Although endocrine therapy has revolutionized breast cancer management and substantially improved outcomes in these patients, the optimal management of these patients remains a significant challenge. For instance, the threshold for adding adjuvant chemotherapy is a topic of continuing debate, and the most effective regimens that include endocrine therapy and chemotherapy are still under debate as well. Tumor markers, such as Ki-67, and host markers, such as cytochrome P450 2D6, are being studied as potential tools to offer more tailored adjuvant endocrine therapy. Current research suggests that luminal A and luminal B cancers are two completely different diseases, and work is being performed to better distinguish between these two disease types and deliver more effective therapy to individual patients. This article addresses these important outstanding issues with respect to HR(+) disease.

Clinical significance of Ki-67 in neoadjuvant chemotherapy for primary breast cancer as a predictor for chemosensitivity and for prognosis

BACKGROUND

Neoadjuvant chemotherapy (NAC) is one of the main strategies for patients with locally advanced breast cancer. In recent years several biological markers such as estrogen receptor (ER), progesterone receptor (PgR), and HER2 were discovered to be predictive factors for the effectiveness of NAC to help individualize treatment. In this retrospective study, we focused on Ki-67 as a biological marker and examined the correlation between Ki-67 and chemosensitivity, and the prognosis after the start of treatment.

PATIENTS AND METHODS

Between July 1996 and March 2008, 148 patients with tumors ≥ 3 cm in diameter or lymph node metastases received NAC and surgery. The items investigated were ER/PgR and Ki-67 from core needle biopsy. The treatment regimens were EC in 36 cases, ET in 51 cases, and FEC-DOC in 61 cases. The patients with FEC-DOC regimen had smaller tumors and higher Ki-67 values than the others.

RESULTS

Clinical response (cCR + cPR) was 79.7%, and the pathological complete response (pCR) was 14.2%. Multivariate analysis revealed that Ki-67 was significantly related to pCR. Moreover, there was no pathological responder in cases with Ki-67 < 25%. The Ki-67 values significantly decreased after NAC (median from 45.0 to 17.5%). Patients with cCR had significantly lower Ki-67 values after NAC than those with cPR, cSD, and cPD. There was a significant difference in the Ki-67 value in terms of the presence and the absence of recurrence (median 26.0% with recurrence vs. 12% without recurrence). The disease-free survival (DFS) rate after the start of treatment was significantly higher in the patients with Ki-67 < 12% after NAC than those with Ki-67 ≥ 12%.

CONCLUSION

The Ki-67 value before NAC was a significant predictive factor for the effectiveness of NAC. The Ki-67 values after NAC significantly decreased and correlated with clinical response and DFS. Therefore, higher Ki-67 values (≥ 25%) before NAC as well as lower values (<12%) after NAC might be clinically significant for treating patients.

Ki67 index changes, pathological response and clinical benefits in primary breast cancer patients treated with 24 weeks of aromatase inhibition

Aromatase inhibitor shows efficacy for hormone receptor positive postmenopausal breast cancer. We evaluated the activity of 24 weeks of aromatase inhibition with exemestane for primary breast cancer in a neoadjuvant setting. Patients with stage II/IIIA invasive breast cancer with estrogen receptor (ER) and/or progesterone receptor (PgR)-positive status were eligible. Primary endpoints were objective response rate (ORR) and safety. A steroidal aromatase inhibitor exemestane of 25 mg/day was administered for 16 weeks with an 8-week extension. Secondary endpoints were rates of breast-conserving surgery (BCS), and change of Ki67 index and ER/PgR expression in central laboratory analyses. Between March 2006 and December 2007, 116 patients were enrolled. Among those, 102 patients completed 24 weeks of administration. The ORR was 47% (55/116) at Week 16 and 51% (59/116) at Week 24, respectively. No serious toxicity was seen. ORR was associated with ER Allred scores but not with PgR scores. The significant reduction in Ki67 index was confirmed. No progression was experienced in tumors with less than 15% Ki67 index. Pathological response was observed in 28 (30%) of 94 evaluated cases. No statistical correlation between pre-treatment Ki67 index and pathological response was detected; however, a trend of correlation was found between the post-treatment preoperative endocrine prognostic index (PEPI), a prognostic score and the pathological response. At diagnosis, 59 patients (51%) would have required mastectomy but 40 patients were converted to BCS, showing an increase in the rate of BCS (77%). The 24-week aromatase inhibition provided preferable clinical benefits with significant reduction in Ki67 index. More precise mechanisms of the response need to be investigated.

