Letrozole, a new oral aromatase inhibitor for advanced breast cancer: double-blind randomized trial showing a dose effect and improved efficacy and tolerability compared with megestrol acetate

A randomized, double-blind, controlled study of exemestane versus anastrozole for the first-line treatment of postmenopausal Japanese women with hormone-receptor-positive advanced breast cancer

The aromatase inhibitors exemestane and anastrozole are approved in Japan for first-line treatment of postmenopausal patients with advanced, hormone-receptor-positive breast cancer. This phase 3, randomized, double-blind study directly compared time to progression (TTP) for exemestane and anastrozole therapy in this patient population. Eligible patients were randomized to receive exemestane 25 mg or anastrozole 1 mg, each once daily. The primary endpoint was TTP based on assessment by an expert radiologic images review committee (ERIRC). Secondary endpoints included investigator-assessed TTP, time to treatment failure, overall survival, objective response rate, clinical benefit rate, and safety. A total 298 patients were randomized to receive exemestane (n = 149; mean age 63.4 years) or anastrozole (n = 149; mean age 64.0 years). Median ERIRC-assessed TTP was 13.8 and 11.1 months (hazard ratio = 1.007; 95 % confidence interval [CI]: 0.771, 1.317) and median investigator-assessed TTP was 13.8 and 13.7 months (hazard ratio = 1.059; 95 % CI: 0.816, 1.374) in the exemestane and anastrozole arms, respectively. Median overall survival was 60.1 months in the anastrozole arm and was not reached in the exemestane arm at data cutoff. The objective response rate was 43.9 % (95 % CI: 35.3, 52.8) and 39.1 % (95 % CI: 30.6, 48.1) in the exemestane and anastrozole arms, respectively. Treatment-related adverse events grade ≥3 occurred in 9.4 and 6.0 % of patients, and treatment-related serious adverse events occurred in 4.0 and 3.4 % of patients in the exemestane and anastrozole arms, respectively. In this study, the efficacy and safety profiles of exemestane were similar to those of anastrozole in Japanese patients with advanced, hormone-receptor-positive breast cancer; however, TTP non-inferiority of exemestane versus anastrozole was not confirmed.

Phase II study assessing lapatinib added to letrozole in patients with progressive disease under aromatase inhibitor in metastatic breast cancer-Study BES 06

This trial evaluated the effect of adding lapatinib to letrozole after clinical resistance to aromatase inhibitor (IA) treatment in hormone receptor-positive metastatic breast cancer. Postmenopausal women received daily letrozole plus lapatinib (1,500 mg). The primary end point was objective rate response (ORR) at week 12. Secondary objectives included time to response, duration of response, clinical benefit (CB), progression-free survival (PFS), overall survival, and safety. Twenty-four human epidermal growth factor receptor 2 (HER2)-negative patients were included with secondary resistance to IA. ORR at 12 weeks was 4 % (95 % confidence interval (CI), 0.7-20). Stable and progression diseases were reported in 25 % (95 % CI, 12-45) and 71 % (95 % CI, 51-85) of cases, respectively. At 24 weeks, the ORR increased to 8 %. CB was 21 % (95 % CI, 9-40). At a median follow-up of 27 months, median PFS was 3.4 months (95 % CI, 2.8-5.4). Grade 3 or 4 adverse events were rarely reported. No clinical cardiac toxicity was observed. Lapatinib was discontinued in two patients due to severe diarrhea. This trial was prematurely closed due to low recruitment. These preliminary results suggest that the addition of lapatinib to letrozole has a favorable safety profile and could overcome tumoral resistance to letrozole among HER2-negative tumors.

Progression-free survival with fulvestrant 500 mg and alternative endocrine therapies as second-line treatment for advanced breast cancer: a network meta-analysis with parametric survival models

BACKGROUND

Ouwens et al. and Jansen have presented methods for (network) meta-analysis of survival data by using a multidimensional treatment effect as an alternative to the synthesis of constant hazards ratios, which allow for a better fit to the data and the expected survival of competing interventions for cost-effectiveness analysis. However, results may be sensitive to the assumed underlying survival function.

OBJECTIVE

To estimate the expected progression-free survival (PFS) for fulvestrant 500 mg versus alternative hormonal therapies for postmenopausal women with advanced breast cancer who relapsed previously by means of a network meta-analysis of currently available randomized controlled trials using alternative underlying survival functions.

METHODS

Eleven randomized controlled trials were included that evaluated fulvestrant 500 mg (n = 3), fulvestrant 250 mg (n = 5), fulvestrant 250 mg loading dose (n = 3), anastrozole 1 mg (n = 3), megestrol acetate (n = 4), letrozole 2.5 mg (n = 3), letrozole 0.5 mg (n = 3), and exemestane (n = 2). PFS percentages and numbers at risk were derived from Kaplan-Meier curves and combined by means of Bayesian network meta-analysis on the basis of the difference in the shape and scale parameters of the Weibull, log-normal, and log-logistic parametric survival functions.

RESULTS

The log-normal distribution provided the best fit, suggesting that the proportional hazard assumption was not valid. Based on the difference in expected PFS, it was found that fulvestrant 500 mg is more efficacious than fulvestrant 250 mg, megestrol acetate, and anastrozole (-5.73 months; 95% credible interval [CrI]-10.67,-1.67). Expected PFS for fulvestrant 500 mg ranged from 10.87 (95% CrI 9.21, 13.07) to 17.02 (95% CrI 13.33, 22.02) months for the Weibull versus log-logistic distribution.

CONCLUSIONS

Fulvestrant 500 mg is expected to be more efficacious than fulvestrant 250 mg, megestrol acetate, and anastrozole 1 mg and at least as efficacious as exemestane and letrozole 2.5 mg in terms of PFS among postmenopausal women with advanced breast cancer after failure on endocrine therapy. The findings were not sensitive to the distribution, although the expected PFS varied substantially, emphasizing the importance of performing sensitivity analyses.

Population and target considerations for triple-negative breast cancer clinical trials

Triple-negative breast cancer (TNBC) is an aggressive disease subtype that has a poor prognosis. Extensive epidemiological evidence demonstrates clear socioeconomic and demographic associations with increased likelihood of TNBC in both poorer and minority populations. Thus, biological aggressiveness with few known therapeutic directions generates disparities in breast cancer outcomes for vulnerable populations. Emerging molecular evidence of potential targets in triple-negative subpopulations offers great potential for future clinical trial directions. However, trials must appropriately consider populations at risk for aggressive subtypes of disease in order to address this disparity most completely. New US FDA draft guidance documents provide both flexible outcomes for accelerated approvals as well as flexibility in design with adaptive trials. Careful planning with design, potential patient population and choices of molecular targets informed by biomarkers will be critical to address TNBC clinical care.

