Fadrozole HCL (CGS-16949A) versus megestrol acetate treatment of postmenopausal patients with metastatic breast carcinoma: results of two randomized double blind controlled multiinstitutional trials

The implications of genetic variation for the pharmacokinetics and pharmacodynamics of aromatase inhibitors

INTRODUCTION

Breast cancer is the most common female cancer and remains a serious public health concern worldwide. Third-generation aromatase inhibitors (AIs) are widely used in postmenopausal women with estrogen receptor positive breast cancer. However, there is marked interindividual variability in terms of the efficacy and incidence of adverse events following treatment with AIs. Pharmacogenetics has the potential to predict clinical outcomes based on patients' genetic information, paving the way towards personalized treatment.

AREAS COVERED

This article reviews pharmacogenetic studies of AIs, including pharmacokinetic and pharmacodynamic aspects, highlighting those studies where the efficacy and adverse events of AIs have been examined using both candidate gene and genome-wide approaches.

EXPERT OPINION

Pharmacogenetics is a promising approach to develop personalized medicine with AIs. However, the application of pharmacogenetics to predict therapeutic efficacy and adverse events in breast cancer patients is still far from implementation in routine clinical practice. Large, comprehensive, multicenter studies that simultaneously evaluate multiple genes and pathways, including rare variants, are warranted in order to produce reliable and informative results. The ultimate aim is to develop clinically-relevant guidelines for breast cancer therapy.

Clinical utility of exemestane in the treatment of breast cancer

Breast cancer is the most prevalent cancer in women, causing a significant mortality worldwide. Different endocrine strategies are available for the treatment of hormone-sensitive breast cancer, including antiestrogen tamoxifen and fulvestrant, as well as third-generation aromatase inhibitors (AIs), such as letrozole, anastrozole, and exemestane. In this review, we will focus on exemestane, its clinical use, and its side effects. Exemestane is a steroidal third-generation AI now used in all treatment settings for breast cancer. In the metastatic disease, it has been extensively investigated as the first-, second-, and further-line treatment and it is now registered for the treatment of postmenopausal women with advanced estrogen-receptor-positive breast cancer whose disease has progressed following antiestrogen therapy. A potential lack of cross-resistance with nonsteroidal AIs has been described, giving additional therapeutic opportunities in sequences of endocrine agents. Exemestane is also approved for the adjuvant treatment of postmenopausal early breast cancer, either as upfront monotherapy for 5 years, as a switch following 2–3 years of tamoxifen, or as extended therapy beyond 5 years of adjuvant treatment. New promising data also showed a beneficial effect in young premenopausal early breast cancer patients, when administered together with ovarian suppression. Interesting results have also emerged when exemestane has been investigated as neodjuvant treatment as well as preventive agent in healthy women at high risk for breast cancer. Exemestane is generally well tolerated, with a side effect profile similar to that of other AIs, including menopausal symptoms, arthralgia, and bone loss. In conclusion, exemestane can be considered an effective and well-tolerated endocrine treatment option for all stages of breast cancer.

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.

Elevated plasma endoglin (CD105) predicts decreased response and survival in a metastatic breast cancer trial of hormone therapy

Background Endoglin (CD105) is a co-receptor for TGF-beta, is expressed by human vascular endothelial cells, and plays a major role in angiogenesis. Materials and methods Pretreatment EDTA plasma from 224 metastatic breast cancer patients enrolled in a phase III 2nd-line hormone therapy trial and 50 control subjects were assayed for endoglin using an ELISA. Results The female control group (n = 50) plasma endoglin upper limit of normal was defined as the mean + 2 SD (8.7 ng/ml). The breast cancer patient plasma endoglin was 6.40 +/- 2.23 ng/ml (range 3.00-19.79 ng/ml). Elevated plasma endoglin levels were detected in 26 of 224 patients (11.6%). Patients with elevated plasma endoglin had a reduced clinical benefit rate (CR + PR + Stable) (15 vs. 42%) (P = 0.01) to hormone therapy. TTP was shorter for patients with elevated plasma endoglin, but did not reach statistical significance (P = 0.2). Patients with elevated plasma endoglin had decreased overall survival (median 645 vs. 947 days) (P = 0.005). Conclusion Elevated pretreatment plasma endoglin levels predicted for decreased clinical benefit and a shorter overall survival in metastatic breast cancer patients treated with 2nd-line hormone therapy.

Efficacy and safety of aromatase inhibitors in early breast cancer

BACKGROUND

Third-generation aromatase inhibitors (AIs) are surfacing as the standard adjuvant treatment for postmenopausal women with hormone receptor positive breast cancer over tamoxifen but their long-term effects are still under investigation.

OBJECTIVE

In the light of current information, what factors should health practitioners take into consideration when prescribing AIs to patients?

METHODS

Results of several randomized controlled adjuvant clinical trials were reviewed to assess the efficacy of treatment and their subprotocols focusing on quality of life and skeletal health to highlight the safety concerns.

CONCLUSION

To prevent early recurrences, AIs should be considered as the upfront hormonal treatment of choice. They are also recommended for use as a switching strategy after 2-3 years of tamoxifen and as extended adjuvant treatment after 5 years of tamoxifen. The adverse events experienced are manageable and overall quality of life is not compromised; however, bone density must be monitored for patients at risk and appropriate bone-protection supplements need to be taken.

Aromatase inhibitors: past, present and future in breast cancer therapy

Estrogen has been implicated in promoting breast cancer in a majority of women. Endocrine therapy controlling estrogen production has been the guiding principle in treating breast cancer for more than a century. A greater understanding of this disease at a molecular level has led to the development of molecules that inhibit estrogen production by inhibiting the aromatase enzyme, that is the primary source of estrogen in postmenopausal women. This review examines the evolution of aromatase inhibitor (AI) based therapies over the past three decades. The third generation aromatase inhibitors (anastrozole, letrozole and exemestane), which have been found to be extremely specific and effective in an adjuvant/neoadjuvant/extended adjuvant setting are discussed from a biochemical and clinical perspective. A comprehensive discussion of the past, present, and future of aromatase inhibitors is conducted in this review.

Aromatase inhibitors in post-menopausal metastatic breast carcinoma

To summarise the advances in the hormonal treatment of post-menopausal metastatic breast cancer, this paper reviews the published literature regarding the randomised trials comparing aromatase inhibitors (AIs) versus tamoxifen as a first-line therapeutic choice, or AIs versus megestrole acetate (MEG) as a second-line option. The pooled analysis of these authors on AI versus MEG as a second-line option for post-menopausal metastatic breast cancer suggested that AIs do not add any significant benefit over MEG in terms of overall response rate (ORR) and time to progression. According to the Cochrane Database, use of an AI as a second-line therapy versus any other endocrine therapy (mostly MEG) has shown a significant benefit in terms of overall survival, but not for progression-free survival, clinical benefit (CB) or ORR. Concerning the authors' comparisons between AIs versus tamoxifen as a first-line endocrine option in post-menopausal women with metastatic breast carcinoma, AIs seem to be superior to tamoxifen, with a significant benefit in terms of ORR, CB and time to progression being observed in favour of AIs over tamoxifen with fixed effects estimates. According to the Cochrane Database, there was an advantage to the use of AIs over tamoxifen in terms of progression-free survival and CB, but not for overall survival or ORR. With regards to toxicity, AIs show similar levels of hot flushes and arthralgia, increased risks of nausea, diarrhoea and vomiting, but a decreased risk of vaginal bleeding and thromboembolic events compared with other endocrine therapies. Weight gain, dyspnoea and peripheral oedema seem to be more frequent with MEG. At present, there is no proved overall survival difference in patients who are treated first with an AI and then with tamoxifen compared with the opposite sequence. In the metastatic setting, results are limited and are based on retrospective analyses.

