Anastrozole as an adjuvant endocrine treatment for postmenopausal patients with breast cancer: emerging data

Design, structure-activity relationships, and enzyme kinetic studies of tricyclic and tetracyclic coumarin-based sulfamates as steroid sulfatase inhibitors

Inhibition of steroid sulfatase (STS) decreases estrogen production and thus, suppresses tumor proliferation. Inspired by irosustat, the first STS inhibitor in clinical trials, we explored twenty-one tricyclic and tetra-heterocyclic coumarin-based derivatives. Their STS enzyme kinetic parameters, docking models, and cytotoxicity toward breast cancer and normal cells were evaluated. Tricyclic derivative 9e and tetracyclic derivative 10c were the most promising irreversible inhibitors developed in this study, with KI of 0.05 and 0.4 nM, and kinact/KI ratios of 28.6 and 19.1 nM-1min-1 on human placenta STS, respectively.

Aromatase inhibition increases blood pressure and markers of renal injury in female rats

Aromatase is a monooxygenase that catalyzes the rate-limiting step of estrogen biosynthesis from androgens. Aromatase inhibitors are widely used for the treatment of patients with hormone receptor-positive breast cancer. However, the effects of aromatase inhibitors on cardiovascular and renal health in females are understudied. Given that estrogen is protective against cardiovascular and kidney diseases, we hypothesized that aromatase inhibition elevates blood pressure and induces kidney injury in female Sprague-Dawley rats. Twelve-week-old female rats were implanted with radiotelemetry transmitters to continuously monitor blood pressure. After baseline blood pressure recording, rats were randomly assigned to treatment with the aromatase inhibitor anastrozole (ASZ) or vehicle (Veh) in drinking water. Twenty days after treatment initiation, rats were shifted from a normal-salt (NS) diet to a high-salt (HS) diet for an additional 40 days. Rats were euthanized 60 days after treatment initiation. Body weight increased in both groups over the study period, but the increase was greater in the ASZ-treated group than in the Veh-treated group. Mean arterial pressure increased in ASZ-treated rats during the NS and HS diet phases but remained unchanged in Veh-treated rats. In addition, urinary excretion of albumin and kidney injury marker-1 and plasma urea were increased in response to aromatase inhibition. Furthermore, histological assessment revealed that ASZ treatment increased morphological evidence of renal tubular injury and proximal tubular brush border loss. In conclusion, chronic aromatase inhibition in vivo with ASZ increases blood pressure and markers of renal proximal tubular injury in female Sprague-Dawley rats, suggesting an important role for aromatization in the maintenance cardiovascular and renal health in females.NEW & NOTEWORTHY Aromatase enzyme catalyzes the rate-limiting step in estrogen biosynthesis. Aromatase inhibitors are clinically used for the treatment of patients with breast cancer; however, the impact of inhibiting aromatization on blood pressure and renal function is incompletely understood. The present findings demonstrate that systemic anastrozole treatment increases blood pressure and renal tubular injury markers in female rats fed a high-salt diet, suggesting an important role for aromatization in preserving cardiovascular and renal health in females.

ER-α36: a novel biomarker and potential therapeutic target in breast cancer

Estrogen receptor-alpha36 (ER-α36) is a 36-kDa variant of estrogen receptor-alpha (ER-α) firstly identified and cloned by Wang et al in 2005. It lacks both transactivation domains (activation function 1 and activation function 2) and has different biological characteristics compared to traditional ER-α (ER-α66). ER-α36 primarily locates on plasma membrane and cytoplasm and functions as a mediator in the rapid membrane-initiated non-genomic signaling pathway. Additionally, it inhibits the traditional genomic signaling pathway mediated by ER-α66 in a dominant-negative pattern. Accumulating evidence has demonstrated that ER-α36 regulates the physiological function of various tissues. Thus, dysregulation of ER-α36 is closely associated with plenty of diseases including cancers. ER-α36 is recognized as a molecular abnormality which solidly correlates to carcinogenesis, aggressiveness, and therapeutic response of breast cancer. Additionally, special attention has been paid to the role of ER-α36 in endocrine therapy resistance. Therefore, ER-α36 provides a novel biomarker of great value for diagnosis, prognosis, and treatment of breast cancer. It may also be a potential therapeutic target for breast cancer patients, especially for those who are resistant to endocrine therapy. In this review, we will overview and update the biological characteristics, underlying mechanism, and function of ER-α36, focusing on its biological function in breast cancer and endocrine therapy resistance. We will evaluate its application value in clinical practice.

