Sequential estrogen receptor determinations from primary breast cancer and at relapse: prognostic and therapeutic relevance. The International Breast Cancer Study Group (formerly Ludwig Group)

Novel applications of molecular imaging to guide breast cancer therapy

The goals of precision oncology are to provide targeted drug therapy based on each individual’s specific tumor biology, and to enable the prediction and early assessment of treatment response to allow treatment modification when necessary. Thus, precision oncology aims to maximize treatment success while minimizing the side effects of inadequate or suboptimal therapies. Molecular imaging, through noninvasive assessment of clinically relevant tumor biomarkers across the entire disease burden, has the potential to revolutionize clinical oncology, including breast oncology. In this article, we review breast cancer positron emission tomography (PET) imaging biomarkers for providing early response assessment and predicting treatment outcomes. For 2-¹⁸fluoro-2-deoxy-D-glucose (FDG), a marker of cellular glucose metabolism that is well established for staging multiple types of malignancies including breast cancer, we highlight novel applications for early response assessment. We then review current and future applications of novel PET biomarkers for imaging the steroid receptors, including the estrogen and progesterone receptors, the HER2 receptor, cellular proliferation, and amino acid metabolism.

Update on Quantitative Imaging for Predicting and Assessing Response in Oncology

Molecular imaging has revolutionized clinical oncology by imaging-specific facets of cancer biology. Through noninvasive measurements of tumor physiology, targeted radiotracers can serve as biomarkers for disease characterization, prognosis, response assessment, and predicting long-term response/survival. In turn, these imaging biomarkers can be utilized to tailor therapeutic regimens to tumor biology. In this article, we review biomarker applications for response assessment and predicting long-term outcomes. ¹⁸F-fluorodeoxyglucose (FDG), a measure of cellular glucose metabolism, is discussed in the context of lymphoma and breast and lung cancer. FDG has gained widespread clinical acceptance and has been integrated into the routine clinical care of several malignancies, most notably lymphoma. The novel radiotracers 16α-¹⁸F-fluoro-17β-estradiol and ¹⁸F-fluorothymidine are reviewed in application to the early prediction of response assessment of breast cancer. Through illustrative examples, we explore current and future applications of molecular imaging biomarkers in the advancement of precision medicine.

Synchronous bilateral breast cancer: A case report of heterogeneous estrogen receptor status

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Hormone receptors are established biomarkers for treatment and prognosis of patients with breast cancer.

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Receptor status change is dynamic and unstable throughout tumour progression and during advance stage disease.

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Four mechanisms of breast cancer heterogeneity have been described which includes differentiation of state of cell origin, cell plasticity, genetic evolution of cancer and tumour microenvironment.

Introduction

Tumour heterogeneity is important in the management of breast cancer. Hormone receptors are established biomarkers for treatment and prognosis of patients with breast cancer.

There are three immunohistochemical biomarkers: estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor 2 (HER2).

We explore whether heterogeneity in hormone receptor status in synchronous bilateral breast alters therapeutic management.

Case presentation

This case details a 54 year old woman who was referred to our clinic by her general practitioner for investigation of bilateral breast pain that she had for 6 months.

On clinical examination pathological nodes were palpated in bilateral axilla. There was left sided nipple inversion with a palpable mass in the upper outer quadrant of approximately 3 cm diameter.

On examination of the right breast there was skin tethering of the nipple and 3 masses were palpated, the largest being in the upper inner quadrant at 5 cm diameter.

Ultrasound and mammography of bilateral breasts demonstrated advanced bilateral breast cancer with axillary node metastases.

Core biopsies demonstrated invasive carcinoma. The right breast lesion was ER negative whilst the left breast lesion was ER positive.

Discussion

In patients with synchronous bilateral breast cancer ER discordance in patients have been associated with higher mortality than ER concordant positive patients and lower mortality than ER concordant negative patients within the first 5 years of surveillance [1].

Conclusion

Heterogeneity in hormone receptor status alters the therapeutic management of patients with synchronous bilateral breast cancer. Both hormone therapy and chemotherapy should be considered in these patients.

It is of utmost importance to evaluate the tumor receptor status in cases of synchronous bilateral breast tumour and to assess for change in relation to tumour progression or treatment. Further study in the status change of receptors could open up new treatment modalities.

Development of Companion Diagnostics

The goal of individualized and targeted treatment and precision medicine requires the assessment of potential therapeutic targets to direct treatment selection. The biomarkers used to direct precision medicine, often termed companion diagnostics, for highly targeted drugs have thus far been almost entirely based on in vitro assay of biopsy material. Molecular imaging companion diagnostics offer a number of features complementary to those from in vitro assay, including the ability to measure the heterogeneity of each patient's cancer across the entire disease burden and to measure early changes in response to treatment. We discuss the use of molecular imaging methods as companion diagnostics for cancer therapy with the goal of predicting response to targeted therapy and measuring early (pharmacodynamic) response as an indication of whether the treatment has "hit" the target. We also discuss considerations for probe development for molecular imaging companion diagnostics, including both small-molecule probes and larger molecules such as labeled antibodies and related constructs. We then describe two examples where both predictive and pharmacodynamic molecular imaging markers have been tested in humans: endocrine therapy for breast cancer and human epidermal growth factor receptor type 2-targeted therapy. The review closes with a summary of the items needed to move molecular imaging companion diagnostics from early studies into multicenter trials and into the clinic.