Elevated plasma tissue inhibitor of metalloproteinase-1 level predicts decreased response and survival in metastatic breast cancer

BACKGROUND

Tissue inhibitors of metalloproteinase (TIMPs) have at least 2 different functions. They inhibit the catalytic activity of matrix metalloproteinases, and they act as growth factors.

METHODS

Pretreatment ethylenediamine tetracetic acid plasma TIMP-1 was assayed from 251 patients who were enrolled in a Phase III, second-line, hormone therapy trial, and from a control group of 50 healthy, postmenopausal women by using the TIMP-1 enzyme-linked immunosorbent assay.

RESULTS

The plasma TIMP-1 levels from the postmenopausal control group (n = 50 women) were 201 +/- 86 ng/mL mean +/- standard deviation (range, 49-455 ng/mL). The upper limit of normal was defined as the mean +/- 2 standard deviations of the control group (373 ng/mL). Patient pretreatment plasma TIMP-1 levels ranged from 70 ng/mL to 982 ng/mL. Plasma TIMP-1 was elevated above the mean + 2 standard deviations of the control group (373 ng/mL) in 19 patients (7.6%). In univariate analysis, patients who had elevated versus normal plasma TIMP-1 levels had a reduced clinical benefit rate (CBR) (16% vs 42%; P = .03). The time to progression (TTP) (84 days vs 174 days; P < .0001) and overall survival (141 days vs 860 days; P = .0001) also were significantly shorter in patients who had elevated TIMP-1 levels. TTP and overall survival also were significantly shorter in patients who had higher TIMP-1 plasma levels when it was analyzed as a continuous variable. In multivariate analysis, elevated plasma TIMP-1 level remained a prognostic factor for reduced overall survival (P < .0001) along with elevated serum HER-2/neu (P < .0001) and the presence of visceral metastases (P = .008).

CONCLUSIONS

Elevated pretreatment plasma levels of TIMP-1 predicted a decreased response to second-line hormone therapy and reduced survival in women with metastatic breast cancer.

Aromatase inhibitors for treatment of advanced breast cancer in postmenopausal women

BACKGROUND

Hormonal treatments for advanced or metastatic breast cancer, such as tamoxifen and the progestins megestrol acetate and medroxyprogesterone acetate, have been in use for many years. Aromatase inhibitors (AIs) are a class of compounds that systemically inhibit oestrogen synthesis in the peripheral tissues. Aminoglutethimide was the first AI in clinical use (first generation) and had a similar tumour-regressing effect to other endocrine treatments, which showed the potential of this alternative type of therapy. Other AIs have since been developed and the third generation AIs anastrozole, exemestane and letrozole are in current use. Randomised evidence on response rates and side effects of these drugs is still limited.

OBJECTIVES

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

SEARCH STRATEGY

The Cochrane Breast Cancer Group Specialised Register was searched on 3 December 2004 using the codes for "advanced" and "endocrine therapy". Details of the search strategy applied to create the Register and the procedure used to code references are described in the Cochrane Breast Cancer Group module on The Cochrane Library. The search was updated to 30 September 2005 and additional publications were included. Experts were consulted to determine that no relevant studies had been excluded.

SELECTION CRITERIA

Randomised trials comparing the effects of any aromatase inhibitor versus other endocrine therapy, no endocrine therapy or a different aromatase inhibitor in the treatment of advanced (metastatic) breast cancer.

DATA COLLECTION AND ANALYSIS

Data from published trials were extracted by two independent review authors. A third independent author then carried out a further cross check for accuracy and consistency. Hazard ratios (HR) were derived for analysis of time-to-event outcomes (overall and progression-free). Odds ratios (OR) were derived for objective response and clinical benefit (both analysed as dichotomous variables). Toxicity data were extracted where present and treatments were compared using odds ratios. All but one of the studies included data on one or more of the following outcomes: overall survival, progression-free survival, clinical benefit and objective response.

MAIN RESULTS

Thirty studies were identified, twenty five of which were included in the main analysis of any AI versus any other treatment (9416 women). The pooled estimate showed a significant survival benefit for treatment with an AI over other endocrine therapies (HR 0.89, 95%CI 0.82 to 0.96). 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). The results for progression-free survival, clinical benefit and objective response were not statistically significant and there was statistically significant heterogeneity across types of AI. There were very limited data to compare one AI with a different AI, but these suggested an advantage for letrozole over anastrozole. All the trials of AIs used exclusively as first-line therapy were against tamoxifen. There was an advantage to treatment with AIs in terms of progression-free survival (HR 0.78, 95% CI 0.70 to 0.86) and clinical benefit (OR 0.70, 95% CI 0.51 to 0.97) but not overall survival or objective response. There was considerable heterogeneity across studies when considering clinical benefit (P = 0.001). Use of an AI as second-line therapy showed a significant benefit in terms of overall survival (HR 0.80, 95% CI 0.66 to 0.96) but not for progression-free survival (HR 1.08, 95% CI 0.89 to 1.31), clinical benefit (OR 1.00, 95% CI 0.87 to 1.14) or objective response (OR 0.96, 95% CI 0.81 to 1.14). This is difficult to interpret due to the extreme heterogeneity across AIs for progression-free survival but not the other endpoints.AIs have a different toxicity profile to other endocrine therapies. For all AIs combined, they had similar levels of hot flushes (especially when compared to tamoxifen) and arthralgia, increased risks of nausea, diarrhoea and vomiting, but a decreased risk of vaginal bleeding and thromboembolic events compared with other endocrine therapies. A similar pattern of risks and benefits was still seen when analyses were limited to the currently most-prescribed third generation AIs.

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.

Survival with aromatase inhibitors and inactivators versus standard hormonal therapy in advanced breast cancer: meta-analysis

BACKGROUND

Aromatase inhibitors and inactivators have been extensively tested in patients with advanced breast cancer, but it is unclear whether they offer any survival benefits compared with standard hormonal treatment with tamoxifen or progestagens. We performed a meta-analysis of randomized controlled trials that compared several generations of aromatase inhibitors and inactivators with standard hormonal treatment in patients with advanced breast cancer.