Management of bone disease in patients undergoing hormonal therapy for breast cancer

Estrogen deficiency at menopause is associated with increased risk of bone loss and osteoporosis. Aromatase inhibitors (AIs) are increasingly being used for the treatment of postmenopausal hormone-sensitive breast cancer because of better disease-free survival compared with tamoxifen seen in clinical trials with AIs. This article reviews the effect of endocrine therapies of breast cancer on bone and the management of bone disease with these endocrine therapies. The effect of these therapies on bone mineral density and bone turnover along with possible interventions is discussed. AIs are also associated with skeletal-related events, which are not discussed.

Correlation between docetaxel-induced skin toxicity and the use of steroids and H₂ blockers: a multi-institution survey

Steroids and H(2) blockers are commonly used as supportive care for taxane-containing chemotherapy, but they also affect docetaxel's primary metabolizer, cytochrome P(450) 3A4. This retrospective observational study was performed to better understand the effects of these compounds on docetaxel-induced skin toxicities, specifically hand-foot syndrome (HFS) and facial erythema (FE), a relationship that is currently poorly understood. Member institutions of the Japan Breast Cancer Research Group were invited to complete a questionnaire on the occurrence of grade 2 or higher HFS and FE among patients treated between April 2007 and March 2008 with docetaxel as an adjuvant or neoadjuvant chemotherapeutic treatment for breast cancer. We obtained data for 993 patients from 20 institutions. Twenty percent received H(2) blockers, and all patients received dexamethasone. Univariate and multivariate analyses revealed that H(2) blockers are associated with a significantly higher incidence of both HFS and FE. The incidence of FE was significantly higher for the docetaxel + cyclophosphamide (TC) regimen than for non-TC regimens combined. Dexamethasone usage did not affect the incidence of either HFS or FE. In conclusion, use of H(2) blockers as premedication in breast cancer patients receiving docetaxel significantly increases the risk of both HFS and FE.

Expression of ER-{alpha}36, a novel variant of estrogen receptor {alpha}, and resistance to tamoxifen treatment in breast cancer

PURPOSE Recently, a 36-kDa variant of estrogen receptor alpha (ER-alpha66), ER-alpha36, has been identified and cloned. ER-alpha36 predominantly localizes on the plasma membrane and in the cytoplasm and mediates a membrane-initiated "nongenomic" signaling pathway. Here, we investigate the association between ER-alpha36 expression and tamoxifen resistance in patients with breast cancer. PATIENTS AND METHODS ER-alpha36 protein expression in tumors from 896 women (two independent cohorts, 1 and 2) with operable primary breast cancer was assessed using an immunohistochemistry assay. Results In the first cohort of 710 consecutive patients, overexpression of ER-alpha36 was associated with poorer disease-free survival (DFS) and disease-specific survival (DSS) in patients with ER-alpha66-positive tumors who received tamoxifen treatment (chemotherapy plus tamoxifen or tamoxifen alone, n = 307). In contrast, ER-alpha36 was not associated with survival in patients with ER-alpha66-positive tumors who did not receive tamoxifen (chemotherapy alone, n = 129) and in patients with ER-alpha66-negative tumors whether they received tamoxifen (n = 73) or not (n = 149). In the second cohort of 186 patients who only received tamoxifen as adjuvant therapy, overexpression of ER-alpha36 was significantly associated with poorer DFS and DSS in 156 ER-alpha66-positive patients from this cohort, and ER-alpha36 remained an independent unfavorable factor for both DFS and DSS in these 156 patients by a multivariate analysis (DFS: hazard ratio [HR] = 5.47; 95% CI, 1.81 to 16.51; P =. 003; DSS: HR = 13.97; 95% CI, 1.58 to 123.53; P = .018). CONCLUSION Women with ER-alpha66-positive tumors that also express high levels of ER-alpha36 are less likely to benefit from tamoxifen treatment.

Meta-analysis of trials comparing anastrozole and tamoxifen for adjuvant treatment of postmenopausal women with early breast cancer

OBJECTIVE

It was aimed to review the literature and make a meta-analysis of the trials on both upfront, switching, and sequencing anastrozole in the adjuvant treatment of early breast cancer.

METHODS

The PubMed, ClinicalTrials.gov and Cochrane databases were systematically reviewed for randomized-controlled trials comparing anastrozole with tamoxifen in the adjuvant treatment of early breast cancer.