Comparison of Predictive Immunohistochemical Marker Expression of Primary Breast Cancer and Paired Distant Metastasis using Surgical Material: A Practice-Based Study

Parallel studies of primary breast carcinomas and corresponding distant metastases samples reveal considerable differences. Our aim was to highlight this issue from another perspective and provide further data based on 98 patient samples: 69 primary breast carcinoma and 85 distant metastases from bone, central nervous system (CNS) and lung (56 paired). Two independent series of immunohistochemical reactions with different antibodies for estrogen receptor (ER), progesterone receptor (PgR) and human epidermal growth factor receptor 2 (Her2), along with HER2 fluroscence in situ hybridization (FISH) were performed on tissue microarrays to classify breast carcinoma and distant metastases samples into Luminal A, Luminal B-proliferating, Luminal B-HER2+, HER2+ and triple negative (TNBC) surrogate breast cancer groups. Correlation and agreement between the two assessments of ER and PgR were fair-to-moderate, and almost perfect for HER2 and Ki67. There was 40% discordance concerning immunophenotype between breast carcinomas and distant metastases. Most common metastatic site of ER+ breast carcinoma was the skeletal system (59.2%), whereas that of TNBCs was the CNS (58.8%) and lungs (23.5%). Distant metastases in bones were mostly luminal (54.3%), in the CNS, Luminal B (53.2%), and in the lung, TNBC (37.5%). The change of drugable properties of primary breast cancers in the respective bone and CNS metastases suggests that characterization of the metastasis is necessary for appropriate treatment planning.

Molecular imaging using PET for breast cancer

Molecular imaging can visualize the biological processes at the molecular and cellular levels in vivo using certain tracers for specific molecular targets. Molecular imaging of breast cancer can be performed with various imaging modalities, however, positron emission tomography (PET) is a sensitive and non-invasive molecular imaging technology and this review will focus on PET molecular imaging of breast cancer, such as FDG-PET, FLT-PET, hormone receptor PET, and anti-HER2 PET.

Change in estrogen receptor, HER2, and Ki-67 status between primary breast cancer and ipsilateral breast cancer tumor recurrence

INTRODUCTION

Changes in the biological marker status between primary and recurrent tumors are observed in breast cancer. However, their clinical significance is still uncertain, especially for patients with ipsilateral breast tumor recurrence (IBTR) after breast-conserving surgery.

PATIENTS AND METHODS

A total of 117 patients with IBTR without distant metastases were enrolled in this study. All patients were examined for estrogen receptor (ER), HER2, and Ki-67 in both the primary tumors and paired IBTR. We evaluated the impact of changes in these biomarkers between primary tumors and IBTR on the prognosis after IBTR.

RESULTS

There were no associations of changes in the ER, HER2 status with distant disease-free survival (DDFS) after surgical resection of IBTR, whereas the change in the Ki-67 status between the primary tumors and IBTR was significantly correlated with DDFS (unadjusted: p = 0.0094; adjusted: p = 0.013). Patients in the "increased or remained high" Ki-67 group had a significantly shorter DDFS than those in the "decreased or remained low" Ki-67 group (5-year DDFS: 55.5 vs. 79.3%, respectively, p = 0.0084 by log-rank test).

CONCLUSION

An increased or persistently high Ki-67 status in the IBTR was significantly correlated with a poorer prognosis after IBTR.

Heterogeneity in hormone-receptor status and survival outcomes among women with synchronous and metachronous bilateral breast cancers

To examine whether discordance in the hormone-receptor status predicts clinical outcomes in patients with bilateral synchronous (SBC) or metachronous breast cancer (MBC), we analyzed data from the Surveillance, Epidemiology, and End Results program (1998-2011) using Cox models. After excluding 10,231 patients with missing data on hormone receptors in at least one tumor, 4403 SBC and 7159 MBC were included in the study. Among SBC cases, patients with estrogen receptor (ER)-discordant tumors had higher mortality risk (multivariable-adjusted hazard ratio [HR] = 1.96, 95% confidence interval [CI] 1.60-2.40) than patients with ER concordant-positive tumors, whereas patients with ER concordant-negative tumors had the highest risk (HR = 2.49, 95% CI 2.03-3.07). Among MBC cases, patients with a positive-to-negative change in ER status (HR = 1.32, 95% CI: 1.08-1.62) or ER concordant-negative tumors (HR = 1.48, 95% CI: 1.19-1.85) had worse survival than patients with ER concordant-positive tumors. In conclusion, discordance in the hormone-receptor status was an independent predictor of survival outcomes.

Discordance in hormone receptor status among primary, metastatic, and second primary breast cancers: biological difference or misclassification?

