Recent advances in endocrine therapy for postmenopausal women with early breast cancer: implications for treatment and prevention

NFκB affects estrogen receptor expression and activity in breast cancer through multiple mechanisms

Estrogen receptor (ER) and NFκB are two widely expressed, pleiotropic transcription factors that have been shown to interact and affect one another's activity. While the ability of ER to repress NFκB activity has been extensively studied and is thought to underlie the anti-inflammatory activity of estrogens, how NFκB signaling affects ER activity is less clear. This is a particularly important question in breast cancer since activation of NFκB in ER positive tumors is associated with failure of endocrine and chemotherapies. In this review, we provide an update on the multiple mechanisms by which NFκB can influence ER activity, including down-regulation of ER expression, enhanced ER recruitment to DNA, and increased transcriptional activity of both liganded and unliganded ER. Additionally, a novel example of NFκB potentiation of ER-dependent gene repression is reviewed. Together, these mechanisms can alter response to endocrine therapies and may underlie the poor outcome for women with ER positive tumors that have active NFκB signaling.

Use of aromatase inhibitors and bisphosphonates as an anticancer therapy in postmenopausal breast cancer

Breast cancer is a major cause of morbidity and mortality in postmenopausal women worldwide. Reducing the risk of distant disease recurrence is a primary goal of adjuvant endocrine therapy. As we await data from ongoing Phase III comparison trials, an emerging body of evidence demonstrates important differences between third-generation aromatase inhibitors, particularly with respect to potency and prevention of early distant metastases. Furthermore, a growing body of evidence demonstrates anticancer benefits of bisphosphonates in adjuvant breast cancer and other settings. This article outlines the proceedings from an Expert Panel meeting of regionally diverse breast cancer specialists regarding the appropriate use of aromatase inhibitors in postmenopausal hormone-responsive early breast cancer and bisphosphonates as anticancer therapy in adjuvant breast cancer.

Activity of Fulvestrant 500 mg Versus Anastrozole 1 mg As First-Line Treatment for Advanced Breast Cancer: Results From the FIRST Study

Purpose

To compare the clinical activity of the pure antiestrogen fulvestrant at 500 mg/mo (double the approved dose) with the aromatase inhibitor anastrozole as first-line endocrine therapy for advanced hormone receptor–positive breast cancer in postmenopausal women.

Patients and Methods

FIRST (Fulvestrant First-Line Study Comparing Endocrine Treatments) is a phase II, randomized, open-label, multicenter study of a fulvestrant high-dose (HD) regimen (500 mg/mo plus 500 mg on day 14 of month 1) versus anastrozole (1 mg/d). The primary efficacy end point was clinical benefit rate (CBR), defined as the proportion of patients experiencing an objective response (OR) or stable disease for ≥ 24 weeks. The primary analysis was performed 6 months after the last patient was randomly assigned.

Results

CBR was similar for fulvestrant HD (n = 102) and anastrozole (n = 103), 72.5% v 67.0%, respectively (odds ratio, 1.30; 95% CI, 0.72 to 2.38; P = .386). Objective response rate (ORR) was also similar between treatments: fulvestrant HD, 36.0%; anastrozole, 35.5%. Time to progression (TTP) was significantly longer for fulvestrant versus anastrozole (median TTP not reached for fulvestrant HD v 12.5 months for anastrozole; hazard ratio, 0.63; 95% CI, 0.39 to 1.00; P = .0496). Duration of OR and CB also numerically favored fulvestrant HD. Both treatments were well tolerated, with no significant differences in the incidence of prespecified adverse events.

Conclusion

First-line fulvestrant HD was at least as effective as anastrozole for CBR and ORR and was associated with significantly longer TTP. Fulvestrant HD was generally well tolerated, with a safety profile similar to that of anastrozole.