RESULTS

The combined hazard rate of 4 trials for event-free survival (EFS) was 0.77 (95%CI: 0.70-0.85) (P < 0.0001) for patients treated with anastrozole compared with tamoxifen. In the second analysis in which only ITA, ABCSG 8, and ARNO 95 trials were included and ATAC (upfront trial) was excluded, combined hazard rate for EFS was 0.64 (95%CI: 0.52-0.79) (P < 0.0001). In the third analysis including hazard rate for recurrence-free survival (excluding non-disease related deaths) of estrogen receptor-positive patients for ATAC trial and hazard rate for EFS of all patients for the rest of the trials, combined hazard rate was 0.73 (95%CI: 0.65-0.81) (P < 0.0001).

CONCLUSION

Anastrozole appears to have superior efficacy than tamoxifen in the adjuvant hormonal treatment of early breast cancer. Until further clinical evidence comes up, aromatase inhibitors should be the initial hormonal therapy in postmenopausal early breast cancer patients and switching should only be considered for patients who are currently receiving tamoxifen.

Association between CYP2D6 *10 genotype and survival of breast cancer patients receiving tamoxifen treatment

BACKGROUND

Human cytochrome P450 2D6 (CYP2D6) genotype may affect the efficacy of tamoxifen treatment in Caucasian women with breast cancer. The most common polymorphism of CYP2D6 in Chinese women is variant 10 (188 C to T).

PATIENTS AND METHODS

Tamoxifen and 4-hydroxytamoxifen (4OHtam) were measured in the serum of 37 women with breast cancer who were receiving tamoxifen treatment. The association between CYP2D6 *10 genotype and survival was determined in a cohort of 293 women with breast cancer who received tamoxifen (n = 152) or who did not (n = 141).

RESULTS

The serum 4OHtam concentrations were significantly lower in women with the CYP2D6 *10 homozygous variant T/T genotype than in those with the homozygous wild-type C/C genotype (P = 0.04). Among tamoxifen-treated women, women with the T/T genotype had a significantly worse disease-free survival (DFS) than those with the C/C or C/T genotype, and the T/T genotype remained an independent prognostic factor of DFS in multivariate analysis (hazard ratio = 4.7; 95% confidence interval = 1.1-20.0; P = 0.04). Among women who did not receive tamoxifen, there was no significant association between CYP2D6 *10 genotype and survival.

CONCLUSION

In tamoxifen-treated patients, women with the CYP2D6 *10 T/T genotype have a lower 4OHtam level in the serum and a worse clinical outcome.

A multidisciplinary approach to the management of breast cancer, part 2: therapeutic considerations

New approaches to breast cancer treatment have enhanced clinical outcomes and patient care. These approaches include advances in breast irradiation and hormonal and systemic adjuvant therapies. In addition to the identification of new drug targets and targeted therapeutics (eg, trastuzumab), there is renewed re-emphasis in the development of biomarkers for the prediction of response to therapy. One example is the pharmacogenetics of tamoxifen metabolism and the individualization of hormonal therapy. The current treatment of breast cancer continues to evolve rapidly, with new scientific and clinical achievements constantly changing the standard of care and leading to substantial reductions in breast cancer mortality. The goal of this article is to provide clinicians who care for women with breast cancer a multidisciplinary, state-of-the art approach to the treatment of these patients.

Adjuvant endocrine therapy for early breast cancer

Breast cancer is the most common cancer among women and about 80% of breast cancers express hormone receptors. Tamoxifen has been the most important form of adjuvant endocrine therapy over the last 25 years. The third generation aromatase inhibitors (AIs) are a new class of drugs challenging the central role of tamoxifen as adjuvant endocrine treatment in postmenopausal women with hormone receptor-positive breast cancer. Their effectiveness has been demonstrated in first line therapy as well in neoadjuvant setting with a statistically significant superiority over tamoxifen. Here we considered the role of adjuvant AIs in early stage breast cancer with an analysis reviewing the main adjuvant trials. We considered efficacy, side effects, optimal timing, duration of the therapy and whether specific subgroups may achieve particular benefit. In conclusion the upfront use of adjuvant anastrozole or letrozole is superior to tamoxifen with a good relative toxicity profile. Tamoxifen will continue to have a role where recurrence risk is low or if AI is poorly tolerated. Issues including the timing of administration (up-front or sequential), the duration of the therapy and the role of biomarkers such as PgR and HER2 in optimal selection remain unresolved.

Advances in hormonal therapy for breast cancer

OBJECTIVES

To describe recent developments in hormonal therapy for breast cancer, focusing on SERMs and AIs.

DATA SOURCES

Published journal articles and texts, research reports and monographs, government publications, and professional organization guidelines.