INTRODUCTION

Discordance in hormone receptor status has been observed between two breast tumors of the same patients; however, the degree of heterogeneity is debatable with regard to whether it reflects true biological difference or the limited accuracy of receptor assays.

METHODS

A Bayesian misclassification correction method was applied to data on hormone receptor status of two primary breast cancers from the Surveillance, Epidemiology, and End Results database between 1990 and 2010 and to data on primary breast cancer and paired recurrent/metastatic disease assembled from a meta-analysis of the literature published between 1979 and 2014.

RESULTS

The sensitivity and specificity of the estrogen receptor (ER) assay were estimated to be 0.971 and 0.920, respectively. After correcting for misclassification, the discordance in ER between two primary breast cancers was estimated to be 1.2% for synchronous ipsilateral pairs, 5.0% for synchronous contralateral pairs, 14.6% for metachronous ipsilateral pairs, and 25.0% for metachronous contralateral pairs. Technical misclassification accounted for 53%-83% of the ER discordance between synchronous primary cancers and 11%-25% of the ER discordance between metachronous cancers. The corrected discordance in ER between primary tumors and recurrent or metastatic lesions was 12.4%, and there were more positive-to-negative changes (10.1%) than negative-to-positive changes (2.3%). Similar patterns were observed for progesterone receptor (PR), although the overall discordance in PR was higher.

CONCLUSION

A considerable proportion of discordance in hormone receptor status can be attributed to misclassification in receptor assessment, although the accuracy of receptor assays was excellent. Biopsy of recurrent tumors for receptor retesting should be conducted after considering feasibility, cost, and previous ER/PR status.

Predicting Breast Cancer Endocrine Responsiveness Using Molecular Imaging

The estrogen receptor (ER) is expressed on the vast majority of newly diagnosed breast cancers, yet not all ER-positive tumors will respond to endocrine therapy. Selecting patients for endocrine therapy can be considered as a series of predictive tests: does the tumor express the ER and if so, will the endocrine therapy interact with the target to produce a response? These are both challenges to which molecular imaging is functionally suited. Imaging of the ER has been most successful using 16-α[18F]-flouro-17β-estradiol (FES) positron emission tomography (PET). Functional imaging of the ER using FES-PET has been shown to be a predictive tool in determining response to endocrine therapy, and PET imaging of the ER can be used to measure the pharmacodynamic effect of ER-directed endocrine therapy. This article reviews the literature on FES-PET as a functional tool in predicting response to endocrine therapy in breast cancer and discusses future directions.

Variation in hormone receptor and HER-2 status between primary and metastatic breast cancer: review of the literature

IMPORTANCE OF THE FIELD

Hormone and human epidermal growth factor receptor 2 (HER-2) receptors are two important pharmaceutical targets that affect the survival of patients with metastatic breast cancer. Discordance of hormone and HER-2 receptors were reported in a series of studies. Receptor status was reported to change in both directions, yet alteration occurs mostly in the loss of positivity for both receptors. We do not know both the exact mechanism of this process or the contribution rate of technical mistakes; a number of mechanisms might be responsible. Factors suggested include: tumor heterogeneity, clonal selection of tumor cell subpopulations, genetic instability of tumor cells, local or systemic treatments, the time interval between primary tumor and metastasis, receptor status determination techniques, and the site of metastasis.

AREAS COVERED IN THIS REVIEW

Studies of estrogen, progesterone and HER-2 receptor discordance between primary and metastasis of breast cancer are summarized. Laboratory evaluation of estrogen, progesterone and HER-2 receptors, and possible causes of receptor discordance, are summarized. Literature data are reviewed; the major shortcoming of these studies is that they are mostly retrospective.

WHAT THE READER WILL GAIN

The reader will read a concise literature review about the studies on estrogen, progesterone and HER-2 receptor discordances between primary and metastasis of breast cancer.

TAKE HOME MESSAGE

We do not know whether the changes in receptor expression account for a true biological phenomenon or may result from inconsistent measurement. However, in light of current data, for the treatment plans that target the receptors, biopsy specimen from the metastatis of breast cancer must also be evaulated for alterations in the receptor status.

Prospective comparison of switches in biomarker status between primary and recurrent breast cancer: the Breast Recurrence In Tissues Study (BRITS)

Introduction

Immunohistochemistry of primary breast cancer is routinely used to guide changes in therapy at the time of relapse. Retrospective reviews suggest that the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor type 2 (HER2) receptor may differ between the primary and loco-regional recurrence or distant metastases. The Breast Recurrence In Tissues Study (BRITS) was a large, multicentre, prospective study to examine changes in ER, PR and HER2.

Methods

Matched primary and recurrent breast cancer tissue samples were prospectively collected from 205 women attending 20 institutions. Central laboratory immunohistochemical analysis of core biopsies and tissue microarrays of ER and PR using the Allred and Quickscore methods and HER2 (confirmed by fluorescence in situ hybridisation (FISH) for HER2 2+) were performed.