Current status and future perspectives in the endocrine treatment of postmenopausal, hormone receptor-positive metastatic breast cancer

INTRODUCTION

Endocrine therapy is a fundamental component of the therapeutic repertoire for treatment of metastatic, hormone receptor-positive breast cancer. Inevitably, however, tumors develop resistance to these compounds, and overcoming this phenomenon is a key motivator of research in this field.

AREAS COVERED

This review summarizes the current status of endocrine therapy for the treatment of metastatic disease, with a main focus on postmenopausal patients. Furthermore, strategies that could potentially sustain endocrine resistance and future perspectives in this direction are also to be described. Relevant references were identified by PubMed searches and from the abstract books of the annual meetings of The European Society of Clinical Oncology (ESMO), The American Society of Clinical Oncology (ASCO) and from the San Antonio Breast Cancer Symposia.

EXPERT OPINION

Combinations of endocrine therapy with HER2 targeting agents, as well as with compounds that can interfere with PI3K/Akt/mTOR signaling, are two promising strategies for delaying or overcoming endocrine resistance, mediated by these relevant biological pathways. Due to increased costs and the burden of toxicity associated with these combination therapies, compared to endocrine therapy alone, it is imperative to concentrate efforts on establishing biomarkers that can predict efficacy.

Aromatase inhibitors in the treatment of elderly women with metastatic breast cancer

The proportion of elderly women in the population is rising, and in tandem, the incidence of breast cancer rises with age. Because of health and tolerability concerns, as well as life expectancy, physicians may be reluctant to advise a standard treatment regimen for elderly patients with metastatic breast cancer. To elucidate this issue, we performed a literature review of clinical studies that included women with metastatic breast cancer who were over the age of 65. Our results show that although little clinical evidence exists, what is available suggests that standard treatment is tolerated and beneficial for patients meeting certain criteria. A geriatric assessment may identify specific patient groups (independent, dependent, or frail) and thereby guide treatment. Treatment recommendations for elderly patients with metastatic breast cancer are sparse, although first-line endocrine treatment, usually aromatase inhibitors or tamoxifen, is recommended for hormone-sensitive disease. In general, the evidence from clinical studies suggests that aromatase inhibitors are more effective than either tamoxifen or megestrol acetate as first- or second-line treatment in postmenopausal women with metastatic breast cancer. Ultimately, quality of life, treatment effects, and comorbidities are important aspects in this population and may guide treatment choice. To provide evidence-based treatment guidance, future clinical trials should include more patients over the age of 65 years.

Treatment algorithms for hormone receptor-positive advanced breast cancer: applying the results from recent clinical trials into daily practice—insights, limitations, and moving forward

Hormone receptor-positive (HR+) breast cancer is the most prevalent subtype of breast cancer in both early- and advanced-stage disease. Thus, the treatment of HR+ breast cancer has had the greatest global influence in improving clinical outcomes overall. Although the first-line metastatic breast cancer (MBC) trials comparing a third-generation aromatase inhibitor (AI) to tamoxifen have favored the AI, one of the challenges in translating these findings into clinical practice stems from the influence of prior adjuvant endocrine therapy, particularly the increasing use of adjuvant AIs today, on the choice of endocrine agent in the advanced setting because of the development of acquired resistance. Because the majority of patients enrolled into these studies were either endocrine-treatment naïve or exposed to tamoxifen only, the "real-life" applicability of the evidence is unclear. Because a superior dose of the selective estrogen receptor (ER) downregulator fulvestrant has now been established, its role as first-line therapy is being re-established. We are now starting to see the promise realized with blocking cross-talking growth factor pathways in addition to the ER pathway. The greatest efficacy is seen with the mammalian target of rapamycin (mTOR) inhibitor everolimus in combination with exemestane and, perhaps to a lesser extent, anti-HER2-directed therapy in combination with an AI. Future gains will likely involve a greater understanding of the redundancy and compensation induced by blocking these pathways, trials involving blocking multiple pathways in addition to hormonal agents, and the molecular interrogation of the individual's tumor in search of predictive biomarkers and "actionable" genomic aberrations.

Letrozole increases ovarian growth and Cyp17a1 gene expression in the rat ovary

OBJECTIVE

To evaluate the effects of letrozole on ovarian size and steroidogenesis in vivo, as well as on proliferation and steroidogenesis of theca-interstitial cells alone and in coculture with granulosa cells using an in vitro model.

DESIGN

In vivo and in vitro studies.

SETTING

Research laboratory.

ANIMAL(S)

Immature Sprague-Dawley female rats.

INTERVENTION(S)

In vivo effects of letrozole were studied in intact rats receiving either letrozole (90-day continuous-release SC pellets, 400 μg/d) or placebo pellets (control group). In in vitro experiments, theca cells were cultured alone or in coculture with granulosa cells in the absence or presence of letrozole.

MAIN OUTCOME MEASURE(S)

Deoxyribonucleic acid synthesis was determined by thymidine incorporation assay; steroidogenesis by mass spectrometry; and steroidogenic enzyme messenger RNA (mRNA) expression by polymerase chain reaction.

RESULT(S)

In vivo, letrozole induced an increase in ovarian size compared with the control group and also induced a profound increase of androgen, LH levels, and Cyp17a1 mRNA expression. Conversely, a decrease in Star, Cyp11a1, and Hsd3b1 transcripts was observed in letrozole-exposed rats. In vitro, letrozole did not alter either theca cell proliferation or Cyp17a1 mRNA expression. Similarly, letrozole did not affect Cyp17a1 transcripts in granulosa-theca cocultures.

CONCLUSION(S)

These findings suggest that letrozole exerts potent, but indirect, effect on growth of rat ovary and dramatically increases androgen levels and Cyp17a1 mRNA expression, the key enzyme regulating the androgen biosynthesis pathway. The present findings reveal novel mechanisms of action of letrozole in the rat ovary.

Letrozole: advancing hormone therapy in breast cancer

Letrozole is a type 2 aromatase inhibitor, which reduces availability of estrogen in postmenopausal women, thereby decreasing its ability to stimulate breast cancer cells. Phase III trials in both the advanced and early breast cancer setting have shown an improvement in disease-free survival compared with other compounds, including tamoxifen. Letrozole is well-tolerated, with the main adverse effects reported as hot flushes, arthritis, arthralgia and myalgia, and a trend towards increased risk of fracture.

The development of endocrine therapy for women with breast cancer

The development of endocrine therapies has transformed the treatment of patients with breast cancer. The shift from ablative surgery and aggressive chemotherapies to more targeted, better tolerated therapy has improved both mortality and quality of life for patients with hormone-responsive disease. During the 1970s, the selective oestrogen-receptor modulator, tamoxifen, emerged as a new treatment for women with advanced breast cancer. The subsequent development of numerous and diverse selective endocrine therapies such as luteinising hormone-releasing hormone agonists, aromatase inhibitors and oestrogen-receptor antagonists have added further treatment options. Furthermore, with well-tolerated and effective endocrine therapy, adjuvant treatment became an option for patients with early breast cancer. Tamoxifen emerged as the gold standard adjuvant therapy in the 1980s; however, later trials in postmenopausal women showed the aromatase inhibitors offer advantages over tamoxifen. In addition to AIs being indicated as adjuvant therapy, some are also being evaluated for use as a preventative measure in high-risk women. This chronological account outlines key milestones in the evolution of endocrine therapies over the last 40 years, highlighting each class of agent and the key trials that have led to changes in clinical practice. The advances in endocrine therapies outlined here, coupled with advances in breast cancer management and diagnostics, will likely lead to more patient-tailored therapy, resulting in greater clinical benefits and more cost-effective treatment strategies.