Hormone receptor status rather than HER2 status is significantly associated with increased Ki-67 and p53 expression in triple-negative breast carcinomas, and high expression of Ki-67 but not p53 is significantly associated with axillary nodal metastasis in triple-negative and high-grade non-triple-negative breast carcinomas

Triple-negative (TN) breast carcinoma is associated with a higher recurrence rate and shorter survival and lacks the benefit of specific therapy. TN tumors usually express high levels of Ki-67 and p53 that are considered prognostic markers for breast cancer. We compared Ki-67 and p53 expression between TN and high-grade non-TN invasive carcinomas in a total of 214 cases and investigated an association between their expression and axillary nodal metastasis in these tumors. Our findings demonstrate that TN tumors are associated with significantly higher expression of Ki-67 and p53 compared with non-TN tumors, which may contribute to the poorer prognosis in TN tumors. Hormone receptor negativity rather than HER2 negativity is associated with the significantly increased Ki-67 and p53 expression in TN tumors. Furthermore, a high expression level of Ki-67 but not p53 is more likely to be associated with axillary nodal metastasis in these cases.

Endocrine therapy, new biologicals, and new study designs for presurgical studies in breast cancer

The preoperative setting is increasingly popular for the clinical investigation of hormonal agents and new biological drugs. The effectiveness of endocrine agents is well established for estrogen receptor-positive disease, and the emphasis in preoperative studies is on their combination with agents targeted at resistance mechanisms over 3 or more months. New agents are also being assessed for early evidence of clinical efficacy in shorter-term window-of-opportunity studies. The establishment of Ki67 as an intermediate marker of treatment benefit and of long-term outcome, with endocrine drugs, provides the opportunity for new trial designs with Ki67 as the primary endpoint. The PeriOperative Endocrine Therapy for Individualizing Care (POETIC) trial is randomizing (2:1) 4000 estrogen receptor-positive patients to 2 weeks presurgical treatment with a nonsteroidal aromatase inhibitor or no presurgical treatment. It provides a unique opportunity for detailed study of the determinants of response and resistance to estrogen deprivation as well as testing the role of presurgical therapy for improved biomarker-based estimates of prognosis.

Prognostic significance of Ki67 index after neoadjuvant chemotherapy in breast cancer

PURPOSE

Recently, Ki67 index (cell proliferation marker) has been attracting a considerable attention as a prognostic factor in breast cancer but the prognostic significance of Ki67 after neoadjuvant chemotherapy (NAC) has rarely been examined.

EXPERIMENTAL DESIGN

Primary breast cancer patients (n = 102) treated with NAC (sequential paclitaxel 12 cycles (q1w) and 5-FU/epirubicin/cyclophosphamide 4 cycles (q3w)) were recruited in the study. Ki67, estrogen receptor (ER) and progesterone receptor (PR) and breast cancer resistant protein (BCRP) and P-glycoprotein were determined by immunohistochemistry and HER2 was determined by FISH in tumor tissues obtained before and after NAC, and their association with patient prognosis (relapse-free survival) was examined.

RESULTS

Of the 102 patients, pCR was achieved in 30 (29.4%). In the 72 non-pCR patients, Ki67 index significantly (P < 0.001) decreased after NAC. Ki67 index after NAC, but not Ki67 index before NAC, was significantly associated with a patient prognosis (P = 0.022). Multivariate analysis has shown that Ki67 index after NAC is a marginally significant (P = 0.05) prognostic factor and that other biomarkers including ER, PR, BCRP, and P-glycoprotein before and after NAC are not significant.

CONCLUSIONS

Ki67 after NAC, but not before NAC, is prognostic in breast cancer patients, and might be clinically useful in the prognosis prediction of patients who do not achieve pCR after NAC. On the other hand, BCRP and P-glycoprotein before and after NAC are unlikely to be useful as prognostic factors in these patients.

Translating cancer research into targeted therapeutics

The emphasis in cancer drug development has shifted from cytotoxic, non-specific chemotherapies to molecularly targeted, rationally designed drugs promising greater efficacy and less side effects. Nevertheless, despite some successes drug development remains painfully slow. Here, we highlight the issues involved and suggest ways in which this process can be improved and expedited. We envision an increasing shift to integrated cancer research and biomarker-driven adaptive and hypothesis testing clinical trials. The goal is the development of specific cancer medicines to treat the individual patient, with treatment selection being driven by a detailed understanding of the genetics and biology of the patient and their cancer.