Results

From 205 consenting women, 18 (8.8%) did not have recurrent disease on biopsy, 35 were ineligible, 13 had insufficient paired tissue and 2 were excluded for safety reasons. Paired samples from 137 women, mean age 62.6 years (range 27-87 years), 83/137 (60.6%) postmenopausal with a median 92.2 months (range 5-327 months) from primary to recurrence and 88 (64.2%) as locoregional recurrence were successfully analysed. A switch in receptor status, in either direction, by Allred score, was identified for ER in 14 patients (10.2%; P = 0.983 Wilcoxon sign rank test), PR in 34 (24.8%; P = 0.003 Wilcoxon sign rank test) and HER2 in 4 (2.9%; P = 0.074 Wilcoxon sign rank test). There was no difference between locoregional or distant recurrence in the proportion who switched. The switch in receptor status led to a change in the subsequent treatment plan for 24 patients (17.5%).

Conclusions

This prospective study confirms retrospective evidence that the management of relapsed breast cancer should include confirmatory tissue sampling and identify switches of ER, PR or HER2 which change therapeutic management for one in six patients.

Estrogen and HER-2 receptor discordance between primary breast cancer and metastasis

Discordance in estrogen receptor and human epidermal growth factor receptor 2 receptor status between the primary tumor and recurrence is frequently reported in the literature. This is frequently interpreted as evidence for a change in the biology of breast cancer during the course of the disease. This commentary discusses some of the caveats of this interpretation. Discordant receptor results can be caused by any of 3 factors: (a) a genuine switch in the biology of the disease, (b) sampling error in focally receptor-positive cancers, and (c) limited accuracy and reproducibility of receptor assays. The relative contribution of each of these factors to discordant results is unknown. A switch in molecular class between primary and recurrent cancer (or residual cancer after therapy) appears to be a rare event based on the available limited molecular profiling data. Small pockets of strongly focally receptor-positive tumor nests in a larger receptor-negative cancer are also relatively infrequently seen. Discordance resulting from inherent limitations in assay reproducibility is evident from the frequently discordant receptor results even when the same samples are assessed in different laboratories (e.g., central versus local laboratory). A repeat tumor biopsy is clearly justified when it is suspected, on clinical grounds, that the original receptor results may have been false negative or when the diagnosis of metastatic disease is in question. However, routine repeat biopsy for receptor re-evaluation does not necessarily improve diagnostic accuracy and have a potential to harm through a false-negative result. For patients with clinical courses consistent with hormone responsiveness, or with prior positive hormone receptor results, a course of endocrine therapy is reasonable regardless of the most recent hormone receptor assay result.

Cytokeratin 5 positive cells represent a steroid receptor negative and therapy resistant subpopulation in luminal breast cancers

A majority of breast cancers are estrogen receptor (ER) positive and have a luminal epithelial phenotype. However, these ER⁺ tumors often contain heterogeneous subpopulations of ER⁻ tumor cells. We previously identified a population of cytokeratin 5 (CK5) positive cells within ER⁺ and progesterone receptor positive (PR⁺) tumors that is both ER⁻PR⁻ and CD44⁺, a marker of breast tumor-initiating cells (TICs). These CK5⁺ cells have properties of TICs in luminal tumor xenografts, and we speculated that they are more resistant to chemo- and anti-ER-targeted therapies than their ER⁺ neighbors. To test this, we used ER⁺PR⁺ T47D and MCF7 breast cancer cells. CK5⁺ cells had lower proliferative indices than CK5⁻ cells, were less sensitive to 5-fluorouracil and docetaxel, and cultures became enriched for CK5⁺ cells after treatments. CK5⁺ cells were less prone to drug-induced apoptosis than CK5⁻ cells. In cells treated with 17β-estradiol (E) plus anti-estrogens tamoxifen or fulvestrant, ER protein levels decreased, and CK5 protein levels increased, compared to controls treated with E alone. In ER⁺ tumors from patients treated with neoadjuvant endocrine therapies ER gene expression decreased, and CK5 gene expression increased in post compared to pre-treatment tumors. The number of CK5⁺ cells in tumors also increased in post- compared to pre-treatment tumors. We conclude that an ER⁻PR⁻CK5⁺ subpopulation found in many luminal tumors is resistant to standard endocrine and chemotherapies, relative to the majority ER⁺PR⁺CK5⁻ cells. Compounds that effectively target these cells are needed to improve outcome in luminal breast cancers.