The sequential use of endocrine treatment for advanced breast cancer: where are we?

BACKGROUND

Hormone receptor-positive advanced breast cancer is an increasing health burden. Although endocrine therapies are recognised as the most beneficial treatments for patients with hormone receptor-positive advanced breast cancer, the optimal sequence of these agents is currently undetermined.

METHODS

We reviewed the available data on randomised controlled trials (RCTs) of endocrine therapies in this treatment setting with particular focus on RCTs reported over the last 15 years that were designed based on power calculations on primary end points.

RESULTS

In this paper, data are reviewed in postmenopausal patients for the use of tamoxifen, aromatase inhibitors and fulvestrant. We also consider the available data on endocrine crossover studies and endocrine therapy in combination with chemotherapy or growth factor therapies. Treatment options for premenopausal patients and those with estrogen receptor-/human epidermal growth factor receptor 2-positive tumours are also evaluated.

CONCLUSION

We present the level of evidence available for each endocrine agent based on its efficacy in advanced breast cancer and a diagram of possible treatment pathways.

Aromatase inhibitors in the treatment of breast cancer in post-menopausal female patients: an update

Estrogen and its metabolites play a significant role in the proliferation of hormone receptor-positive breast cancer. In postmenopausal women, aromatase inhibitors can significantly reduce estrogen levels by blocking enzyme-mediated estrogen synthesis within tissues. Third-generation aromatase inhibitors have now surpassed tamoxifen as first-line therapy for postmenopausal women with metastatic, hormone receptor-positive, breast cancer, showing improved response rates and time to progression. Aromatase inhibitors have shown incremental improvements in disease-free survival, lower local recurrence rates, lower metastatic recurrence rates, and a lower incidence of contralateral breast cancer over tamoxifen when used in the adjuvant setting. Aromatase inhibitors are recommended to be used as adjuvant therapy within the first 5 years of hormonal therapy and may be used either upfront for 5 years or sequenced with tamoxifen. No superiority of one aromatase inhibitor over another has yet been shown. The side effect profiles of aromatase inhibitors have some key differences compared with tamoxifen. These differences may influence treatment choices as well as impact compliance.

Management of patients with metastatic breast cancer

Hormone treatment is one of the key strategies in the management of metastatic breast cancer. Hormone treatment is one of the key strategies in the management of metastatic breast cancer. Aromatase inhibitors (AI) have been extensively studied in this setting. This section summarizes the key data regarding the use of AI in advanced breast cancer. In postmenopausal women, AI are the first line of treatment for untreated patients, or those who had prior AI treatment and progress after 12 months of adjuvant therapy. A longer disease-free interval and absence of visceral disease is associated with a better response. If tumors recur in less than 12 months, it is recommended that tamoxifen (TAM) or the estrogen-receptor antagonist fulvestrant (FUL) treatment be initiated. In the second-line setting, the best option after progression is the administration of either FUL or TAM. In the third-line setting, reintroduction of AI is considered an acceptable option. In premenopausal women who have not received prior treatment or who have progressed after 12 months following adjuvant treatment, it is recommended to initiate therapy with a combination of TAM and a luteinizing hormone-releasing hormone (LHRH) analog. If there is treatment failure with the use of this combination, megestrol acetate or an LHRH agonist plus an AI may be reasonable alternatives. Intensive research is ongoing to understand the mechanisms of resistance to hormone therapy. In human epidermal growth factor receptor 2 positive-patients, combinations with HER2 antagonists are associated with significant clinical activity.

Hormonal modulation in the treatment of breast cancer

This article explores the history of endocrine therapy for the treatment of breast cancer, the clinical evidence behind the current standards of care, and controversies that may change these standards in the future.

Assessment of quality of life in advanced breast cancer. An overview of randomized phase III trials

BACKGROUND

Health-related quality of life (HRQOL) parameters are often used as end points in phase III trials in advanced breast cancer. The frequency and correlates of significant gains in HRQOL have not been assessed.

METHODS

To evaluate the contemporary role for HRQOL assessment in advanced breast cancer, we searched PubMed for the main and companion papers reporting the results of phase III trials on systemic antineoplastic therapies published between 1/98 and 7/09 in 11 leading journals.

RESULTS

The search yielded 87 trials that enrolled a total of 33,669 patients. HRQOL was mentioned/reported in the main paper in 34 trials, reported in a companion paper in one (a total of 35/87=40%), and mentioned in the abstract of the main paper in 19/34 cases (56%). There was no temporal trend for reporting on HRQOL in the two 6-year periods. Although formal statistical comparisons were reported in 31/35 cases (89%), a significant difference was found in only 4/31 (13%) trials, always favoring the experimental arm. Given the small number of studies with a significant HRQOL finding, we could not assess correlates of gain in HRQOL.

CONCLUSIONS

HRQOL is one of the key indicators of treatment benefit in advanced breast cancer, but contemporary systemic therapies in this setting do not appear to affect HRQOL differentially.

Optimal management of bone metastases in breast cancer patients

Bone metastasis in breast cancer is a significant clinical problem. It not only indicates incurable disease with a guarded prognosis, but is also associated with skeletal-related morbidities including bone pain, pathological fractures, spinal cord compression, and hypercalcemia. In recent years, the mechanism of bone metastasis has been further elucidated. Bone metastasis involves a vicious cycle of close interaction between the tumor and the bone microenvironment. In patients with bone metastases, the goal of management is to prevent further skeletal-related events, manage complications, reduce bone pain, and improve quality of life. Bisphosphonates are a proven therapy for the above indications. Recently, a drug of a different class, the RANK ligand antibody, denosumab, has been shown to reduce skeletal-related events more than the bisphosphonate, zoledronic acid. Other strategies of clinical value may include surgery, radiotherapy, radiopharmaceuticals, and, of course, effective systemic therapy. In early breast cancer, bisphosphonates may have an antitumor effect and prevent both bone and non-bone metastases. Whilst two important Phase III trials with conflicting results have led to controversy in this topic, final results from these and other key Phase III trials must still be awaited before a firm conclusion can be drawn about the use of bisphosphonates in this setting. Advances in bone markers, predictive biomarkers, multi-imaging modalities, and the introduction of novel agents have ushered in a new era of proactive management for bone metastases in breast cancer.