Reduction in Ki-67 in benign breast tissue of high-risk women with the lignan secoisolariciresinol diglycoside

Preclinical and correlative studies suggest reduced breast cancer with higher lignan intake or blood levels. We conducted a pilot study of modulation of risk biomarkers for breast cancer in premenopausal women after administration of the plant lignan secoisolariciresinol given as the diglycoside (SDG). Eligibility criteria included regular menstrual cycles, no oral contraceptives, a >3-fold increase in 5-year risk, and baseline Ki-67 of ≥2% in areas of hyperplasia in breast tissue sampled by random periareolar fine-needle aspiration (RPFNA) during the follicular phase of the menstrual cycle. SDG (50 mg/d) was given for 12 months, followed by repeat RPFNA. The primary end point was change in Ki-67. Secondary end points included change in cytomorphology, mammographic breast density, serum bioavailable estradiol and testosterone insulin-like growth factor-I and IGF-binding protein-3, and plasma lignan levels. Forty-five of 49 eligible women completed the study with excellent compliance (median = 96%) and few serious side effects (4% grade 3). Median plasma enterolactone increased ∼9-fold, and total lignans increased 16-fold. Thirty-six (80%) of the 45 evaluable subjects showed a decrease in Ki-67, from a median of 4% (range, 2-16.8%) to 2% (range, 0-15.2%; P < 0.001, Wilcoxon signed rank test). A decrease from baseline in the proportion of women with atypical cytology (P = 0.035) was also observed. Based on favorable risk biomarker modulation and lack of adverse events, we are initiating a randomized trial of SDG versus placebo in premenopausal women.

Post-treatment tumor gene expression signatures are more predictive of treatment outcomes than baseline signatures in breast cancer

OBJECTIVE

Tumor gene expression signatures have been used to classify, prognosticate, and predict chemotherapy sensitivity in breast cancer, although almost all efforts have been focused on the unchallenged baseline tumor. Most cancer patients receive systemic therapy, and exposure to drug may modify the tumor's short-term and long-term outcomes. Drug-induced tumor gene signatures may thus be more predictive of treatment outcomes than the unperturbed tumor gene signatures.

METHODS

Using a set of 47 breast cancer patients, we obtained paired prechemotherapy and postchemotherapy tumor biopsies and developed gene panels of baseline tumor (T1), postchemotherapy tumor (T2), and chemotherapy-induced relative change signatures (TDelta) to predict pathological response and progression-free survival (PFS). The signatures were validated in two independent test sets with paired prechemotherapy and postchemotherapy tumor samples, comprising of 18-20 patients each.

RESULTS

T2 and TDelta were superior to T1 signatures in predicting for PFS (area under the curve of receiver operating characteristic 0.770 and 0.660 vs. 0.530) and pathological response (area under the curve of receiver operating characteristic 0.631 and 0.462 vs. 0.446) in the validation sets. In multivariate analysis for PFS with other clinical predictors, T2, but not T1, signatures remained as significant independent predictors.

CONCLUSION

Postchemotherapy tumor gene signatures outperformed baseline signatures and clinical predictors in predicting for pathological response and PFS, independent of clinical and pathological response to chemotherapy. Drug-induced tumor gene signatures may be more informative than unchallenged signatures in predicting treatment outcomes. These findings challenge the current practice of relying only on the baseline tumor to predict outcome, which overlooks the contributions of therapeutic interventions.

Neoadjuvant endocrine therapy in primary breast cancer: indications and use as a research tool

Neoadjuvant endocrine therapy has been increasingly employed in clinical practice to improve surgical options for postmenopausal women with bulky hormone receptor-positive breast cancer. Recent studies indicate that tumour response in this setting may predict long-term outcome of patients on adjuvant endocrine therapy, which argues for its broader application in treating hormone receptor-positive disease. From the research perspective, neoadjuvant endocrine therapy provides a unique opportunity for studies of endocrine responsiveness and the development of novel therapeutic agents.

Prognostic significance of Ki-67 labeling index after short-term presurgical tamoxifen in women with ER-positive breast cancer

BACKGROUND

Studies have shown that Ki-67 response after short-term neoadjuvant aromatase inhibitors may predict recurrence in postmenopausal breast cancer, whereas its prognostic effect in premenopausal women is unknown.

PATIENTS AND METHODS

We compared the prognostic and predictive value of baseline and post-treatment Ki-67 in 120 pre- and postmenopausal women with early-stage estrogen receptor-positive breast cancer who participated in a 4-week presurgical trial of tamoxifen.

RESULTS

After 7.2 years of follow-up, women with post-treatment Ki-67 in the second (14%-19%), third (20%-29%) and top (≥30%) quartiles had a recurrence hazard ratio of 2.92 [95% confidence interval (CI) 0.95-8.96], 4.37 (1.56-12.25) and 6.05 (2.07-17.65), respectively, as compared with those in the bottom quartile (<14%) (P-trend = 0.001). The risk of invasive disease recurrence was 2.2% (95% CI 0.9-5.0) per point increase in baseline Ki-67 (P-trend = 0.076) and 5.0% (95% CI 2.3-7.7) per point increase in post-tamoxifen Ki-67 (P-trend < 0.001). The risk of death was 5.5 (95% CI 1.26-23.16) times higher in patients with post-drug Ki-67 ≥20% than in those with Ki-67 <20% (P-trend = 0.006).