Molecular imaging of breast cancer

Molecular imaging of breast cancer can potentially be used for breast cancer screening, staging, restaging, response evaluation and guiding therapies. Techniques for molecular breast cancer imaging include magnetic resonance imaging (MRI), optical imaging, and radionuclide imaging with positron emission tomography (PET) or single photon emission computed tomography (SPECT). This review focuses on PET and SPECT imaging which can provide sensitive serial non invasive information of tumor characteristics. Most clinical data are gathered on the visualization of general processes such as glucose metabolism with the PET-tracer [(18)F]fluorodeoxyglucose (FDG) and DNA synthesis with [18F]fluoro-L-thymidine (FLT). Increasingly more breast cancer specific targets are imaged such as the estrogen receptor (ER), growth factors and growth factor receptors. Imaging of the ER with the PET tracer 16-alpha-[(18)F]fluoro-17-beta-estradiol (FES) has shown a good correlation between FES tumor uptake and ER density. (111)In-trastuzumab SPECT to image the human epidermal growth factor receptor 2 (HER2) showed that in most patients with metastatic HER2 overexpressing disease more lesions were detected than with conventional staging procedures. The PET tracer (89)Zr-trastuzumab showed excellent, quantifiable, and specific tumor uptake. (111)In-bevacizumab for SPECT and (89)Zr-bevacizumab for PET-imaging have been developed for vascular endothelial growth factor (VEGF) imaging as an angiogenic marker. Lastly, tracers for the receptors EGFR, IGF-1R, PDGF-betaR and the ligand TGFbeta are under development. Although molecular imaging of breast cancer is still not commonly used in daily clinical practice, its application portfolio is expanding rapidly.

Comparative study of the immunohistochemical detection of hormone receptor status and HER-2 expression in primary and paired recurrent/metastatic lesions of patients with breast cancer

Recent studies have shown some degrees of discordance in ER, PR and HER-2 immunohistochemical expression between primary and recurrent/metastatic lesions (RML). Analysis was made on 78 patients with MBC whose ER, PR and/or HER-2 status were known both on the tissue samples of primary and RML. Among the RML sites, 29.5% were locoregional, 70.5% were distant metastatic sites. Among 75 patients with known ER expression on both primary and RML, 36% (n = 27) showed discordance on ER expression. Among 72 patients with known PR expression on both primary and RML, 54.2% (n = 39) showed discordance on PR expression. Among 61 patients with known HER-2 expression on both primary and RML, 14.7% (n = 9) showed discordance on HER-2 expression. No differences were observed when we compared patients who have discordant ER and HER-2 status with patients who have concordant results between the primary tumor and paired RML with respect to site of biopsy (locoregional vs distant metastasis) and prior therapies (chemotherapy and endocrine therapy). As these discordant results make changes in treatment decision, a biopsy of the metastatic lesion could be recommended in patients with MBC when feasible. Larger series are needed to identify the potential effect of prior therapies and site of metastasis on discordant results.

Tumor receptor imaging

Tumor receptors play an important role in carcinogenesis and tumor growth and have been some of the earliest targets for tumor-specific therapy, for example, the estrogen receptor in breast cancer. Knowledge of receptor expression is key for therapy directed at tumor receptors and traditionally has been obtained by assay of biopsy material. Tumor receptor imaging offers complementary information that includes evaluation of the entire tumor burden and characterization of the heterogeneity of tumor receptor expression. The nature of the ligand-receptor interaction poses a challenge for imaging--notably, the requirement for a low molecular concentration of the imaging probe to avoid saturating the receptor and increasing the background because of nonspecific uptake. For this reason, much of the work to date in tumor receptor imaging has been done with radionuclide probes. In this overview of tumor receptor imaging, aspects of receptor biochemistry and biology that underlie tumor receptor imaging are reviewed, with the estrogen-estrogen receptor system in breast cancer as an illustrative example. Examples of progress in radionuclide receptor imaging for 3 receptor systems--steroid receptors, somatostatin receptors, and growth factor receptors-are highlighted, and recent investigations of receptor imaging with other molecular imaging modalities are reviewed.

Comparison of HER-2 and hormone receptor expression in primary breast cancers and asynchronous paired metastases: impact on patient management

INTRODUCTION

The assessment of hormone receptors (HRs) and human epidermal growth factor receptor (HER)-2 is necessary to select patients who are candidates for hormonal and anti-HER-2 therapy. The evaluation of these parameters is generally carried out in primary tumors and it is not clear if reassessment in metastatic lesions might have an impact on patient management. The primary aim of this analysis was to compare HER-2 and HR status in primary tumors versus metastatic sites in breast cancer patients.

PATIENTS AND METHODS

Seventy-five patients with available samples from primary tumors and paired metastases were included. HER-2 status was evaluated by immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH); HR status was assessed by IHC.

RESULTS

Nineteen percent of primary tumors were HER-2 positive; 77% were HR positive. Sites of biopsied or resected metastases were: locoregional soft tissues (n = 30), liver (n = 20), central nervous system (n = 5), bone (n = 5), pleura (n = 4), distant soft tissues (n = 3), abdomen (stomach, colon, peritoneum) (n = 3), bronchus (n = 3), and bone marrow (n = 2). For paired metastases, the HER-2 status was unchanged in 84% of cases; two patients changed from positive to negative, while 10 patients converted from negative to positive (agreement, 84%; kappa = 0.5681). A change in HR status was observed in 16 cases (21%): nine cases from positive to negative and seven cases from negative to positive (agreement, 78.7%; kappa = 0.4158).