Aromatase, aromatase inhibitors, and breast cancer

Estrogens are known to be important in the growth of breast cancers in both pre and postmenopausal women. As the number of breast cancer patients increases with age, the majority of breast cancer patients are postmenopausal women. Although estrogens are no longer made in the ovaries after menopause, peripheral tissues produce sufficient concentrations to stimulate tumor growth. As aromatase catalyzes the final and rate-limiting step in the biosynthesis of estrogen, inhibitors of this enzyme are effective targeted therapy for breast cancer. Three aromatase inhibitors (AIs) are now FDA approved and have been shown to be more effective than the antiestrogen tamoxifen and are well tolerated. AIs are now a standard treatment for postmenopausal patients. AIs are effective in adjuvant and first-line metastatic setting. This review describes the development of AIs and their current use in breast cancer. Recent research focuses on elucidating mechanisms of acquired resistance that may develop in some patients with long term AI treatment and also in innate resistance. Preclinical data in resistance models demonstrated that the crosstalk between ER and other signaling pathways particularly MAPK and PI3K/Akt is an important resistant mechanism. Blockade of these other signaling pathways is an attractive strategy to circumvent the resistance to AI therapy in breast cancer. Several clinical trials are ongoing to evaluate the role of these novel targeted therapies to reverse resistance to AIs. Article from the special issue on 'Targeted Inhibitors'.

Hormonal therapy plus bevacizumab in postmenopausal patients who have hormone receptor-positive metastatic breast cancer: a phase II Trial of the Sarah Cannon Oncology Research Consortium

PURPOSE

Preclinical models suggest that addition of anti-vascular endothelial growth factor therapy may improve the efficacy of anti-estrogens in hormone-sensitive breast cancer. This phase II trial evaluated the feasibility and efficacy of bevacizumab added to either anastrozole or fulvestrant in the first-line treatment of patients who have hormone receptor-positive metastatic breast cancer.

METHODS

Women who had newly diagnosed metastatic hormone receptor-positive breast cancer were eligible. Patients who had relapsed while receiving, or ≤ 12 months after receiving, adjuvant aromatase inhibitor therapy were treated with bevacizumab (10 mg/kg intravenously every 2 weeks) and fulvestrant (loading dose 500 mg intramuscularly [IM], then 250 mg IM 2 weeks later, then 250 mg IM every 4 weeks). All other patients received fulvestrant/bevacizumab or anastrozole (1 mg orally daily)/bevacizumab. Patients who were HER2-positive could also receive trastuzumab (8 mg/kg loading dose, then 6 mg/kg every 3 weeks). Patients were reevaluated after 8 weeks of therapy; responding or stable patients continued treatment until disease progression or unacceptable toxicity.

RESULTS

Seventy-nine patients were enrolled (38 were administered anastrozole 41 fulvestrant). Median treatment duration was 8 months in the anastrozole group and 5.5 months in the fulvestrant group. Both regimens were efficacious: overall response rate and median progression-free survival for the entire group were 28% and 13.5 months, respectively. Both regimens were well-tolerated; toxicity was consistent with the known toxicity profiles of each single agent.

CONCLUSION

Bevacizumab combined with either anastrozole or fulvestrant was feasible and active in the first-line treatment of patients who have hormone receptor-positive metastatic breast cancer. Phase III trials evaluating the efficacy of bevacizumab added to endocrine therapy are in progress.

Treatment of metastatic breast cancer: state-of-the-art, subtypes and perspectives

Current treatment of metastatic breast cancer (MBC) aims at achieving meaningful clinical responses, improved quality of life, long-term remissions, prolonged survival, and dares to hope for a cure in a small percentage of cases. This article will discuss both consensus and controversies in the management of MBC in the context of the new evolving breast cancer molecular classification. Hormonal therapy remains the mainstay of management of MBC Luminal A and B. Data is emerging on management of ErbB2-positive HR-positive MBC by combining hormonal manipulation and targeted anti-ErbB2 therapy and has recently received regulatory approval in Europe and USA. The optimal use and duration of single agent or combination chemotherapy is discussed. Data and controversies surrounding the use of newer agents such as nab-paclitaxel, ixabepilone, eribulin, and PARP inhibitors as well as trastuzumab is reviewed. Better understanding of pathophysiology has paved the way for the introduction of newer anti-ErbB2 agents such as lapatinib, pertuzumab, T-DM1 and neratinib. Controversies regarding bevacizumab and anti-angiogenesis are discussed. Bisphosphonates have significantly reduced skeletal related events and made significant improvements in the quality of life of patients with MBC. Newer anti-RANK Ligand antibodies show promising results. Significant advances in the understanding of molecular biology of breast cancer have been made and should lead to an improvement in the outcome of MBC. More possibilities of cure can become an attainable goal in the near future.

Endocrine therapy for male breast cancer: rates of toxicity and adherence

PURPOSE

Most male breast cancer tumours are hormone receptor-positive; the patients therefore receive endocrine therapy. There is, however, a paucity of published data on toxicities experienced by male breast cancer patients who are prescribed endocrine therapy. In the present study, we examined rates of adherence to and toxicity from endocrine treatments in male breast cancer patients treated at a single institution.

PATIENTS AND METHODS

We conducted a retrospective study of male patients diagnosed with breast cancer at The Ottawa Hospital Cancer Centre during 1981-2003. Data collected included patient age, hormone receptor status, therapy adherence, self-reported toxicities, and type and duration of endocrine therapies.

RESULTS

The review located 59 cases of early-stage and metastatic male breast cancer. Median patient age was 68.0 years. Tamoxifen was given to 38 patients (64.4%), anastrozole to 8 (13.6%), and letrozole to 5 (8.5%). Of patients who received endocrine therapy, 10 (25%) received adjuvant systemic chemotherapy. Toxicity was reported by 19 patients taking tamoxifen (50%), with hot flashes being the most common complaint (18.4%). Decreased libido, weight gain, and malaise were reported by 5 patients (13.2%). Rash and erectile dysfunction were reported by 3 patients (7.9%). Increased liver enzymes, pulmonary embolism, superficial thrombophlebitis, myalgia, depression, visual blurring, and loose stools were each reported in 1 patient (2.6%). Tamoxifen therapy was discontinued secondary to toxicity in 9 patients (23.7%). Of the patients treated with anastrozole, 3 (37.5%) reported toxicity, with 1 report each of decreased libido, leg swelling, and depression (12.5%). Toxicity was reported in 2 patients taking letrozole (40%), with both reporting peripheral edema, and 1 reporting hot flashes. No patient discontinued anastrozole or letrozole because of toxicity.

CONCLUSIONS

Few studies specifically report data on adherence to and toxicities from endocrine therapies in male breast cancer patients. The rate of discontinuation at our institution because of toxicity (23.7%) is similar to that reported in the female breast cancer population. Future prospective studies should explore strategies to improve adherence to endocrine therapy in this population.