METHODS

The endpoint that we assessed was survival. Trials were located through searches of PubMed and Cochrane Library (last update March 2006). Relative hazards (RHs) were summarized across trials through fixed- and random-effects analyses, and heterogeneity was assessed with the Q and I2 statistics. All statistical tests were two-sided.

RESULTS

Twenty-five different comparisons, with a total of 8504 patients, were included in the meta-analysis. We found statistically significant survival benefits with third-generation aromatase inhibitors and inactivators (vorozole, letrozole, examestane, and anastrazole) (RH = 0.87, 95% confidence interval [CI] = 0.82 to 0.93; P<.001) but not with first-generation (aminoglutethimide) or second-generation (formestane and fadrozole) agents. The difference in the summary effects between these two groups of trials was statistically significant (P = .04). The survival benefit with third-generation agents in first-line trials, in which these agents were compared with tamoxifen (11% RH reduction, 95% CI = 1% to 19%; P = .03), was identical to their benefit in second- and subsequent-line trials in which these agents were compared with other treatments (14% RH reduction, 95% CI = 6% to 21%; P<.001).

CONCLUSIONS

Inhibition of the aromatase system, in particular with third-generation aromatase inhibitors and inactivators, appears to be associated with statistically significant improved survival of patients with advanced breast cancer compared with standard hormonal treatments.

Second consensus on medical treatment of metastatic breast cancer

The present consensus manuscript defines evidence-based recommendations for state-of-the-art treatment of metastatic breast cancer depending on disease-associated and biologic variables.

New aromatase inhibitors as second-line endocrine therapy in postmenopausal patients with metastatic breast carcinoma: a pooled analysis of the randomized trials

BACKGROUND

New aromatase inhibitors (AI) (second-generation: formestane and fadrozole; third-generation: letrozole, anastrozole, vorozole, and exemestane) have been tested in several controlled clinical trials after tamoxifen failure in metastatic breast carcinoma (MBC). They have resulted in better survival compared with megestrol acetate (MEG) in a number of studies. The authors performed a pooled analysis including all the Phase III trials published between 1996 and 2004 evaluating the AIs approved or not by the Food and Drug Administration (FDA) and the European Agency for the Evaluation of Medical Products (EMEA) as second-line endocrine therapy (ET) for patients with MBC.

METHODS

The overall response rate (ORR) and time to disease progression (TTP) were considered the primary end points, whereas toxicity was regarded as a secondary objective. Relative risk, 95% confidence interval, and heterogeneity were derived using 2 methods.

RESULTS

No significant differences in ORR and TTP were noted in the entire group of 9 trials comparing AI with MEG (3908 patients) and in the 6 trials comparing nonsteroidal AI and MEG (2415 patients). AI yielded significantly more hot flashes than MEG (P = 0.004) but caused significantly less toxicity than MEG in weight gain (P = 0.001), dyspnea (P = 0.008), and peripheral edema (P = 0.03). Significant heterogeneity for nausea, weight gain, dyspnea, and peripheral edema was registered. When steroidal AIs were excluded from the toxicity analysis, nausea maintained its strongly significant heterogeneity (P = 0.0002), whereas weight gain, dyspnea, and peripheral edema lost their significance.

CONCLUSIONS

This pooled analysis suggested that AIs in second-line ET for patients with MBC do not seem to add any significant benefit to MEG in terms of ORR and TTP. With regard to toxicity, the findings in the current study showed that weight gain, dyspnea, and peripheral edema are more frequent with the use of MEG, whereas hot flashes were more represented using AI.

Aromatase inhibition: translation into a successful therapeutic approach

The development of the novel third-generation aromatase inhibitors and inactivators for breast cancer treatment is one of the most successful contemporary achievements in cancer therapy. Parallel to studies evaluating toxicity and clinical efficacy in metastatic disease, the endocrine effects of multiple compounds were evaluated, leading to the identification of the highly potent third-generation aromatase inhibitors based on estrogen deprivation and aromatase inhibition in vivo. Thus, translational studies have been of vital importance identifying the unique characteristics of these compounds. Whereas first- and second-generation aromatase inhibitors inhibit estrogen synthesis in vivo by up to 90%, the third-generation compounds anastrozole, exemestane, and letrozole were found to cause > or =98% aromatase inhibition. This article summarizes and discusses the "translational research" that provided the background for the implementation of the third-generation aromatase inhibitors and inactivators into large clinical trials. The need for future translational research exploiting the mechanisms of resistance to these compounds for future improvement of endocrine therapy is emphasized.

The therapeutic potential of novel aromatase inhibitors in breast cancer

For over 20 years, aromatase inhibitors have played a role in the treatment of breast cancer. However, until relatively recently, their utility has been limited by a lack of selectivity and significant toxicity. Several second and third generation aromatase inhibitors which are highly selective for the aromatase enzyme have reached clinical trials this decade. As a result of these initial studies, aromatase inhibitors are now established as second line agents in the treatment of postmenopausal women with advanced breast cancer. They are now under evaluation in several other settings, including adjuvant and neoadjuvant therapy, and as part of combination treatment in premenopausal women. This review focuses on recent and ongoing clinical trials and the effect these have had on the clinical use of aromatase inhibitors.

Aromatase inhibitors and other novel agents in breast cancer treatment

Thirty years after the introduction of tamoxifen, which was expanded from palliation of metastatic cancer to recent application for chemoprevention, the primacy of this drug as the mainline pharmacological intervention is currently being challenged by the third generation aromatase inhibitors and inactivators. In contrast to the oestrogen receptor blockade provided by tamoxifen, aromatase inhibitors result in deprivation of oestrogens in postmenopausal women both through paracrine/intracrine and endocrine modulation. Experimental evidence has shown a significant (97-99%) reduction of in vivo aromatase activity and an equal or sometimes better antitumour activity compared with megestrol acetate when these drugs are used as second-line treatment for metastatic breast cancer. Recent pivotal studies in first-line settings comparing tamoxifen for metastatic breast cancer and preliminary results from the neoadjuvant trials demonstrate that third generation aromatase inhibitors are superior to tamoxifen. With a better understanding of local tissue production of oestrogen through oestrone sulfatase, which hydrolyses oestrone sulfate to oestrone, and 17-beta-hydroxysteroid dehydrogenase Type 1, which in turn catalyses the reduction of oestrone to oestradiol, more powerful tactics for oestrogen starvation of cancer may be realised in future.

Role of aromatase inhibitors in the treatment of breast cancer

BACKGROUND

Estrogens play a pivotal role in the development of breast cancer. Endocrine therapy based on estrogen blockade is a well-established treatment in hormone-dependent breast cancer. Tamoxifen citrate has long been considered the "gold standard" due to its relative safety and efficacy. Aromatase inhibitors are anti-estrogen agents that target specifically the aromatase enzyme, which is the final step in the estrogen production. The first use of aromatase inhibitors in breast cancer was associated with adverse effects such as rash, drowsiness, and adrenal-gland suppression. Newer third-generation agents are emerging as potential alternatives to tamoxifen, associating clinical efficacy with a more favorable safety profile.