Economic evaluation of fulvestrant as an extra step in the treatment sequence for ER-positive advanced breast cancer

Drug therapies for advanced breast cancer in hormone-receptor-positive disease include both hormonal and chemotherapies. Current UK practice is to minimise toxicity by using sequential hormonal agents for as long as clinically appropriate. A Markov model was developed to investigate the cost effectiveness of different sequences of therapies, particularly exploring the effects of adding an additional hormonal agent, fulvestrant, to the treatment pathway. A systematic review was undertaken and a panel of seven UK oncologists validated assumptions used for treatment efficacy, treatment pathways and resources used. Fulvestrant was found to be a cost-effective treatment option when added to the treatment sequence as a second- or third-line hormonal therapy for advanced disease. For a cohort of 1000 patients, fulvestrant as a second-line hormone therapy provided an additional 47 life years and 41 quality-adjusted life years (QALYs), at an additional cost of pound 301 359. This equated to pound 6500 per life years gained and pound 7500 per QALY. When used as a third-line option, the fulvestrant arm was dominant providing an increase in health benefit of 27 QALYs for the whole cohort, at a mean overall cost reduction of pound 430 per patient. Sensitivity analyses showed these results to be robust, demonstrating that fulvestrant is an economically viable additional endocrine option in the United Kingdom for the treatment of hormone responsive advanced breast cancer.

Aromatase Inhibitors and Musculoskeletal Pain in Patients With Breast Cancer

Aromatase inhibitors are recommended for use by postmenopausal women who have estrogen receptor-positive early-stage breast cancer. They reduce local and distant recurrence more effectively than tamoxifen. Anastrozole (Arimidex, AstraZeneca Pharmaceuticals LP), letrozole (Femara, Novartis Pharmaceuticals Corporation), and exemestane (Aromasin, Pfizer Inc.) inhibit aromatase activity, thus significantly decreasing estrogen production in tissues such as liver, muscle, and fat. Very low levels of estrogen may be one cause of musculoskeletal pain, a common side effect associated with the drugs. In the major adjuvant aromatase inhibitor clinical trials, 25%-30% of the patients enrolled experienced musculoskeletal pain. Although quality-of-life studies demonstrate that aromatase inhibitors are well tolerated overall, some women discontinue this treatment because of musculoskeletal pain. Little is known about how to predict, measure, or manage musculoskeletal pain caused by aromatase inhibition. Oncology nurses play an important role in the assessment and management of side effects related to cancer. This article provides an overview of the current knowledge about musculoskeletal pain in patients with breast cancer receiving aromatase inhibitor therapy.

Hormonal breast cancer agents: implications for the primary care provider

PURPOSE

Over 2 million breast cancer survivors are in the United States, making women with breast cancer the largest group of cancer survivors. The purpose of this article is to review the current knowledge regarding survivorship issues in women with early-stage, estrogen receptor-positive breast cancer, focusing on advances in hormonal therapies for reducing risk of recurrence.

DATA SOURCES

Published research studies, clinical treatment guidelines, and ongoing clinical trials.

CONCLUSIONS

Innovations in antiestrogenic and estrogen modulator therapies are an important aspect of ongoing care after primary breast cancer treatment. Primary care providers may play an important role in monitoring potential complications of antiestrogenic treatment.

IMPLICATIONS FOR PRACTICE

This article reviews the current state of the science in hormonal breast cancer agents for breast cancer survivors. With the high incidence and prevalence of breast cancer, primary care providers need to be aware of the potential short- and long-term health risks and benefits of hormonal therapies for breast cancer survivors.

Small optic cup sizes among women using tamoxifen: assessment with scanning laser ophthalmoscopy

PURPOSE

There is a substantial literature showing that the selective estrogen receptor modulator tamoxifen can block swelling-activated chloride channels, such as those in astrocytes. This study aimed to test the hypothesis that anatomic characteristics consistent with swelling may be measured within the optic nerve head (ONH) of tamoxifen users whose ONH appearance is considered within normal limits.