CONCLUSIONS

Further studies are necessary to better define the level of discordance in HER-2 or HR status between primary tumors and paired metastases. However, a biopsy of metastatic disease can be recommended, if feasible with minimal invasiveness, because treatment options might change for a significant proportion of patients.

18F-Fluoroestradiol

Estrogen receptor (ER) expression is an important determinant of breast cancer behavior and is critical for response to endocrine therapies such as tamoxifen and aromatase inhibitors. In current practice, ER expression is determined by assay of biopsy material. In more advanced disease, tissue assay may present practical difficulties and be associated with significant sampling error. This and other considerations motivated the development of ER imaging agents for positron emission tomography (PET), of which the most successful has been (18)F-16alpha-17beta-fluoroestradiol (FES). In this review, we highlight aspects of ER biology and the importance of the ER in breast cancer therapy; review the structure and synthesis of FES; describe its kinetics and safety/dosimetry data; and highlight validation studies. Also discussed are early results in patients using FES-PET to localize ER-expressing tumors and associated data pointing toward its accuracy as a predictive assay for breast cancer endocrine therapy. Finally, early data for tumors and sites other than breast cancer are mentioned. Preliminary data strongly point toward potential clinical utility for FES-PET, motivating further validation and future clinical trials with prospective endpoints tested under appropriate regulatory oversight.

Quantitative analysis of estrogen receptor heterogeneity in breast cancer

Immunohistochemical analyses (IHC) of biomarkers are extensively used for tumor characterization and as prognostic and predictive measures. The current standard of single slide analysis assumes that one 5 microM section is representative of the entire tumor. We used our automated image analysis technology (AQUA) using a modified IHC technique with fluorophores to compare estrogen receptor (ER) expression in multiple blocks/slides from cases of primary breast cancer with the objective of quantifying tumor heterogeneity within sections and between blocks. To normalize our ER scores and allow slide-to-slide comparisons, 0.6 microm histospots of representative breast cancer cases with known ER scores were assembled into a 'gold standard array' (GSA) and placed adjacently to each whole section. Overall, there was excellent correlation between AQUA scores and the pathologist's scores and reproducibility of GSA scores (mean linear regression R value 0.8903). Twenty-nine slides from 11 surgical cases were then analyzed totaling over 2000 AQUA images. Using standard binary assignments of AQUA (>10) and pathologist's (>10%) scores as being positive, there was fair concordancy between AQUA and pathologist scores (73%) and between slides from different blocks from the same cases (75%). However using continuous AQUA scores, agreement between AQUA and pathologist was far lower and between slides from different blocks from the same cases only 19%. Within individual slides there was also significant heterogeneity in a scattered pattern, most notably for slides with the highest AQUA scores. In sum, using a quantitative measure of ER expression, significant block-to-block heterogeneity was found in 81% of cases. These results most likely reflect both laboratory-based variability due to lack of standardization of immunohistochemistry and true biological heterogeneity. It is also likely to be dependent on the biomarker analyzed and suggests further studies should be carried out to determine how these findings may affect clinical decision-making processes.

Metastatic breast cancer: an updating

This article reports on recent advances on metastatic breast cancer. Detection, prognostic factors, predictors of response to therapy and therapy, with particular regard to targeted therapies, were examined.

DETECTION

Unlike current guidelines that yet do not routinely recommend intensive clinical-instrumental post-operative follow-up of breast cancer patients, relatively large data collected in the last decades have shown that an intensive post-operative follow-up with 'dynamic evaluation' of a suitable tumour marker panel precedes a few months as average the clinical and/or instrumental sign of a pending relapse in most relapsed patients and largely limits the use of the common instrumental examinations.

PROGNOSIS AND THERAPY PREDICTORS

Disease-free interval (DFI)<or=24 months, adjuvant chemotherapy, liver and distant soft tissue involvement or DFI>24 months and disease confined to bony skeleton are prognostic factors more often correlated with relatively poor or prolonged survival, respectively. Estrogen receptor (ER) expression in primary tumour and at the relapse correlates strongly with response to salvage hormone therapy and data from large trials showed that 38-59% of ER and/or PR+ post-menopausal patients had clinical benefit from first line tamoxifen or aromatase inhibitors. An inverse correlation of ER with epidermal growth factor receptor (EGFR) has been found. The co-expression of HER-2/neu and/or elevated serum HER-2/neu protein level were associated with a low rate and shorter duration of response of ER+ patients to first line hormone therapy. Accordingly, ER-EGFR- compared with ER-EGFR+ tumours are usually more responsive to endocrine therapy. High class III beta-tubulin expression or fall in insulin-like growth factor binding protein-3 (IGFBP-3) from baseline levels have been found to significantly predict resistance to chemotherapeutic agents.