OBJECTIVES

The aim of this article is to review the mechanisms of actions pharmacology, adverse effects, and clinical applications of the aromatase inhibitors available in the United States.

METHODS

The terms breast cancer or neoplasia, aromatase, aromatase inhibitors, third-generation, endocrine therapy, and antiestrogens were used to search MEDLINE for English-language studies published between 1966 and April 2004. A parallel search was performed at the corresponding Web site of each of the aromatase inhibitors available in the United States. Identified publications relevant to the article objectives were selected.

RESULTS

Anastrozole, letrozole, and exemestane are the 3 commercially available aromatase inhibitors approved by the US Food and Drug Administration for the treatment of hormone receptor-positive breast cancer in postmenopausal women. They have been used in several clinical scenarios, including advanced and early disease and chemoprevention, and in the neoadjuvant setting. There is evidence that aromatase inhibitors are more effective and tolerable than tamoxifen in advanced breast cancer and in the neoadjuvant setting. Based on the results of a large, randomized trial, their use in early disease and in chemoprevention is also promising. Aromatase inhibitors appear safe; however, the long-term safety profile is still unknown, especially concerning bone metabolism.

CONCLUSION

Third-generation aromatase inhibitors are a new treatment modality in estrogen and/or progesterone-receptor positive breast cancer. Although they are replacing the "classic" antiestrogen agents used in metastatic breast cancer, their benefit in early disease and as chemopreventive agents is not completely clear. Ongoing clinical studies should become available within the next few years and will provide additional recommendations for their use in patients with breast cancer.

Baseline serum NTx levels are prognostic in metastatic breast cancer patients with bone-only metastasis

BACKGROUND

There is significant heterogeneity in survival of patients with metastatic breast cancer who have bone-only metastasis. We studied the correlation of serum N-telopeptide (NTx), a marker of bone resorption, and its correlation with clinical outcomes in patients with metastatic breast cancer with bone-only or bone plus soft tissue metastasis.

PATIENTS AND METHODS

Serum was taken from 250 metastatic breast cancer patients with bone-only or bone plus soft tissue metastasis who participated in two similar randomized studies of second-line hormone therapy. An enzyme-linked immunosorbent assay specific for NTx of type I bone collagen was used to detect serum levels.

RESULTS

Sixty patients (24%) had elevated serum NTx levels, using the mean + 2 standard deviations (26 nanomoles Bone Collagen Equivalents per liter) of healthy women as a cut-off. The median duration of clinical benefit was significantly shorter in the group with elevated serum NTx levels compared with the group that had normal serum NTx levels (P=0.0004). Time to progression (TTP) was also significantly shorter in the patients with elevated serum NTx at 139 days compared with 220 days (P=0.0006). Median survival was also significantly shorter in patients with elevated baseline serum NTx levels at 663 days compared with 941 days (P<0.0001).

CONCLUSION

In this study, breast cancer patients with bone-only or bone plus soft tissue metastasis and elevated serum NTx levels have a shorter duration of clinical benefit, TTP and overall survival.

Aromatase inhibition in the treatment of advanced breast cancer: is there a relationship between potency and clinical efficacy?

Two-thirds of breast tumours are oestrogen-receptor positive and 60-70% of these tumours respond to interventions that reduce the effects of oestrogen. Until recently, tamoxifen was the drug of choice for the treatment of hormone-responsive early and advanced breast cancer. However, tamoxifen is associated with increased incidences of endometrial cancer and thromboembolic disease, and many tumours eventually become resistant to treatment with tamoxifen. Thus, there is a need for alternative therapies with different mechanisms of action. In postmenopausal women, aromatase inhibitors (AIs) suppress oestrogen levels by inhibiting oestrogen synthesis via the aromatase enzyme pathway. The third-generation AIs (anastrozole, letrozole and exemestane) are more potent than the earlier AIs (aminoglutethimide, formestane and fadrozole) with respect to both aromatase inhibition and oestrogen suppression. While the earlier AIs were unable to show any benefit over megestrol acetate or tamoxifen as second- and first-line therapy, respectively, in postmenopausal women with advanced breast cancer, third-generation AIs have shown significant benefits in both settings. Comparison of aromatase inhibition and oestrogen suppression between the third-generation AIs anastrozole and letrozole showed a small but significantly greater difference in the degree of suppression of oestrone and oestrone sulphate (but not oestradiol), with letrozole. In an open-label trial, there were no significant differences between letrozole and anastrozole for the clinical end points of time to progression (primary end point), time to treatment failure, overall survival, clinical benefit, duration of clinical benefit, time to response, duration of response or objective response rate in patients with confirmed hormone receptor-positive tumours. Together these data suggest that once a certain threshold of aromatase inhibition is reached, small differences in oestrogen suppression between the third-generation AIs do not lead to clinically significant differences in overall efficacy.

Oestrogen suppression--lessons from clinical studies

In few, if any, areas of cancer research has "translational research" played a role such as the one it has played in the development of endocrine therapy. Thus, much of the understanding of the mechanisms of action of different therapies has been achieved by developing novel hypotheses based on clinical observations. Ovarian ablation was developed as an empirical therapy long before characterization of oestrogen disposition or detection of the oestrogen receptor. The first-generation aromatase inhibitor, aminoglutethimide, was implemented as a strategy to achieve a 'medical adrenalectomy' and was discovered as an aromatase inhibitor subsequent to clinical observations. Currently, observations such as the lack of cross-resistance between aromatase inhibitors and inactivators and the diverse effects from combined therapy using tamoxifen in concert with hormonal suppression in pre- and post-menopausals are provoking interesting questions for further research.

Comparison between aromatase inhibitors and sequential use

The biochemical efficacy of aromatase inhibitors and inactivators in vivo may be determined by two types of methods; by measuring plasma or tissue estrogen levels, or assessment of the conversion of the androgen substrate (in practice, androstenedione) into estrogens (estrone) by the use of tracer methods. While methods to determine plasma and tissue estrogens are limited through lack of sensitivity required to measure the very low concentrations recorded in postmenopausal women on treatment with these compounds, measurement of in vivo aromatization is an extensive procedure, applicable to a limited number of patients only. While we may correlate the mean level of aromatase inhibition achieved with different compounds to clinical efficacy, data correlating individual estrogen suppression to clinical outcome among patients treated with a specific compound is limited. The now well-characterized phenomenon of lack of cross-resistance between non-steroidal aromatase inhibitors and steroidal aromatase inactivators are likely due to biochemical effects not related to differences in total body aromatase inhibition.