Recurrent endometrial stromal sarcoma: treatment with a progestin and gonadotropin releasing hormone agonist

Endometrial stromal sarcoma (ESS) formerly classified as low-grade endometrial stromal sarcoma is a rare uterine malignancy with a good prognosis despite a tendency to recur. Primary surgical management for ESS includes total abdominal hysterectomy and bilateral salpingo-oophorectomy. Patients with ESS have long disease-free survival rates when treated with primary surgical therapy, but nearly fifty percent of these patients will recur. We present the case of a patient with recurrent ESS who had an excellent response to combined therapy with megestrol and leuprolide.

Letrozole

IMPORTANCE OF THE FIELD

Aromatase is an enzyme which converts adrenal androgens to estrogens in postmenopausal women. Given the importance of estrogens in breast cancer growth, aromatase inhibitors are used to treat breast cancer in different settings. This review focuses on letrozole, a third generation aromatase inhibitor, encompassing pharmacodynamic and pharmacokinetic aspects as well as its clinical efficacy and safety.

AREAS COVERED IN THIS REVIEW

A literature search and review of the studies published on letrozole were carried out using the MEDLINE database up to November 2009.

WHAT THE READER WILL GAIN

The paper provides the reader with information about pharmacodynamic and pharmacokinetic aspects of letrozole, its preclinical and clinical efficacy and its safety.

TAKE HOME MESSAGE

Letrozole is a well-tolerated and effective drug in metastatic breast cancer in postmenopausal women. Two clinical trials conducted in early breast cancer have confirmed its role in the adjuvant setting in postmenopausal women. More recently, data have confirmed its efficacy as neoadjuvant treatment in breast cancer. Future developments include the combination of letrozole with new biologic agents and tailoring of treatment with gene expression profiling studies.

The prognostic significance of single hormone receptor positive metastatic breast cancer: an analysis of three randomised phase III trials of aromatase inhibitors

We analysed the outcomes of women with metastatic breast cancer (MBC) from three randomised phase III trials of aromatase inhibitors according to oestrogen receptor (ER) and progesterone receptor (PgR) status. Both receptors were analysed in 1010 of the 1870 women (54%), including 31 that were ER-/PgR-, which were excluded. Of the remaining 979, 726 (74%) were ER+/PgR+ but 253 were single hormone receptor positive (213 ER+/PgR-, 40 ER-/PgR+). Although there were no differences in clinical benefit or time to progression, the median overall survival of women with ER+/PgR+ tumours was significantly longer than those with single HR positive tumours (800 versus 600 days, p=0.01). In women with ER+ tumours, the median overall survival of those with tumours that were also PgR+ was significantly longer than those that were PgR- (800 versus 625 days, p=0.02). The PgR status is an important prognostic factor for survival in MBC.

The National Cancer Institute of Canada Clinical Trials Group MAP.3 trial: an international breast cancer prevention trial

Several large phase iii trials have demonstrated that tamoxifen—and more recently, raloxifene—can effectively reduce the incidence of invasive breast cancer by 50%. However, these selective estrogen receptor modulators can also be associated with several rare, but serious, adverse events. Recently, the third-generation aromatase inhibitors (ais) have demonstrated excellent efficacy in adjuvant breast cancer trials, and they show particular promise in the breast cancer prevention setting. The National Cancer Institute of Canada Clinical Trials Group (ncic ctg) has developed a randomized phase iii study to determine the efficacy of an ai (exemestane) to reduce the incidence of invasive breast cancer in postmenopausal women at an increased risk for developing breast cancer. The ncic ctg map.3 (ExCel) trial is a double-blind placebo-controlled multicentre, multinational trial. Based on the known preclinical and clinical profile of the ais, a greater reduction in breast cancer incidence with fewer side effects is hypothesized with this class of agents than with tamoxifen or raloxifene.

Breast cancer: beyond the cutting edge

Remarkable progress has been made in the treatment of breast cancer over the past 100 years. The ability to probe at the genomic level increased our understanding of the disease but the improved survival outcomes can also be attributed to screening programs, which have altered the pattern of diagnosis and prognosis, and to a number of groundbreaking clinical trials. Indeed, the latter are largely responsible for the most startling paradigm reversals in oncology; namely, that optimal benefit can be achieved with minimal, rather than maximal, intervention. As such, surgical lumpectomy can replace the radical mastectomy, sentinel node biopsy may circumvent the need for complete (axillary) nodal dissection, hormonal therapy--depending on tumor sensitivity to endocrine manipulation--is likely to be beneficial without the addition of chemotherapy, and some targeted therapies can be used selectively in those most likely to benefit. However, despite the advances, controversies remain; patients die; and cure remains elusive.

Fulvestrant in advanced breast cancer following tamoxifen and aromatase inhibition: a single center experience

Fulvestrant is a pure estrogen receptor (ER) antagonist with no agonist effects. We describe the experience of a single center involving 45 postmenopausal women with advanced breast cancer where fulvestrant was utilized following progression on tamoxifen and a third generation aromatase inhibitor. Patients received fulvestrant as first line one (2%), second line 18 (40%), third line 13 (29%), fourth line 10 (22%), and fifth line three (7%) treatment. Median duration of treatment with Fulvestrant was 4 months (range 1-20 months). One patient had a partial response, 14 other (31%) experienced clinical benefit (CB) (defined as response or stable disease for at least 6 months). The median time to progression (TTP) from initiation of fulvestrant was 4 months (range 1-20 months) and the median survival was 10 months (range 1-55 months). In those patients who experienced CB the median TTP was 10 months (range 6-20) and median survival was 21 months (range 7-55). Fulvestrant was well tolerated; two patients experienced side effects severe enough to stop therapy. Despite the fact that fulvestrant was used in the majority of cases, later in the treatment sequence CB was seen in a number of patients. This data suggest fulvestrant is well tolerated and is a useful treatment option in patients with advanced breast cancer who progress on prior endocrine treatment.

Aromatase inhibitors for treatment of advanced breast cancer in postmenopausal women

BACKGROUND

Endocrine therapy removes the influence of oestrogen on breast cancer cells and so hormonal treatments such as tamoxifen, megestrol acetate and medroxyprogesterone acetate have been in use for many years for advanced breast cancer. Aromatase inhibitors (AIs) inhibit oestrogen synthesis in the peripheral tissues and have a similar tumour-regressing effect to other endocrine treatments. Aminoglutethimide was the first AI in clinical use and now the third generation AIs, anastrozole, exemestane and letrozole, are in current use. Randomised trial evidence on response rates and side effects of these drugs is still limited.

OBJECTIVES

To compare AIs to other endocrine therapy in the treatment of advanced breast cancer in postmenopausal women.

SEARCH STRATEGY

For this update, the Cochrane Breast Cancer Group Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL) and relevant conference proceedings were searched (to 30 June 2008).

SELECTION CRITERIA

Randomised controlled trials in postmenopausal women comparing the effects of any AI versus other endocrine therapy, no endocrine therapy, or a different AI in the treatment of advanced (metastatic) breast cancer. Non-English language publications, comparisons of the same AI at different doses, AIs used as neoadjuvant treatment, or outcomes not related to tumour response were excluded.