THERAPY

Liposomes as carrier of doxorubicin (Caelix, Evacet, Myocet) is one approach to decrease the anthracycline-related cardiac toxicity. Weekly paclitaxel or docetaxel and oral formulation of vinorelbine and 5-fluorouracil (5-FU) (capecitabine) provide new effective and well tolerated options that reach greater dose intensity and cumulative dose than with the conventional schedules. As to the so called 'tailored' or targeted therapies, the more potent and highly selective third generation of aromatase inhibitors (letrozole, anastrozole, exemestane) targeting ER+ tumours by estrogen deprivation, challenge tamoxifen as current standard first line therapy in postmenopausals. One pilot study showed that stimulation of cellular immunity by the addition of beta-interferon-interleukin-2 sequence in patients on clinical benefit on first line tamoxifen significantly prolonged median overall survival (OS) and duration of response compared to that observed in similar patients only treated with tamoxifen. Trastuzumab, a humanised monoclonal antibody to extracellular domain of HER-2, plus conventional chemotherapy has become a standard of care for women with overexpressing HER-2 tumours. Bevacizumab is a recombinant humanised monoclonal antibody to vascular endothelial growth factor (VEGF) that in refractory metastatic breast cancer doubled the response rate of capecitabine although it did not affect survival. Finally, the so called 'oligometastatic' and a few stage IV diseases are conditions amenable to be rendered with no evidence of disease (NED) after local surgery and/or radiation. In both, as well as in complete responders to chemotherapy, minimal residual disease (m.r.d.) likely continues to be present. Recent data suggest that 'biological' therapy (immunomodulators and/or retinoids with or without hormone therapy), might be suitable to be successfully tested in these patients as maintenance treatment given soon after local intervention or chemotherapy.

Quantitative Fluoroestradiol Positron Emission Tomography Imaging Predicts Response to Endocrine Treatment in Breast Cancer

Purpose

In breast cancer, [18F]fluoroestradiol (FES) positron emission tomography (PET) correlates with estrogen receptors (ER) expression and predicts response to tamoxifen. We tested the ability of FES-PET imaging to predict response to salvage hormonal treatment in heavily pretreated metastatic breast cancer patients, predominantly treated with aromatase inhibitors.

Patients and Methods

Initial FES uptake measurements in 47 patients with ER-positive tumors were correlated with subsequent tumor response to 6 months of hormonal treatment. Most patients had bone dominant disease and prior tamoxifen exposure. Response was compared to initial FES-PET uptake, measured qualitatively and quantitatively using standardized uptake value (SUV) and estradiol-binding flux.

Results

Eleven of 47 patients (23%) had an objective response. While no patients with absent FES uptake had a response to treatment, the association between qualitative FES-PET results and response was not significant (P = .14). However, quantitative FES uptake and response were significantly associated; zero of 15 patients with initial SUV less than 1.5 responded to hormonal therapy, compared with 11 of 32 patients (34%) with SUV higher than 1.5 (P < .01). In the subset of patients whose tumors did not overexpress HER2/neu, 11 of 24 patients (46%) with SUV higher than 1.5 responded.

Conclusion

Quantitative FES-PET can predict response to hormonal therapy and may help guide treatment selection. Treatment selection using quantitative FES-PET in our patient series would have increased the rate of response from 23% to 34% overall, and from 29% to 46% in the subset of patients lacking HER2/neu overexpression. A multi-institutional collaborative trial would permit definitive assessment of the value of FES-PET for therapeutic decision making.

ERK1/2 inhibition increases antiestrogen treatment efficacy by interfering with hypoxia-induced downregulation of ERalpha: a combination therapy potentially targeting hypoxic and dormant tumor cells

Tumor hypoxia is associated with cancer invasiveness, metastasis and treatment failure. Recent data suggest that the major target for endocrine treatment in breast cancer, ERalpha, is downregulated during hypoxia, but the mechanism behind this remains unknown. MAPK signaling as well as ERalpha regulation has earlier been independently linked to hypoxia and we now demonstrate HIF-1alpha and ERK1/2-activation in vivo towards the necrotic zone in DCIS of the breast, parallel with ERalpha downregulation. Hypoxia further caused transcriptional downregulation of ERalpha via activation of ERK1/2 in cell lines and, importantly, MEK1/2 inhibitors (U0126 or PD184352) or ERK1/2 suppression by siRNA partially restored the ERalpha expression. U0126 combined with tamoxifen accordingly produced an increased efficacy of the anti-estrogens during hypoxia. Based on these findings, we suggest a promising novel therapy for ERalpha-positive breast cancer where a combination of endocrine treatment and ERK1/2 inhibitors may increase treatment response by improved targeting of dormant hypoxic tumor cells.

Reliance on hormone receptor assays of surgical specimens may compromise outcome in patients with breast cancer

PURPOSE

To assess the concordance of breast cancer immunohistochemical receptor assays on core biopsy and surgical specimens.

PATIENTS AND METHODS

We identified 100 patients whose core biopsy and definitive surgical specimens were processed in our hospital. New sections, with core and surgical specimens on the same slides, were stained for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2) immunohistochemistry (IHC). Two pathologists assessed the sections independently. Raw scores and clinically significant groupings were compared.