Aromatase inhibitors versus tamoxifen for management of postmenopausal breast cancer in the advanced disease and neoadjuvant settings

The third-generation aromatase inhibitors anastrozole, exemestane and letrozole have become firmly established as the agents of choice in patients with tamoxifen-resistant tumors. Large, well-conducted, double-blind clinical trials directly comparing the non-steroidal aromatase inhibitors anastrozole and letrozole with tamoxifen in the advanced disease setting have matured. Based on these trials, there is sufficient evidence to choose one of these agents over tamoxifen because of a superior time to disease progression and acceptable toxicity which includes a lower incidence of thromboembolic complications. Information for the steroidal aromatase inhibitor exemestane will be forthcoming from a phase III trial which has completed accrual. Consistent with the findings in the advanced disease setting, a double-blind trial comparing letrozole with tamoxifen in the neoadjuvant setting revealed superiority for letrozole in terms of clinical response rate. This provides a strong impetus for further study of the aromatase inhibitors in the preoperative setting.

Anastrozole versus tamoxifen as first-line therapy in postmenopausal patients with hormone-dependent advanced breast cancer: a prospective, randomized, phase III study

A prospective phase III trial comparing anastrozole with tamoxifen as first-line therapy in postmenopausal, hormone-dependent, advanced breast cancer (ABC). Patients were randomized to anastrozole 1 mg daily (n = 121) or tamoxifen 40 mg daily (n = 117). Efficacy and tolerability were evaluated after 3 months' therapy, and survival was evaluated at median time of follow-up. At a median follow-up of 13.3 months, clinical benefit (CB) was achieved in 83% and 56% of anastrozole and tamoxifen patients, respectively (p < 0.001); median time to disease progression (TTP) in patients achieving CB was 18.0 months and 7.0 months, respectively, (hazard ratio [HR] = 0.13, 95% CI = 0.08-0.20, p < 0.01). At data cutoff, 89% of tamoxifen patients had died, compared with 60% of anastrozole patients; median time to death was 17.4 months and 16.0 months, respectively (HR = 0.64, 95% CI = 0.47-0.86, p = 0.003). Therapy was well tolerated in both groups. Anastrozole showed significant advantages over tamoxifen for CB, median TTP in patients gaining CB, and survival. These data further support routine use of anastrozole as first-line treatment for postmenopausal hormone-dependent ABC.

Endocrine and intracrine sources of androgens in women: inhibition of breast cancer and other roles of androgens and their precursor dehydroepiandrosterone

Serum androgens as well as their precursors and metabolites decrease from the age of 30-40 yr in women, thus suggesting that a more physiological hormone replacement therapy at menopause should contain an androgenic compound. It is important to consider, however, that most of the androgens in women, especially after menopause, are synthesized in peripheral intracrine tissues from the inactive precursors dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) of adrenal origin. Much progress in this new area of endocrine physiology called intracrinology has followed the cloning and characterization of most of the enzymes responsible for the transformation of DHEA and DHEA-S into androgens and estrogens in peripheral target tissues, where the locally produced sex steroids are exerting their action in the same cells in which their synthesis takes place without significant diffusion into the circulation, thus seriously limiting the interpretation of serum levels of active sex steroids. The sex steroids made in peripheral tissues are then inactivated locally into more water-soluble compounds that diffuse into the general circulation where they can be measured. In a series of animal models, androgens and DHEA have been found to inhibit breast cancer development and growth and to stimulate bone formation. In clinical studies, DHEA has been found to increase bone mineral density and to stimulate vaginal maturation without affecting the endometrium, while improving well-being and libido with no significant side effects. The advantage of DHEA over other androgenic compounds is that DHEA, at physiological doses, is converted into androgens and/or estrogens only in the specific intracrine target tissues that possess the appropriate physiological enzymatic machinery, thus limiting the action of the sex steroids to those tissues possessing the tissue-specific profile of expression of the genes responsible for their formation, while leaving the other tissues unaffected and thus minimizing the potential side effects observed with androgens or estrogens administered systemically.

Double-blind randomised trial comparing the non-steroidal aromatase inhibitors letrozole and fadrozole in postmenopausal women with advanced breast cancer

BACKGROUND

To compare the efficacy, safety and tolerability of letrozole, an advanced non-steroidal aromatase inhibitor, and fadrozole hydrochloride, an older-generation drug in this class, we conducted a randomised double-blind trial in postmenopausal women with advanced breast cancer.

PATIENTS AND METHODS

One hundred and fifty-seven postmenopausal women with advanced breast cancer were enrolled and randomly assigned to receive letrozole or fadrozole in a multicentre, randomised double-blind trial in Japan. One hundred and fifty-four eligible patients were treated with either letrozole 1.0 mg once daily (n = 77) or fadrozole 1.0 mg twice daily (n = 77), for a minimum of 8 weeks.

RESULTS

Letrozole showed a significantly higher overall objective response rate [complete response (CR) + partial response (PR)] than fadrozole (31.2% and 13.0%, respectively; P = 0.011, Fisher's exact test). Clinical benefits defined as CR, PR and stable disease (no change in status for more than 24 weeks) were also higher in patients treated with letrozole (50.6%) than fadrozole (35.1%). Letrozole was significantly superior to fadrozole in terms of the dominant lesion in soft tissue, bone and viscera (P = 0.011, stratified Mantel-Haenszel test). Median time to progression was 211 days in the letrozole group and 113 days in the fadrozole group with no significant difference (P = 0.175, log-rank test). Letrozole markedly reduced the estradiol, estrone and estrone sulfate levels in peripheral blood within 4 weeks. The suppressive effect of fadrozole on these hormone levels was insufficient. Adverse drug reactions were observed in 35.9% of the patients treated with letrozole and in 39.5% of those treated with fadrozole with no significant difference between the two groups (P = 0.74, Fisher's exact test). Most of the adverse drug reactions were rated as grade 1 or 2.

CONCLUSIONS

The results show letrozole at a dose of 1.0 mg once daily to be more effective in treating postmenopausal women with advanced breast cancer than fadrozole at 1.0 mg twice daily, with similar safety and tolerability profiles.

Efficacy and economics of hormonal therapies for advanced breast cancer

Breast cancer is a leading cause of cancer-related mortality among postmenopausal women in the US, and the economic burden of breast cancer care comprises a large percentage of the healthcare budget. Hormonal therapies have a proven place in the management of advanced breast cancer. This type of therapy is more likely to be used in older, compared with younger, women, because tumours in older women are more likely to express estrogen and progesterone receptors. While it is difficult to measure the costs of cancer care because of variation in extent and duration of treatment, treatment-related costs including costs of hormonal agents used for advanced disease account for a relatively small component of the overall costs. Newer hormonal regimens such as the new third generation nonsteroidal (letrozole, anastrozole) and steroidal (exemestane) aromatase inhibitors have shown improved clinical efficacy compared with standard regimens such as megestrol and tamoxifen in the metastatic setting in terms of objective responses or time to tumour progression. In addition the newer agents have improved toxicity profiles. Cost analyses of the newer aromatase inhibitors (anastrozole and letrozole), compared with megestrol, show an optimistic outlook for these agents. Additional work needs to be done looking at a comparison of the efficacy and costs of the aromatase inhibitors relative to the currently recommended hormonal treatments used for women with metastatic breast cancer.