DATA COLLECTION AND ANALYSIS

Data from published trials were extracted independently by two review authors and cross-checked by a third. Hazard ratios (HR) were derived for analysis of time-to-event outcomes (overall and progression-free survival). Odds ratios (OR) were derived for objective response, clinical benefit, and toxicity.

MAIN RESULTS

Thirty-seven trials were identified, 31 of which were included in the main analysis of any AI versus any other treatment (11,403 women). No trials were excluded due to inadequate allocation concealment. The pooled estimate showed a significant survival benefit for treatment with an AI over other endocrine therapies (HR 0.90, 95% CI 0.84 to 0.97). A subgroup analysis of the three commonly prescribed AIs (anastrozole, exemestane, letrozole) also showed a similar survival benefit (HR 0.88, 95% CI 0.80 to 0.96). There were very limited data to compare one AI with a different AI, but these suggested an advantage for letrozole over anastrozole.AIs have a different toxicity profile to other endocrine therapies. For those currently prescribed, and for all AIs combined, they had similar levels of hot flushes and arthralgia; increased risks of rash, nausea, diarrhoea and vomiting; but a 71% decreased risk of vaginal bleeding and 47% decrease in thromboembolic events compared with other endocrine therapies.

AUTHORS' CONCLUSIONS

In women with advanced (metastatic) breast cancer, aromatase inhibitors including those in current clinical use show a survival benefit when compared to other endocrine therapy.

Data from the Arimidex, Tamoxifen, Alone or in Combination (ATAC) Trial

The third-generation aromatase inhibitors (AIs) have improved efficacy and safety versus tamoxifen for treatment of advanced breast cancer. Currently, anastrozole is the only third-generation AI with adjuvant therapy data in postmenopausal women. Initial and updated results from the Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial (median follow-up, 47 months) confirm it to be more effective than tamoxifen for disease-free survival with several important tolerability benefits. As a result, there has been much debate about whether or not anastrozole should be used routinely to treat postmenopausal women with early breast cancer. In its review, the American Society of Clinical Oncology Health Services Research Committee agreed that the updated ATAC analyses provided a greater level of assurance, in terms of both toxicity and efficacy, for use of anastrozole in the adjuvant setting. However, pending 5-year data from ATAC and other trials of adjuvant AI use, adjuvant anastrozole was recommended by American Society of Clinical Oncology Health Research Committee for use only under certain circumstances, with 5 years of tamoxifen remaining the standard. Anastrozole should be the preferred AI in this setting; data from the ATAC trial should not be extrapolated to other members of the class. Despite this conservative recommendation, the overall risk:benefit profile from the ATAC trial favors anastrozole, and it is expected that a more favorable efficacy and adverse effect profile will be maintained. Anastrozole should, therefore, now be considered a valid alternative option to tamoxifen for adjuvant hormonal treatment in all postmenopausal women with hormone receptor-positive early breast cancer.

Sequencing of Endocrine Therapy in Postmenopausal Women with Advanced Breast Cancer

The introduction of the nonsteroidal aromatase inhibitor (NS-AI) anastrozole as an alternative to tamoxifen for adjuvant therapy of women with resected hormone receptor-positive breast cancer has added a management category into which patients presenting with metastatic disease can be placed. There are now essentially three such categories: (a) tamoxifen sensitive (no prior AI); (b) tamoxifen resistant (no prior AI); and (c) NS-AI resistant (no prior tamoxifen). Well-conducted Phase III trials provide evidence for choosing first-line therapy for advanced disease in categories a and b. In tamoxifen-sensitive patients, one can choose either NS-AI, anastrozole, or letrozole. In tamoxifen-resistant patients, one can choose either of the NS-AIs, the steroidal AI exemestane, or the estrogen receptor down-regulator fulvestrant. The situation is quite different for patients in category c. There are no Phase III trials of agents in patients who have experienced disease progression on a NS-AI. Phase II data are available for exemestane and high-dose estrogens, and retrospective data are available for tamoxifen and fulvestrant. Additional clinical trials are needed to determine an optimal sequencing strategy.

Metastatic breast cancer: therapeutic options according to molecular subtypes and prior adjuvant therapy

In spite of advances in treatment strategies, about 25%-40% of patients with breast cancer still eventually develop metastatic disease that is largely incurable. Treatment goals vary from symptom control to lengthening survival, mainly on the basis of patient age and performance status, tumor biology, site and extent of disease, and prior therapies. In particular, breast cancer molecular characterization allows for the identification of breast cancer subtypes with distinct biological features, a distinct clinical course, and distinct treatment sensitivity. Endocrine manipulation is the cornerstone of therapy in hormone receptor-positive tumors; anti-human epidermal growth factor receptor (HER)-2 agents are essential in the management of HER-2(+) tumors; and chemotherapy is the only available option so far for the triple-negative subtype. In each of these subtypes, the more efficacious agents have been progressively incorporated into adjuvant treatment. As a consequence, the choice of the optimal therapeutic strategy for patients with metastatic disease is largely influenced by prior exposure to adjuvant therapies. This review contextualizes the data from clinical trials into different clinical scenarios of metastatic disease, taking into account the molecular subtype and prior adjuvant treatments.

Preclinical and Clinical Experience with Fulvestrant (Faslodex) in Postmenopausal Women with Hormone Receptor-Positive Advanced Breast Cancer

Fulvestrant (Faslodex) is a new type of estrogen receptor (ER) antagonist that binds, blocks, and degrades the ER, leading to reduced expression of the progesterone receptor (PgR). Unlike the selective ER modulator tamoxifen, fulvestrant is devoid of any known agonist activity. Fulvestrant has a steroidal structure that competitively binds to the ER with an affinity much greater than that of tamoxifen. After binding to fulvestrant, degradation of the ER is accelerated, ultimately resulting in a reduction in cellular ER. Immunohistochemical studies have demonstrated that a single intramuscular injection of fulvestrant results in a dose-dependent decrease in ER and PgR indices and in Ki-67 expression. At the approved 250 mg dose, the decrease in receptor positivity with fulvestrant treatment was greater than that with tamoxifen. Phase III clinical trials have demonstrated the clinical benefit of fulvestrant in the endocrine treatment of breast cancer. Among patients who progressed during adjuvant or first-line endocrine therapy, fulvestrant was at least as effective as anastrozole as second-line treatment for the primary endpoints of objective response and time to progression, and was well tolerated. After a median follow-up of 24.5 months, a combined survival analysis from two Phase III studies has shown that fulvestrant may be considered similar to anastrozole for time to death (27.4 months versus 27.7 months, respectively). For the first-line therapy of advanced breast cancer in postmenopausal women, fulvestrant was shown to be active and well tolerated in a trial that compared fulvestrant 250 mg once monthly and tamoxifen 20 mg once daily. Treatment with fulvestrant has also demonstrated clinical efficacy among patients who progressed following treatment with tamoxifen followed by nonsteroidal aromatase inhibitors. The efficacy of fulvestrant in sequential endocrine therapy and in combination with other agents appears promising and active investigations are ongoing to explore the clinical potential of this novel antiestrogen.