RESULTS

Concordance for ER, PR, overall hormone receptor (HR), and HER-2 status was seen in 86%, 83%, 90%, and 80% of patients, respectively. The core was positive, while the surgical specimen was negative in 13%, 11%, 9%, and 1% of patients, respectively. Using a log-linear model, differences in ER, PR, and HER-2 staining were all in the direction of stronger staining in the cores, and were statistically significant. Nine percent (95% CI, 4.2% to 16.4%) of women in this group would have had endocrine therapy inappropriately withheld if management decisions were based on surgical specimen results alone.

CONCLUSION

ER and PR assays on core biopsy specimens are more reliable than assays on surgical specimens. Receptor IHC should be performed on core biopsy specimens to avoid patients with HR positive cancers not receiving appropriate hormonal therapy and being overtreated with systemic chemotherapy. Biopsy should be considered in patients with "receptor negative" cancer and recurrent disease.

Estrogen receptor analysis for breast cancer: current issues and keys to increasing testing accuracy

The estrogen receptor (ER) is a regulator of cellular growth, proliferation, and differentiation. In addition to having prognostic value, ER is the most important biologic marker of therapeutic response in breast cancer. Some level of measurable ER protein is expressed in 70-80% of human breast. Immunohistochemistry is the current method of choice for ER assessment, and its predictive value has been shown to be superior to that of biochemically based assays. Although accurate ER protein assessment is critical for optimal treatment of patients with breast cancer, studies have demonstrated inter-laboratory variability in ER detection. False-negative results for tumors with low ER protein levels have been a subject of recent concern. Lack of standardization for immunohistochemistry between laboratories is thought to be the major reason for testing errors, although variability in scoring methods and reporting practices, which can affect results, also plays a role. In this article, we review studies addressing interlaboratory variability and recommend optimal testing techniques and reporting procedures for ER testing, with the goal of increasing interlaboratory standardization for ER analysis by immunohistochemistry. We additionally highlight recent biologic, molecular, and gene expression profiling data related to ER in breast cancer.

Hormonal therapy for breast cancer. An update

The use of endocrine manipulation for the treatment of breast cancer has been available for 100 years, but in recent years the number of therapeutic options available to patients has increased dramatically. This article considers new developments in the use of hormonal agents for the treatment and prevention of breast cancer.

Absence of progesterone receptor associated with secondary breast cancer in postmenopausal women

The relationship between expression of receptors for oestrogen and progesterone (ER and PR) and disease progression in breast cancer was investigated by comparing immunocytochemical determinations of ER and PR in fine needle aspirates from primary and secondary breast tumours. Rates of receptor expression were significantly higher in primary than in secondary lesions: for ER 63.3% (n = 689) compared with 45.3% (n = 223), and for PR 53.7% (n = 443) compared with 33.1% (n = 121). The effect of menopausal status was examined by subdividing the patient cohort into those over or under the age of 50 years. In both instances, ER expression in secondary tumours was relatively low; however, only postmenopausal patients had significantly lower rates of PR expression in secondary tumours. Consistent with this, an increase in the ER+PR- profile in secondary tumours compared with primary cases from postmenopausal patients was seen, and in a multivariate analysis, a specific absence of PR expression in secondary tumours was revealed. Comparison of ER and PR expression in simultaneously sampled primary tumours and lymph node metastases from the same patient showed that receptor expression was stable with progression to a metastatic site as results were concordant for ER in 92% (n = 88) and PR in 93.8% of cases (n = 65). These results suggest that absence of PR expression in primary breast cancer is associated with disease progression and may be a marker of an aggressive tumour phenotype.

Steroid receptors in pleural effusions of advanced breast cancer patients

The steroid receptor content in breast carcinoma correlates with the responsiveness of malignant cells to endocrine manipulation. Although the steroid receptor status of the primary tumor is mostly used to select systemic therapy, it was suggested that steroid receptor content should be evaluated in metastatic lesions whenever possible. In this study the estrogen and progesterone receptor content was determined biochemically in 38 pleural effusions from advanced breast cancer patients. In 17/38 patients the steroid receptor status was assessed twice during the course of the disease - at diagnosis in the primary tumor/lymph nodes, and subsequently in metastatic pleural effusion fluid. A trend towards lower receptor values in pleural fluids was evident. There was no correlation between pleural steroid receptor content and pleural response to endocrine or chemo/endocrine therapy, indicating that the usefulness of effusional steroid receptors for therapy planning of advanced breast cancer could not be confirmed in this study.

Estrogen and progesterone receptor content in bilateral breast cancer

Estrogen and progesterone receptor content was determined in 34 patients with synchronous and 23 patients with asynchronous bilateral breast cancer. Steroid receptor content was measured quantitatively by DCC method. It was shown that progesterone receptor content could not be predicted, as well as, that steroid receptor content of the second tumor significantly influenced the development of asynchronous bilateral breast cancer. The high discordance rate concerning histologic type between two tumors within synchronous as well as asynchronous biopsies was observed. The obtained results indicate that both synchronous and asynchronous bilateral breast tumors may be considered as biologically different tumors whose both steroid receptor levels should be determined whenever possible.