Aromatase inhibitors and inactivators for breast cancer therapy

Aromatase inhibitors and inactivators are increasingly important to the therapy of advanced breast cancer in postmenopausal women. These compounds are also currently being evaluated in the adjuvant setting and may have potential in breast cancer prevention. In addition to the recent clinical results, experimental research with development of aromatase 'knockout' mice as well as certain clinical observations in individuals lacking this enzyme have deepened our understanding of estrogens outside of the field of reproduction. Such information should help us to further develop this type of therapy in breast cancer and, in particular, extend our understanding of the lack of complete cross-resistance between aromatase inhibitors and inactivators. Clinically, third-generation aromatase inhibitors and inactivators have shown superiority compared with conventional treatment in advanced postmenopausal breast cancer with respect to second-line (tamoxifen failures) as well as first-line therapy. The fact that tamoxifen is noncurative in metastatic disease but improves long-term survival in the adjuvant setting suggests that even modest improvements in therapy of advanced disease may be translated into survival benefits in patients with early disease. In addition, these novel compounds with lack of complete cross-resistance extend the scope of using sequential treatment options to maximise the duration of optimal endocrine therapy in metastatic breast cancer disease.

Tamoxifen resistant and refractory breast cancer: the value of aromatase inhibitors

Tamoxifen has dominated endocrine treatment of breast cancer for over two decades. It is useful in metastatic breast cancer, adjuvant therapy, preoperative treatment, ductal carcinoma-in-situ and chemoprevention. However, breast cancer may be refractory to tamoxifen or develop resistance to it with ongoing treatment. This resistance involves several mechanisms including receptor mutation causing 'estrogen hypersensitivity' and an increasing agonist effect of tamoxifen. Megestrol (megestrol acetate), in North America, and aminoglutethimide, in Europe, have been the traditional second line therapies after tamoxifen in advanced breast cancer. Aromatase (estrogen synthetase) inhibitors are a logical alternative to tamoxifen to antagonise the effects of estrogen on breast cancer. The third-generation non-steroidal aromatase inhibitors anastrozole, letrozole and vorozole, and the steroidal inhibitor exemestane, have been studied after tamoxifen versus either megestrol or aminoglutethimide. They showed enhanced efficacy and significantly superior toxicity profiles. Compliance with the inhibitors was also significantly better than with the traditional treatments. Aromatase inhibitors have most recently been shown to be superior to tamoxifen as initial therapy and are being extensively tested in the adjuvant setting after, or instead of, tamoxifen. Pilot studies of chemoprevention are also being undertaken. The aromatase inhibitors are an important new addition to the armamentarium of breast cancer therapy.

Antiaromatase agents: evolving role in adjuvant therapy

The goal of adjuvant hormonal therapy is to prevent breast cancer recurrence. Standard therapy with tamoxifen has shown great value in the adjuvant setting; however, its tolerability profile can render it unsuitable for some patients. The aromatase inactivator, exemestane, and the 2 aromatase inhibitors, letrozole and anastrozole, have been shown to be equivalent or superior to tamoxifen with respect to multiple endpoints in patients with metastatic breast cancer. With tolerability profiles that are similar to, and in many cases, more acceptable than that of tamoxifen, and efficacy potentially superior to tamoxifen, studies using the antiaromatase agents as adjuvant therapy are currently ongoing. These trials will answer some important questions, such as the order in which adjuvant hormonal therapies are selected to maximize efficacy, whether the antiaromatase agents show improved tolerability, and whether combination therapy is more effective than monotherapy.

A summary of second-line randomized studies of aromatase inhibitors

The new generation of selective aromatase inhibitors (anastrozole, letrozole and exemestane) offer a significant efficacy and safety advantage over both older agents in this class (aminoglutethimide) and the progestins (megestrol acetate (MA)), as second-line treatment for postmenopausal women with advanced hormone-dependent breast cancer who have failed on tamoxifen therapy. Exemestane, a steroidal aromatase inhibitor, has been shown to have activity after failure with the non-steroidal aromatase inhibitors, anastrozole and letrozole, and could be used as third-line treatment. Although the newer aromatase inhibitors belong to the same class and appear, from indirect comparisons, to have similar efficacy compared with the older therapies, they have different pharmacokinetic and pharmacodynamic profiles, suggesting the potential for clinical differences. Compared with exemestane and letrozole, anastrozole shows greater selectivity for aromatase, as it lacks any evidence of an effect on adrenal steroidogenesis and has no androgenic effects. Therefore, it is clear that these agents should not be considered to be similar in all respects. In summary, the introduction of the aromatase inhibitors represents a significant step forward in the treatment of advanced breast cancer in postmenopausal women. Studies in the adjuvant setting will ultimately determine whether the differences in pharmacokinetics and phamacodynamics will be of clinical relevance.

DHEA and its transformation into androgens and estrogens in peripheral target tissues: intracrinology

A new understanding of the endocrinology of menopause is that women, at menopause, are not only lacking estrogens resulting from cessation of ovarian activity but have also been progressively deprived for a few years of androgens and some estrogens originating from adrenal DHEA and androstenedione (4-dione). In fact, serum DHEA decreases by about 60% between the maximal levels seen at 30 years of age to the age of menopause. This decreased secretion of DHEA and DHEA-S by the adrenals is responsible for a parallel decrease in androgen and estrogen formation in peripheral tissues by the steroidogenic enzymes specifically expressed in each cell type in individual target tissues. This new field of endocrinology, called intracrinology, describes the local synthesis of androgens and estrogens made locally in each cell of each peripheral tissue from the adrenal precursors DHEA and 4-dione. These androgens and estrogens exert their action in the same cells where their synthesis takes place and they are released from these target cells only after being inactivated. To further understand the effect of DHEA in women, DHEA has been administered in postmenopausal women for 12 months. Such treatment resulted in increased bone formation and higher bone mineral density accompanied by elevated levels of osteocalcin, a marker of bone formation. Vaginal maturation was stimulated, while no effect was observed on the endometrium. Preclinical studies, on the other hand, have shown that, due to its predominant conversion into androgens, DHEA prevents the development and inhibits the growth of dimethylbenz(a)anthracene-induced mammary carcinoma in the rat, a model of breast cancer. DHEA also inhibits the growth of human breast cancer ZR-75-1 xenografts in nude mice. The inhibitory effect of DHEA on breast cancer is due to an androgenic effect of testosterone and dihydrotestosterone made locally from DHEA. When used as replacement therapy, DHEA is free of the potential risk of breast and uterine cancer, while it stimulates bone formation and vaginal maturation and decreases insulin resistance. The combination of DHEA with a fourth generation SERM, such as EM-652 (SCH 57068), a compound having pure and potent antiestrogenic activity in the mammary gland and endometrium, could provide major benefits for women at menopause (inhibition of bone loss and serum cholesterol levels) with the associated major advantages of preventing breast and uterine cancer. A widely used application of intracrinology is the treatment of prostate cancer where the testicles are blocked by an LHRH agonist while the androgens made locally in the prostate from DHEA are blocked by a pure antiandrogen. Such treatment, called combined androgen blockade, has led to the first demonstration of a prolongation of life in prostate cancer.