CONCLUSION

Research continues to identify the effectiveness of hormonal therapy in breast cancer, including adjuvant treatment in early and advanced stages as well as a chemopreventive measure. The individual drug profile must be evaluated for safety and efficacy, and the impact on QOL must be considered.

IMPLICATIONS FOR NURSING PRACTICE

It is imperative that oncology nurses understand the physiology, application, risks, and benefits of hormonal therapies.

Prevention of breast cancer: current state of the science and future opportunities

Despite significant progress in breast cancer treatment, mammary tumours still represent the second most frequent cause of cancer-related death in women in the US, with > 211,000 new cases in 2005; however, an expanding range of options for early diagnosis and more reliable risk assessment offers new alternatives for disease control by cancer prevention. Completed large studies with the classical selective estrogen receptor modulator (SERM) tamoxifen have demonstrated that preventing breast cancer pharmacologically is now possible. Novel SERMs, aromatase inhibitors and gonadotropin-releasing hormone agonists targeting hormonal pathways are being tested in clinical trials, revealing the potential for dramatic reductions in tumour incidence with minimal side effects; however, SERMs and aromatase inhibitors are effective only against estrogen receptor-positive tumours, thus chemopreventive drugs targeting other critical signalling pathways (such as retinoids, selective COX inhibitors and tyrosine kinase inhibitors) may provide a means to prevent estrogen receptor-negative breast cancer. In the future, hormonal and estrogen receptor-independent agents may be combined to prevent the development of all mammary tumours. This article reviews the current and novel strategies for breast cancer prevention.

Cost-utility of adjuvant hormone therapies with aromatase inhibitors in post-menopausal women with breast cancer: upfront anastrozole, sequential tamoxifen-exemestane and extended tamoxifen-letrozole

This evaluation adapts a previous Canadian analysis of upfront and sequential adjuvant AI strategies in postmenopausal women with breast cancer to a Belgian perspective and includes an extended aromatase inhibitor (AI) strategy. A Markov model calculated monthly costs and outcomes in a hypothetical cohort of postmenopausal women with early-stage breast cancer. Baseline event rates and hazard ratios were derived from the Arimidex, Tamoxifen Alone or in Combination trial, International Exemestane Study and MA.17 trials. The analysis took a Belgian healthcare payer perspective with a 20-year time horizon. Costs and outcomes were discounted by 3%. Costs are in 2005 Euros. The cost-utility of all three strategies was favourable (<30,000 euros per QALY gained). Based on indirect comparisons using tamoxifen (TAM) alone as a common comparator, sequential TAM-AI was less costly and more effective than upfront or extended strategies. All three AI strategies were cost-effective alternatives to TAM alone, but sequential TAM-AI appears to be the economically preferred strategy.

The evolution of adjuvant endocrine therapy: Developments since St Gallen 2005

The most recent Oxford Overview analysis shows that tamoxifen remains a highly effective adjuvant endocrine therapy with continuing benefit for at least 15 years. The aromatase inhibitors (AIs) achieve a further small reduction in recurrence in postmenopausal women either as first-line treatment or sequentially after 2-3 years tamoxifen but so far usually without survival benefit. Differences in side effects are minor and specifically there is no evidence for significant differences in cardiovascular side effects. Extended adjuvant therapy with an AI after 5 years tamoxifen gives important additional protection to women with higher risk cancers. The relative benefits of first-line vs. sequential AIs after 2-3 years tamoxifen await the outcome of current trials. The major outstanding questions include duration of endocrine therapy, the value of ovarian suppression in premenopausal women in addition to other treatments, and the selection of patients who require endocrine therapy alone without additional chemotherapy.

The impact of cytochrome P450 2D6 metabolism in women receiving adjuvant tamoxifen

BACKGROUND

Tamoxifen is biotransformed to the potent anti-estrogen, endoxifen, by the cytochrome P450 (CYP) 2D6 enzyme. CYP2D6 genetic variation and inhibitors of the enzyme markedly reduce endoxifen plasma concentrations in tamoxifen-treated patients. Using a North Central Cancer Treatment Group adjuvant tamoxifen trial, we performed a comprehensive evaluation of CYP2D6 metabolism by assessing the combined effect of genetic variation and inhibition of the enzyme system on breast cancer recurrence and death.