Clinical Evaluation of the Use of Exemestane as Further Hormonal Therapy after Nonsteroidal Aromatase Inhibitors in Postmenopausal Metastatic Breast Cancer Patients

OBJECTIVES

The aromatase inhibitors Anastrozole, Letrozole (type 2 nonsteroidal aromatase inhibitors: n-SAI) and Exemestane (type 1 steroidal aromatase inactivator) are used respectively as first- and second-line hormonal therapy in postmenopausal metastatic breast cancer women. Few clinical data are published on the sequential use of different classes of aromatase inhibitors.

METHODS

We report an analysis on 30 postmenopausal metastatic breast cancer women treated between January 2000 and May 2002 in 2 Italian Oncology Institutions with the hormonal sequence n-SAI (Anastrozole, Letrozole) --> Exemestane.

RESULTS

When receiving n-SAI (Anastrozole 8 patients and Letrozole 22 patients), 1 out of 30 women achieved a partial response, 20 of 30 patients no change (NC) > or =6 months. The analysis of the entire population treated with Exemestane showed an overall clinical benefit (CB) of 46.6 percent (14/30) with a median duration of 12 months (95%CI 6-25) and a median time to progression (TTP) of 4 months (95%CI 1-25).

CONCLUSIONS

These data confirm a partial lack of cross-resistance between n-SAI --> Exemestane given in sequence.

Treatment of established breast cancer in post-menopausal women: role of aromatase inhibitors

Endocrine therapy plays a crucial and historically important role in the treatment ofwomen with hormone-responsive breast cancer. Tamoxifen has been the standard endocrine treatment for advanced and early-stage breast cancer for almost three decades. However, patients receiving tamoxifen may either fail to respond or develop disease recurrence following completion of therapy. The aromatase inhibitors (Als) have become the new and alternative modalities of endocrine treatment for post-menopausal women with oestrogen receptor-positive breast cancer, as a result of promising data from randomised trials in metastatic and locally advanced breast cancers. Recently, the results from several large, randomised, controlled adjuvant trials have provided further evidence that the use of Als, either as initial treatment or sequentially after tamoxifen, improves disease-free survival and, in certain patients, overall survival. With relatively short-term follow-up, the use of Als has been shown to be safe and welltolerated. Nevertheless, some detrimental adverse effects, particularly skeletal-related events or cardiovascular disease, remain important issues of concern and warrant continued monitoring and follow-up. The optimal use of Als, the appropriate timing of treatment, and the superiority of individual agents are under investigation. Use of Als in women with chemotherapy-induced amenorrhoea should be cautious due to the possibility of return of ovarian function. Cost-effectiveness and quality of life remain issues of interest since the high and ever increasing incidence of breast cancer has contributed to significant healthcare costs and patients with breast cancer following appropriate treatment are living longer but not necessarily being cured of their diseases.

Optimal treatment strategies in postmenopausal women with hormone-receptor-positive and HER2-negative metastatic breast cancer

Metastatic breast cancer (MBC) is unfortunately still considered incurable; treatment aims to prolong progression-free and overall survival, relieve disease symptoms, and maintain quality of life. Treatment can include endocrine therapy, radiotherapy, chemotherapy, bisphosphonates, and/or targeted therapy; which is used depends on the characteristics of the disease [e.g., hormone receptor status, disease site(s), and response to previous treatment] and the patient (age, comorbidity, and personal preferences). For most patients with hormone-receptor-positive tumors, the first choice of treatment is further endocrine therapy, but endocrine resistance is a common problem in advanced disease. Several novel anticancer agents have been developed with the aim of overcoming endocrine resistance, many of which target intracellular signaling pathways implicated in disease progression or resistance. Among these, inhibitors of growth factor receptor tyrosine kinases and of mammalian target of rapamycin have shown the most promise in clinical trials. Chemotherapy is the cornerstone of MBC treatment in most women. Important considerations when choosing chemotherapy include the choice of agents, and whether to use single-agent or combination therapy. Anthracyclines are one of the most active cytotoxic agents currently used for the treatment of breast cancer, and for many women, further anthracycline therapy at progression or relapse would be the preferred option. However, lifetime exposure to anthracyclines is limited by cumulative cardiotoxicity, which often prevents rechallenge in later lines of therapy. Newer anthracycline formulations have been developed with lower cardiotoxicity than the conventional anthracycline doxorubicin, but these agents still impair cardiac function, and have maximum recommended lifetime doses. Recently, the concomitant use of cardioprotective agents, such as dexrazoxane, has emerged as an effective approach to reducing the cardiotoxic effects of anthracyclines, thus permitting retreatment. Bisphosphonates, which are not associated with the acute toxicities of cytotoxic chemotherapy drugs, are the established standard of care for patients with metastatic bone disease, and have greatly improved outcomes over the last decade. The search is ongoing for novel agents that will, hopefully, bring a cure closer to reality.

Biologic therapy of breast cancer: focus on co-inhibition of endocrine and angiogenesis pathways

There remains a high unmet need for effective treatments for metastatic breast cancer. In recent years there have been many advances in the understanding of biological basis of cancer. Several cellular pathways have been identified that play crucial roles in causing or maintaining the cancer phenotype. Many new agents that target these pathways have entered the clinic or are being investigated. In order to improve the therapeutic efficacy seen with single-agent regimens, rational combinations of targeted agents are being evaluated in ongoing trials. The optimal sequencing and combination of agents has yet to be established. Endocrine and vascular endothelial growth factor pathways are the two most prominent pathways active in breast cancer cells and inhibition of either of these is associated with clinical benefit. Here we discuss the rationale for simultaneously targeting these pathways and highlight ongoing clinical trials.

Lack of complete cross-resistance between different aromatase inhibitors; a real finding in search for an explanation?

While third-generation aromatase inhibitors (anastrozole, letrozole and exemestane) are successfully implemented as adjuvant and first-line therapy for hormone-sensitive breast cancer in postmenopausal women, important questions remain to be addressed. An issue of particular interest is the question about lack of complete cross-resistance between steroidal and non-steroidal compounds. Although the studies reporting this phenomenon in general contain a small number of patients, the findings across the different reports seem consistent. While several potential mechanisms have been suggested, so far we lack scientific proof what mechanisms may be responsible for this finding. Finally, we do not know whether lack of cross-resistance actually signals an improved efficacy for certain compounds or may be due to alternative mechanisms of action. Neither do we know whether some tumours are more sensitive to particular drugs. This paper summarizes clinical findings up to now with respect to lack of cross-resistance and discuss potential mechanisms involved.