Biologic basis and evolving role of aromatase inhibitors in the management of invasive carcinoma of the breast

BACKGROUND AND OBJECTIVES

The most powerful predictor of the response of breast cancers to hormonal therapy is the presence of estrogen receptors in the tumor cells. Estrogen receptors are expressed in approximately 35-55% of all breast tumors but up to 80-90% of tumors from women older than 55 years.

METHODS

At this time, tamoxifen remains the first-line hormonal therapy for breast cancer of all stages. However, the aromatase inhibitors are evolving into an important treatment option. Aromatase inhibitors prevent the conversion of precursors (androgens) to estrogens.

RESULTS

On the basis of several randomized clinical trials, aromatase inhibitors have become established as the second-line therapy for postmenopausal women with advanced breast cancer progressing during tamoxifen therapy. Furthermore, very recent trials support the use of these agents as first-line therapy in place of tamoxifen.

CONCLUSIONS

The roles of the selective aromatase inhibitors in the prevention of breast cancer and in the neoadjuvant and adjuvant treatment of early-stage breast cancer are the focus of several planned and ongoing large-scale clinical trials. These trials will answer some of the many questions that remain regarding optimal hormonal therapy for hormone-dependent breast cancer.

Aromatase inhibitors for breast cancer: pharmacoeconomic considerations

Although the anti-oestrogen tamoxifen is recognised as the treatment of choice for both premenopausal and postmenopausal women with advanced hormone-dependent breast cancer, oestrogen deprivation can also be achieved, with apparently less adverse-effects, through selective inhibition of aromatase. Recent clinical trials have demonstrated the efficacy and tolerability of the new generation of aromatase inhibitors as second-line and first-line therapy in postmenopausal women with breast cancers who were eligible for endocrine treatment. Speculating that administration of aromatase inhibitors will not be limited to postmenopausal breast cancer, a pharmacoeconomic perspective is considered based on available data and putative therapeutic application during various phases of the disease.

Aromatase inhibitors in the treatment and prevention of breast cancer

PURPOSE

The purpose of this article is to provide an overview of the current clinical status and possible future applications of aromatase inhibitors in breast cancer.

METHODS

A review of the literature on the third-generation aromatase inhibitors was conducted. Some data that have been presented but not published are included. In addition, the designs of ongoing trials with aromatase inhibitors are outlined and the implications of possible results discussed.

RESULTS

All of the third-generation oral aromatase inhibitors--letrozole, anastrozole, and vorozole (nonsteroidal, type II) and exemestane (steroidal, type I)--have now been tested in phase III trials as second-line treatment of postmenopausal hormone-dependent breast cancer. They have shown clear superiority compared with the conventional therapies and are therefore considered established second-line hormonal agents. Currently, they are being tested as first-line therapy in the metastatic, adjuvant, and neoadjuvant settings. Preliminary results suggest that the inhibitors might displace tamoxifen as first-line treatment, but further studies are needed to determine this.

CONCLUSION

The role of aromatase inhibitors in premenopausal breast cancer and in combination with chemotherapy and other anticancer treatments are areas of future exploration. The ongoing adjuvant trials will provide important data on the long-term safety of aromatase inhibitors, which will help to determine their suitability for use as chemopreventives in healthy women at risk of developing breast cancer.

Crucial role of cytokines in sex steroid formation in normal and tumoral tissues

There is evidence suggesting that local intracrine formation of sex steroids from inactive precursors, dehydroepiandrosterone (DHEA), its sulfate (DHEA-S) and 4-androstenedione (4-DIONE) plays an important role in the regulation of growth and function of peripheral target tissues. Moreover, human solid tumors are often infiltrated by stromal/immune cells secreting a wide spectra of cytokines. These cytokines might in turn regulate the activity of both immune and neoplastic cells. Our data demonstrate that the potent regulatory effects of interleukin-4 (IL-4) and IL-6 on both estrogenic and androgenic 17beta-HSD/KSR activities in breast cancer cells depend on the cell-specific gene expression of various types of 17beta-HSD/KSR enzymes. However, in both estrogen-receptor (ER)-positive (ZR-75-1, T-47D) and ER-negative (MDA-MB-231, BT-20) human breast cancer cells, exposure to IL-4 and IL-13 caused a rapid and potent induction of 3beta-HSD type 1 gene expression. Such an induction was also observed in normal human mammary and prostate epithelial cells in primary culture as well as in human HaCaT immortalized keratinocytes, ME-180 cervix cancer cells, and HT-29 colon cancer cells. The DNA-binding activity of Stat6, a member of the Signal Transducers and Activators of Transcription gene family, was activated after a 30 min exposure to IL-4 in all the cell types where IL-4 induced 3beta-HSD expression, but not in those that failed to respond to IL-4. Our data therefore suggest that IL-4 and IL-13 may play a role in the biosynthesis of active sex steroids from the inactive adrenal steroid DHEA, not only in breast cells but also in various cell types derived from peripheral target tissues.

Role of 17 beta-hydroxysteroid dehydrogenases in sex steroid formation in peripheral intracrine tissues

In postmenopausal women, almost 100% of active sex steroids are synthesized in peripheral target tissues from inactive steroid precursors and, in adult men, approximately 50% of androgens are made locally in target tissues. This new field of endocrinology has been called intracrinology. The last and key step in the formation of all estrogens and androgens is catalyzed by a series of substrate-specific, cell-specific and unidirectional 17 beta-hydroxysteroid dehydrogenases (17 beta-HSDs). To date, seven human 17 beta-HSDs have been cloned, sequenced and characterized. The 17 beta-HSDs provide each cell with the means of precisely controlling the intracellular concentration of each sex steroid according to local needs.

Anastrozole is superior to tamoxifen as first-line therapy for advanced breast cancer in postmenopausal women: results of a North American multicenter randomized trial. Arimidex Study Group

PURPOSE

The efficacy and tolerability of anastrozole (Arimidex; AstraZeneca, Wilmington, DE, and Macclesfield, United Kingdom) and tamoxifen were compared as first-line therapy for advanced breast cancer in 353 postmenopausal women.

PATIENTS AND METHODS

The randomized, double-blind, multicenter study was designed to evaluate anastrozole 1 mg once daily relative to tamoxifen 20 mg once daily in patients with hormone receptor-positive tumors or tumors of unknown receptor status who were eligible for endocrine therapy. Primary end points were objective response (OR), defined as complete (CR) or partial (PR) response, time to progression (TTP), and tolerability.