CONCLUSIONS

Ki-67 response after short-term neoadjuvant tamoxifen is a good predictor of recurrence-free survival and overall survival, further supporting its use as surrogate biomarker to personalize adjuvant treatment and to screen novel drugs cost-effectively.

Ki-67 as a prognostic marker according to breast cancer subtype and a predictor of recurrence time in primary breast cancer

The choice of adjuvant systemic therapy is based on targeted therapy in line with the St. Gallen Consensus meeting. In addition to the traditional parameters, the panel recommended the use of proliferation markers and multigene assays. The purpose of the present study was to evaluate the clinical significance of proliferative activity using the Ki-67 index as a prognostic marker and as a predictor of recurrence time in breast cancer patients. The Ki-67 index was measured in 3,652 cases with primary breast cancer from 1987 to 2009. Out of these patients, 2,638 cases were evaluated simultaneously for estrogen receptor, progesterone receptor and HER2 from 1997, and these were analyzed as a prognostic factor according to their subtypes. The Ki-67 index exhibited a wide range of 1-99%, with a median of 20%, and cases were divided into 2 or 3 index groups; <20% and ≥20% (and ≥50%). The median Ki-67 index of tumors with luminal A was 17%, and that of luminal B type tumors was 29%. The Ki-67 index of HER2 tumors was 40% and that of triple negative tumors was 50%. A higher Ki-67 index significantly correlated with a higher grade of malignancy. Patients with a higher Ki-67 index had significantly lower disease-free survival (DFS) and overall survival rates. Moreover, there was a significant difference in the recurrence time. Multivariate analysis revealed that the Ki-67 index was a significant factor for DFS, irrespective of nodal status, and that Ki-67 was a significant marker only in luminal A type tumors. Furthermore, luminal A type cases with high Ki-67 had a similar DFS as the luminal B type cases. A higher Ki-67 index (≥20%) significantly correlated with other biological markers, poorer prognosis and early recurrence, particularly in luminal A type tumors. It is important to take the Ki-67 index into consideration in the treatment and follow-up of breast cancer patients.

Early metabolic response to neoadjuvant letrozole, measured by FDG PET/CT, is correlated with a decrease in the Ki67 labeling index in patients with hormone receptor-positive primary breast cancer: a pilot study

PURPOSE

To assess whether the early metabolic response evaluated by (18)F-fluorodeoxy-glucose positron emission combined with computed tomography (FDG PET/CT) predicts the morphological, pathological, and cell-cycle responses to neoadjuvant endocrine therapy of hormone receptor-positive primary breast cancer.

STUDY DESIGN

Eleven patients (12 tumors) with estrogen receptor-positive (Allred score 7 or 8) primary breast cancer were enrolled. All patients received a daily dose (2.5 mg) of letrozole for 12 weeks followed by surgery. Sequential FDG PET/CT scans were performed before treatment (baseline), at 4 weeks after the initiation of endocrine therapy (PET2), and prior to surgery (PET3). Tumors showing a 40% or more reduction and those showing a less than 40% reduction in the standardized uptake value maximum (SUV(max)) at PET2 compared with the baseline PET were defined as metabolic responders and metabolic nonresponders, respectively. Change in tumor size as measured by ultrasound (morphological response), pathological response, and change in the Ki67 labeling index in tumor tissue (cell-cycle response) during the neoadjuvant letrozole therapy were compared between the metabolic responders and nonresponders.

RESULTS

The average decreases in SUV(max) at PET2 compared with the baseline PET in the metabolic responders (n = 6) and the metabolic nonresponders (n = 6) were 60.9% (±21.3 SD) and 14.2% (±12.0 SD), respectively. At PET3 compared with the baseline PET, the metabolic responders showed a significantly higher decrease of 64.5% (±18.7 SD) (p = 0.0004), whereas the nonresponders showed a nonsignificant decrease of 16.7% (±14.1 SD) (p = 0.06). The morphological and pathological responses after letrozole therapy did not differ between the metabolic responders and nonresponders. The metabolic responders showed a marked decrease in the Ki67 labeling index at 2 weeks after the initiation of treatment (62.9%, ±35.9 SD, p = 0.04) and at surgery (91.7%, ±10.7 SD, p = 0.03) compared with the baseline values. In contrast, metabolic nonresponders showed no significant change in the Ki67 index either after 2 weeks of therapy or at surgery.

CONCLUSION

Cell-cycle response monitored by the Ki67 labeling index correlates with metabolic response monitored by tumor SUV(max). Monitoring of tumor SUV(max) using FDG PET/CT may be feasible to predict cell-cycle response to neoadjuvant endocrine therapy of primary breast cancer.