Molecular mechanisms of endocrine resistance and their implication in the therapy of breast cancer

The use of endocrine agents is a safe and effective treatment in the management of hormone-sensitive breast cancer. Unfortunately, sooner or later, tumor cells develop resistance to endocrine manipulation making useless this approach. During the last decade, new molecules and intracellular signaling pathways involved in endocrine resistance have been identified. Several studies have documented that estrogen receptor signaling may maintain a pivotal role in the tumor growth despite the failure of a previous hormonal treatment. In this review we will discuss the general principles for optimizing the choice of endocrine therapy based on an understanding of the molecular mechanisms responsible for resistance to the different anti-hormonal agents.

Randomized trial of denosumab in patients receiving adjuvant aromatase inhibitors for nonmetastatic breast cancer

PURPOSE

Adjuvant aromatase inhibitor therapy is well established in postmenopausal women with hormone receptor-positive breast cancer, but such therapy is complicated by accelerated bone loss and increased fracture risk. We investigated the ability of denosumab, a fully human monoclonal antibody against receptor activator of nuclear factor-kappaB ligand, to protect against aromatase inhibitor-induced bone loss.

PATIENTS AND METHODS

Eligible women with hormone receptor-positive nonmetastatic breast cancer treated with adjuvant aromatase inhibitor therapy were stratified by duration of aromatase inhibitor therapy (< or = 6 v > 6 months), received supplemental calcium and vitamin D, and were randomly assigned to receive placebo (n = 125) or subcutaneous denosumab 60 mg (n = 127) every 6 months. At enrollment, all patients were required to have evidence of low bone mass, excluding osteoporosis. The primary end point was percentage change from baseline at month 12 in lumbar spine bone mineral density (BMD).

RESULTS

At 12 and 24 months, lumbar spine BMD increased by 5.5% and 7.6%, respectively, in the denosumab group versus placebo (P < .0001 at both time points). Increases were observed as early as 1 month and were not influenced by duration of aromatase inhibitor therapy. Increases in BMD were also observed at the total hip, total body, femoral neck, and the predominantly cortical one-third radius. Bone turnover markers decreased with denosumab treatment. Overall incidence of treatment-emergent adverse events (AEs) was similar between treatment groups.

CONCLUSION

In women with nonmetastatic breast cancer and low bone mass who were receiving adjuvant aromatase inhibitor therapy, twice-yearly administration of denosumab led to significant increases in BMD over 24 months at trabecular and cortical bone, with overall AE rates similar to those of placebo.

Fulvestrant for systemic therapy of locally advanced or metastatic breast cancer in postmenopausal women: a systematic review

A systematic review was undertaken to examine all available evidence to develop and support clinical recommendations regarding the use of fulvestrant (Faslodex((R))) as systemic therapy of locally advanced or metastatic breast cancer in postmenopausal women. MEDLINE, EMBASE, American Society of Clinical Oncology Annual Meeting proceedings, San Antonio Breast Cancer Symposia proceedings, and the Cochrane Library were searched through to April of 2008 for reports of randomized controlled trials that met established inclusion criteria. Four relevant Phase III trials were available for inclusion based on established criteria. Three of four Phase III superiority trials found no significant difference between fulvestrant and control, either anastrozole or exemestane, across efficacy and safety endpoints following prior endocrine therapy failure, with two trials further confirming non-inferiority of fulvestrant to anastrozole retrospectively. Fulvestrant can therefore be considered as alternative therapy to anastrozole or exemestane in postmenopausal women with locally advanced or metastatic breast cancer that has recurred on prior adjuvant endocrine therapy or progressed on prior endocrine therapy for advanced disease. There are, however, important methodological concerns across reviewed trials that should be taken under consideration as they may limit the strength of such a conclusion.

[Adjuvant endocrine therapy in postmenopausal hormone-sensitive breast cancer: to start, to switch or to extend?]

From the big randomized clinical trials there are evidences that adjuvant endocrine therapy for hormone-sensitive early breast cancer in postmenopausal women should include an aromatase inhibitor (AI). Anastrozole or letrozole should be used upfront for 5 years (ATAC and BIG 1-98), the sequential approach of tamoxifen for 2-3 years, followed by anastrozole or exemestane for 2-3 years is a reasonable alternative (ABCSG8, ARNO 95, IES, ITA), and mostly in patients with node-positive disease completing 5 years of tamoxifen should be offered letrozole up to 4-5 years (MA-17). In each of these trials incorporation of an AI resulted in significant improvement in study endpoints. Further results will be needed to establish the optimal beneficial effect, use, duration and safety of adjuvant AI therapies.

Update on aromatase inhibitors in breast cancer

PURPOSE OF REVIEW

Hormonal treatment is one of the cornerstones of management for breast cancer. For many years, tamoxifen represented the gold standard. The development of aromatase inhibitors has, however, challenged the primary role of tamoxifen. Randomized studies evaluating the role of aromatase inhibitors in both the metastatic and adjuvant settings, in postmenopausal women, have been conducted. This article describes the most recent available data for these trials.

RECENT FINDINGS

The efficacy of aromatase inhibitors for metastatic disease is well established and has not changed recently. Multiple adjuvant aromatase inhibitor trials have been completed and published or presented. These trials vary in the timing of aromatase inhibitor administration, but all show statistically significant reductions in breast-cancer recurrence. An improvement in overall survival has not been observed to date. Tolerability is improved with aromatase inhibitors, the major concern with the use of aromatase inhibitors being the development of osteoporosis and bone fractures.

SUMMARY

Aromatase inhibitors are consistently showing improved efficacy and tolerability to tamoxifen for both early and advanced breast cancer. Optimal therapy for postmenopausal women should include an aromatase inhibitor. The optimal sequence of aromatase inhibitors and tamoxifen for adjuvant therapy is still, however, under investigation.

Aromatase inhibitors for breast cancer: proven efficacy across the spectrum of disease

For more than 100 years, hormonal therapy has been known to be effective in the treatment of breast cancer. Initially, this therapy was dominated by the selective estrogen receptor antagonists such as tamoxifen. Aromatase inhibitors (AIs) are a distinct drug class with demonstrated activity in the treatment of hormone-sensitive breast cancer. All 3 third-generation AIs, exemestane, anastrozole, and letrozole, have been studied in multiple lines of therapy in advanced breast cancer and have demonstrated equivalence or superiority compared with tamoxifen. While initially developed as a treatment option for advanced disease, the AIs have also shown efficacy in the treatment of curable disease, including the neoadjuvant and adjuvant settings. In addition, the AIs demonstrate a tolerable side effect profile in comparison with tamoxifen, and this has led to their early incorporation as standard of care therapy. Given the proven efficacy of AIs across the spectrum of breast cancer, the remaining questions include definitive sequencing strategy, timing, and duration of use. Ongoing trials include head-to-head comparisons between the AIs in early-stage breast cancer; the results of these trials are eagerly anticipated and should further optimize the use of AIs.