METHODS

Medical records were reviewed at each randomizing site to determine whether CYP2D6 inhibitors were co-prescribed with tamoxifen. Extensive metabolizers were defined as patients without a *4 allele (i.e., wt/wt) who were not co-prescribed a CYP2D6 inhibitor. Patients with decreased CYP2D6 metabolism were classified as intermediate or poor metabolizers (PM) based on the presence of one or two CYP2D6*4 alleles or the co-administration of a moderate or potent CYP2D6 inhibitor. The association between CYP2D6 metabolism and clinical outcome was assessed using Cox modeling.

RESULTS

Medication history was available in 225/256 eligible patients and CYP2D6*4 genotype in 190 patients. Thirteen patients (6%) were co-prescribed a CYP2D6 inhibitor [potent (n = 3), moderate (n = 10)], resulting in the following CYP2D6 metabolism: extensive (n = 115) and decreased (n = 65). In the multivariate analysis, patients with decreased metabolism had significantly shorter time to recurrence (p = 0.034; adj HR = 1.91; 95% CI 1.05-3.45) and worse relapse-free survival (RFS) (p = 0.017; adj HR = 1.74; 1.10-2.74); relative to patients with extensive metabolism. Cox' modeling demonstrated that compared to extensive metabolizers, PM had the most significant risk of breast cancer relapse (HR 3.12, p = 0.007).

CONCLUSION

CYP2D6 metabolism, as measured by genetic variation and enzyme inhibition, is an independent predictor of breast cancer outcome in post-menopausal women receiving tamoxifen for early breast cancer. Determination of CYP2D6 genotype may be of value in selecting adjuvant hormonal therapy and it appears CYP2D6 inhibitors should be avoided in tamoxifen-treated women.

Cost-utility of adjuvant hormone therapies for breast cancer in post-menopausal women: sequential tamoxifen-exemestane and upfront anastrozole

BACKGROUND

Adjuvant Anastrozole (ANA) for 5 years and Tamoxifen followed by Exemestane (TAM-EXE) for 2.5 years each have become acceptable alternatives to 5 years of Tamoxifen (TAM) for post-menopausal women with breast cancer. As these newer options are associated with higher drug costs as well as improved outcomes, an economic evaluation was undertaken to compare the cost-utility of ANA and TAM-EXE relative to TAM alone and to each other in terms of cost per quality-adjusted life year (QALY) gained.

METHODS

A Markov model was developed to calculate monthly costs and outcomes in a hypothetical cohort of post-menopausal women with early-stage breast cancer. Baseline rates of cancer recurrence and adverse effects with TAM, and hazard ratios associated with ANA and EXE, were derived from the ATAC and IES trials. Patients received hormonal therapy for 5 years and benefit was modeled to persist 5 years beyond treatment. The analysis took a direct payer perspective with a 20-year time horizon. Costs and outcomes were discounted by 3%. Costs are in 2005 Canadian dollars.

RESULTS

ANA and TAM-EXE were associated with increased costs and QALYs, though the cost-utility of both relative to TAM alone was strongly favourable (<$50,000/QALY). Based on an indirect comparison of ANA and TAM-EXE, using TAM alone as a common comparator, the cost-utility of ANA relative to TAM-EXE appears unfavourable.

CONCLUSIONS

Both upfront and sequential AI options were cost-effective alternatives to TAM alone, but TAM-EXE appears to be the economically preferred AI option based on its more favourable cost-utility versus ANA.

Coronary heart disease and stroke with aromatase inhibitor, tamoxifen, and menopausal hormone therapy use

Results from the Women's Health Initiative randomized clinical trials of hormone therapy provide the clinical context for interpreting tamoxifen and aromatase inhibitor (AI) findings regarding coronary heart disease (CHD) and stroke. Of note is the potential link between increased stroke risk and increased dementia risk seen with the use of estrogen alone and the combination of estrogen/progestin. Like hormone therapy, tamoxifen has been found to generally lower low-density lipoprotein and total cholesterol but increase triglyceride levels. The preponderance of clinical evidence suggests that tamoxifen increases stroke risk and has no effect or modestly reduces CHD risk. Aromatase inhibitors generally do not influence low-density lipoprotein cholesterol and could modestly increase high-density lipoprotein cholesterol and reduce triglyceride levels. Current but limited evidence suggests that AIs have a modest increase or no effect on CHD as a class or as individual agents compared with tamoxifen. The influence of AIs on stroke is unsettled, and within-class differences might exist. In the adjuvant breast cancer setting, based on available evidence, the influence of AIs on CHD or stroke will infrequently influence overall patient outcome. If remaining issues are to be addressed, more rigorous CHD and stroke assessment procedures are needed in future trials evaluating AIs.