METHODS

Indices of ONH topography were measured using the Heidelberg Retina Tomograph II (HRT) for two populations of women ages 40-69 years: (1) subjects using tamoxifen (20 mg/day) as adjuvant therapy after successful primary treatment for breast cancer and (2) control subjects not using any hormonal medication. All subjects had excellent visual acuity (with 20/20 or better in the test eye), and all appeared to be free of eye disease, as based on conventional photographic assessment. The study design was cross-sectional. The various ONH indices were assessed as functions of the duration of tamoxifen use.

RESULTS

The optic cups of short-term tamoxifen users (<or=2 years) were significantly smaller in both the lateral and axial directions than the optic cups of the control subjects. Of the 27 short-term users, 23 had cup volumes smaller than the median value for the control subjects. The cup sizes of long-term users (> 2 years, <or=5 years) were not distinguishable from those of the control subjects. The presence of small cups among short-term users did not depend on subjects' medical histories prior to tamoxifen use. Disk margin indices were not related significantly to the duration of tamoxifen use.

CONCLUSIONS

Small cup sizes consistent with localized subclinical swelling are not rare among short-term tamoxifen users. Thus, small cups are not likely to be a manifestation of a cumulative-dose toxicity. Instead, they probably result from other causes, possibly involving the action of tamoxifen on estrogen receptors. Further investigation with longitudinal and interventional methodologies is needed to definitively interpret the results.

An estrogen receptor-negative breast cancer subset characterized by a hormonally regulated transcriptional program and response to androgen

Little is known of the underlying biology of estrogen receptor-negative, progesterone receptor-negative (ER(-)/PR(-)) breast cancer (BC), and few targeted therapies are available. Clinical heterogeneity of ER(-)/PR(-) tumors suggests that molecular subsets exist. We performed genome-wide expression analysis of 99 primary BC samples and eight BC cell lines in an effort to reveal distinct subsets, provide insight into their biology and potentially identify new therapeutic targets. We identified a subset of ER(-)/PR(-) tumors with paradoxical expression of genes known to be either direct targets of ER, responsive to estrogen, or typically expressed in ER(+) BC. Differentially expressed genes included SPDEF, FOXA1, XBP1, CYB5, TFF3, NAT1, APOD, ALCAM and AR (P<0.001). A classification model based on the expression signature of this tumor class identified molecularly similar BCs in an independent human BC data set and among BC cell lines (MDA-MB-453). This cell line demonstrated a proliferative response to androgen in an androgen receptor-dependent and ER-independent manner. In addition, the androgen-induced transcriptional program of MDA-MB-453 significantly overlapped the molecular signature of the unique ER(-)/PR(-) subclass of human tumors. This subset of BCs, characterized by a hormonally regulated transcriptional program and response to androgen, suggests the potential for therapeutic strategies targeting the androgen signaling pathway.

Understanding breast cancer risk -- where do we stand in 2005?

Breast cancer is the most frequent cancer in women and represents the second leading cause of cancer death among women (after lung cancer). The etiology of breast cancer is still poorly understood with known breast cancer risk factors explaining only a small proportion of cases. Risk factors that modulate the development of breast cancer discussed in this review include: age, geographic location (country of origin) and socioeconomic status, reproductive events, exogenous hormones, lifestyle risk factors (alcohol, diet, obesity and physical activity), familial history of breast cancer, mammographic density, history of benign breast disease, ionizing radiation, bone density, height, IGF- 1 and prolactin levels, chemopreventive agents. Additionally, we summarized breast cancer risk associated with the following genetic factors: breast cancer susceptibility high-penetrance genes (BRCA1, BRCA2, p53, PTEN, ATM, NBS1 or LKB1) and low-penetrance genes such as cytochrome P450 genes (CYP1A1, CYP2D6, CYP19), glutathione S-transferase family (GSTM1, GSTP1), alcohol and one-carbon metabolism genes (ADH1C and MTHFR), DNA repair genes (XRCC1, XRCC3, ERCC4/XPF) and genes encoding cell signaling molecules (PR, ER, TNFalpha or HSP70). All these factors contribute to a better understanding of breast cancer risk. Nonetheless, in order to evaluate more accurately the overall risk of breast tumorigenesis, novel genetic and phenotypic traits need to be identified.