RESULTS

Anastrozole was as effective as tamoxifen in terms of OR (21% v 17% of patients, respectively), with clinical benefit (CR + PR + stabilization > or = 24 weeks) observed in 59% of patients on anastrozole and 46% on tamoxifen (two-sided P =.0098, retrospective analysis). Anastrozole had a significant advantage over tamoxifen in terms of TTP (median TTP of 11.1 and 5.6 months for anastrozole and tamoxifen, respectively; two-sided P =.005). The tamoxifen:anastrozole hazards ratio was 1.44 (lower one-sided 95% confidence limit, 1.16). Both treatments were well tolerated. However, thromboembolic events and vaginal bleeding were reported in fewer patients who received anastrozole compared with those who received tamoxifen (4.1% v 8.2% [thromboembolic events] and 1.2% v 3.8% [vaginal bleeding], respectively).

CONCLUSION

Anastrozole satisfied the predefined criteria for equivalence to tamoxifen. Furthermore, we observed both a significant increase in TTP and a lower incidence of thromboembolic events and vaginal bleeding with anastrozole. These findings indicate that anastrozole should be considered as first-line therapy for postmenopausal women with advanced breast cancer.

Anastrozole versus tamoxifen as first-line therapy for advanced breast cancer in 668 postmenopausal women: results of the Tamoxifen or Arimidex Randomized Group Efficacy and Tolerability study

PURPOSE

To compare the efficacy and tolerability of anastrozole (Arimidex; AstraZeneca, Wilmington, DE, and Macclesfield, United Kingdom) with that of tamoxifen as first-line therapy for advanced breast cancer (ABC) in postmenopausal women.

PATIENTS AND METHODS

This randomized, double-blind, multicenter study evaluated the efficacy of anastrozole 1 mg once daily relative to tamoxifen 20 mg once daily in patients with tumors that were hormone receptor-positive or of unknown receptor status who were eligible for endocrine therapy. The primary end points were time to progression (TTP), objective response (OR), and tolerability.

RESULTS

A total of 668 patients (340 in the anastrozole arm and 328 in the tamoxifen arm) were randomized to treatment and followed-up for a median of 19 months. Median TTP was similar for both treatments (8.2 months in patients who received anastrozole and 8.3 months in patients who received tamoxifen). The tamoxifen:anastrozole hazards ratio was 0.99 (lower one-sided 95% confidence limit, 0.86), demonstrating that anastrozole was at least equivalent to tamoxifen. Anastrozole was also as effective as tamoxifen in terms of OR (32.9% of anastrozole and 32.6% of tamoxifen patients achieved a complete response [CR] or partial response [PR]). Clinical benefit (CR + PR + stabilization of > or = 24 weeks) rates were 56.2% and 55.5% for patients receiving anastrozole and tamoxifen, respectively. Both treatments were well tolerated. However, incidences of thromboembolic events and vaginal bleeding were reported in fewer patients treated with anastrozole than with tamoxifen (4.8% v 7.3% [thromboembolic events] and 1.2% v 2.4% [vaginal bleeding], respectively).

CONCLUSION

Anastrozole satisfied the predefined criteria for equivalence to tamoxifen. Together with the lower observed incidence of thromboembolic events and vaginal bleeding, these findings indicate that anastrozole should be considered as first-line therapy for postmenopausal women with ABC.

Survival in patients with metastatic breast cancer: analysis of randomized studies comparing oral aromatase inhibitors versus megestrol

In patients with metastatic breast cancer, second-line therapy with aromatase inhibitors can improve survival in comparison with megestrol. We conducted a meta-analysis to assess the effectiveness of aromatase inhibitors versus megestrol. After a Medline search, three trials (evaluating letrozole, anastrozole or exemestane versus megestrol) were included in the survival meta-analysis. Our methodology retrieved patient-level information on survival. In comparison with megestrol, aromatase inhibitors prolonged survival at levels of statistical significance (relative death risk for oral aromatase inhibitors=0.79, 95% confidence interval 0.69-0.91; p=0.0011). A lifetime analysis of the pooled survival curves of aromatase inhibitors versus megestrol found a mean survival gain of 4.1 months per patient. Aromatase inhibitors confer a significant survival benefit to patients with metastatic breast cancer as compared with megestrol. A preliminary calculation of the cost per life year gained shows that the pharmacoeconomic profile of these drugs is favorable.

Exemestane in breast cancer: current status and future directions

Exemestane is a novel, potent, and specific third-generation aromatase inactivator developed for breast can-cer therapy. The drug is effective in patients with metastatic disease failing tamoxifen alone or tamoxifen followed by megestrol acetate or a nonsteroidal aromatase inhibitor. In a phase III study, exemestane was superior to megestrol acetate in overall survival, time to tumor progression, and time to treatment failure in women with metastatic disease who experienced failure of tamoxifen. Preliminary evidence suggests activity to exemestane exceeds that obtained with tamoxifen as first-line treatment. Two studies are comparing sequential treatment with tamoxifen followed by exemestane to tamoxifen monotherapy in the adjuvant setting. A third study is comparing the toxicity profile of exemestane with that of placebo in patients with early breast cancer who are at low risk of relapse. The findings from these studies will determine the role of exemestane in early breast cancer and lay the foundation for assessing its potential role in breast cancer prevention.

An overview of the use of non-steroidal aromatase inhibitors in the treatment of breast cancer

A number of potent and selective non-steroidal aromatase inhibitors are now available for the treatment of advanced breast cancer in postmenopausal women. In particular, anastrozole represents a significant advantage over earlier agents, such as aminoglutethimide and formestane, in terms of both efficacy and tolerability. These agents are now established as the second-line therapy of choice in postmenopausal women with advanced disease progressing on tamoxifen and, furthermore, data are now available on the efficacy and tolerability of anastrozole as first-line treatment of advanced breast cancer compared with tamoxifen. The full potential of the new-generation aromatase inhibitors in the treatment of breast cancer is currently being investigated in a large programme of clinical trials, including evaluation as neoadjuvant treatment in postmenopausal women with newly-diagnosed locally-advanced or large operable breast cancers, as first-line treatment of advanced breast cancer in postmenopausal women. Aromatase inhibitors have been available for over 20 years; the ability of these compounds to reduce circulating oestradiol levels has been shown to produce clinical benefit in postmenopausal women with advanced breast cancer. Early aromatase inhibitors, however, such as aminoglutethimide and formestane, were not specific for the aromatase enzyme and resulted in significant side-effects.

Advanced breast cancer: recent developments in hormonal therapy

OBJECTIVES

To review recent developments in hormonal therapy for metastatic breast cancer.

DATA SOURCES

Published books and articles.

CONCLUSIONS

Newer hormonal agents are offering women alternatives for sequential therapy of metastatic disease that provide benefit with less risk.

IMPLICATIONS FOR NURSING PRACTICE

A thorough understanding of the relationship between hormonal influences and breast cancer will assist nurses to better appreciate the variety of agents now available and their specific indications, outcomes, and effects. Common side effects include weight gain, hot flashes, nausea, and skin and vaginal changes. Nursing efforts focus on the areas of body image disturbance, side effect management, and fostering healthy relationships.