Estrogen synthesis in the central nucleus of the amygdala following middle cerebral artery occlusion: Role in modulating neurotransmission

Stroke-induced lesions of the insular cortex in the brain have been linked to autonomic dysfunction (sympathoexcitation) leading to arrhythmogenesis and sudden cardiac death. In experimental models, systemic estrogen administration in male rats has been shown to reduce stroke-induced cell death in the insular cortex as well as prevent sympathoexcitation. The central nucleus of the amygdala has been postulated to mediate sympathoexcitatory output from the insular cortex. We therefore set out to determine if endogenous estrogen levels within the central nucleus of the amygdala are altered following stroke and if microinjection of estrogen into the central nucleus of the amygdala modulates autonomic tone. Plasma estrogen concentrations were not altered by middle cerebral artery occlusion (22.86+/-0.14 pg/ml vs. 21.24+/-0.33 pg/ml; P>0.05). In contrast, estrogen concentrations in the central nucleus of the amygdala increased significantly following middle cerebral artery occlusion (from 20.83+/-0.54 pg/ml to 76.67+/-1.59 pg/ml; P<0.05). Local infusion of an aromatase inhibitor, letrozole, into the central nucleus of the amygdala at the time of middle cerebral artery occlusion prevented the increase in estrogen concentration suggesting that this increase was dependent on aromatization from testosterone. Furthermore, bilateral microinjection of estrogen (0.5 microM in 200 nl) directly into the central nucleus of the amygdala significantly decreased arterial pressure and sympathetic tone and increased baroreflex sensitivity, and these effects were enhanced following co-injection with either an N-methyl-D-aspartate or non-N-methyl-D-aspartate receptor antagonist. Taken together, the results suggest that middle cerebral artery occlusion resulted in synthesis of estrogen within the central nucleus of the amygdala and that this enhanced estrogen level may act to attenuate overstimulation of central nucleus of the amygdala neurons to prevent middle cerebral artery occlusion-induced autonomic dysfunction.

Preferences of Women Evaluating Risks of Tamoxifen (POWER) study of preferences for tamoxifen for breast cancer risk reduction

BACKGROUND

The objective of this study was to understand the attitudes and preferences of risk-eligible women regarding use of tamoxifen for breast cancer risk reduction.

METHODS

A cross-sectional, mixed-methods interview study was conducted at a university medical center and at community sites. Participants were women who had an estimated 5-year breast cancer risk > or = 1.7% and no prior breast cancer. Interviews were conducted in English or Spanish. The interview included a 15-minute, standardized educational session on the potential benefits and harms of tamoxifen followed by close-ended and open-ended questions about participants' inclinations to take tamoxifen and factors important to their decision. A demographic questionnaire, a test on knowledge of potential benefits and harms of tamoxifen, and an interview evaluation were included.

RESULTS

Two hundred fifty-five women completed interviews. Their estimated mean 5-year breast cancer risk was 2.8%; and their mean self-perceived 5-year risk was 32.7%. After the educational intervention, 45 women (17.6%) were inclined to take tamoxifen. Very high risk women (> 3.5%) were no more inclined to take it than women with lower risk (1.7-3.5%). In a multivariable analysis, lower income, confidence in the effectiveness of tamoxifen, and concern about fractures were associated with being inclined to take it; concern about pulmonary embolism, dyspareunia, cataracts, and low self-perceived breast cancer risk were associated negatively with taking tamoxifen. Participants expressed concerns about adverse effects.

CONCLUSIONS

Less than 20% of women were interested in tamoxifen after education about potential benefits and harms, despite a very high self-perceived breast cancer risk. Candidate chemoprevention agents must have few potential adverse effects to achieve widespread acceptance.