Clinical and endocrine data for goserelin plus anastrozole as second-line endocrine therapy for premenopausal advanced breast cancer

Goserelin plus letrozole as first- or second-line hormonal treatment in premenopausal patients with advanced breast cancer

A promising new option as the treatment of choice for premenopausal patients with metastatic breast cancer (MBC) could be the combination of a luteinising hormone-releasing hormone analog and an aromatase inhibitor. Very little data about the use of goserelin with anastrozole in advanced breast cancer are available, and no cohort studies on the efficacy of goserelin with letrozole in advanced premenopausal breast cancer patients have been reported. We present the single-centre, retrospective, experience of goserelin plus letrozole in a total of 52 premenopausal women with MBC. All patients received goserelin 3.6 mg by subcutaneous injection every 4 weeks along with letrozole 2.5 mg daily as first-line (n=36) and second-line (n=16) hormonal treatment. The median duration of goserelin with letrozole treatment was 11 (range, 2-61) months, and the median duration of overall follow-up was 31 (range, 3-66) months. The objective response rate (ORR) was 21.1%, with two complete response (CR) (3.8%) and nine partial response (PR) (17.3%). Stable disease (SD) lasting more than 6 months was achieved by 26 patients (50.0%). Thus, goserelin with letrozole conferred clinical benefit (CB) in 37 women (71.1%). The progression-free survival (PFS) was 10 months. CR was exclusively observed in hormone receptor-double-positive patients. Drug therapy was well tolerated; no grade 3/4 toxicities were reported. Goserelin plus letrozole appears to be an efficacious and well-tolerated regimen in women with advanced breast cancer. Further prospectively randomized studies involving more patients and longer follow-up are indicated.

Suppression of ovarian function in combination with an aromatase inhibitor as treatment for advanced breast cancer in pre-menopausal women

Trials have shown superiority of aromatase inhibitors (AIs) over tamoxifen for post-menopausal oestrogen receptor-positive advanced breast cancer (ER+ABC). We previously reported the use of goserelin plus anastrozole (G+A) as second-line endocrine therapy for pre-menopausal ER+ABC. We report clinical and endocrine data from G+A as first-line systemic therapy. Thirty-six patients (median age=44 years) with metastatic (N=28) and locally advanced disease were administered G+A for ≥6 months (unless progressed prior). Some (N=13) received further therapy with goserelin plus another AI (steroidal), exemestane (G+E). Serial serum hormone assays (oestradiol, dehydroepiandrosterone sulphate, testosterone, follicle stimulating hormone and luteinising hormone) were performed. Twenty-four patients (67%) derived clinical benefit (CB) (5% complete response, 31% partial response, 31% stable disease for ≥6 months) with median time to progression and duration of CB of 12 (2-47) and 24+(7-78+) months respectively. Ten patients were still receiving first-line G+A at analysis. Amongst 13 patients who went onto receive G+E, 38% achieved CB with a mean duration of 13+(7-32) months. Therapy was well tolerated with no withdrawals. The combination of G+A resulted in 98% reduction (from pre-treatment to 6-month) in median levels of oestradiol (from 574.5 pmol/L; inter-quartile range (IQR)=209-1426; (N=6) to 13.45 pmol/L; IOQ=5.5-31.5 (N=4) whilst the levels of other hormones had minimal fluctuations during therapy. The combinations of ovarian function suppression (using G) and AIs produce sustained CB and minimal side effects in pre-menopausal ER+ABC with significant reduction in oestradiol levels. Within the limitations of being a non-randomised study, they should be considered in appropriate patients with hormone-sensitive ABC.

Phase II Trial of Anastrozole Plus Goserelin in the Treatment of Hormone Receptor–Positive, Metastatic Carcinoma of the Breast in Premenopausal Women

Purpose

To explore the antitumor activity of the aromatase inhibitor, anastrozole, in the treatment of premenopausal women with hormone receptor–positive, metastatic breast cancer who have been rendered functionally postmenopausal with the use of the luteinizing hormone-releasing hormone agonist, goserelin.

Patients and Methods

Premenopausal women with estrogen and/or progesterone receptor–positive, metastatic or recurrent breast cancer were enrolled in this prospective, single-arm, multicenter phase II trial. Patients were treated with goserelin 3.6 mg subcutaneous monthly and began anastrozole 1-mg daily 21 days after the first injection of goserelin. Patients continued on treatment until disease progression or unacceptable toxicity.

Results

Thirty-five patients were enrolled of which 32 were evaluable for response and toxicity. Estradiol suppression was assessed, with mean estradiol levels of 18.7 pg/mL at 3 months and 14.8 pg/mL at 6 months. One participant (3.1%) experienced a complete response, 11 (34.4%) experienced partial response, and 11 (34.4%) experienced stable disease for 6 months or longer for a clinical benefit rate of 71.9%. Median time to progression was 8.3 months (range, 2.1 to 63+) and median survival was not been reached (range, 11.1 to 63+). The most common adverse events were fatigue (50%), arthralgias (53%), and hot flashes (59%). There were no grade 4 to 5 toxicities.

Conclusion

The combination of goserelin plus anastrozole has substantial antitumor activity in the treatment of premenopausal women with hormone receptor–positive metastatic breast cancer.

Safety and tolerability of zoledronic acid and other bisphosphonates in osteoporosis management

Bisphosphonates (BPs) are widely used in the treatment of postmenopausal osteoporosis and other metabolic bone diseases. They bind strongly to bone matrix and reduce bone loss through inhibition of osteoclast activity. They are classified as nitrogen- and non-nitrogen-containing bisphosphonates (NBPs and NNBPs, respectively). The former inhibit farnesyl diphosphate synthase while the latter induce the production of toxic analogs of adenosine triphosphate. These mechanisms of action are associated with different antifracture efficacy, and NBPs show the most powerful action. Moreover, recent evidence indicates that NBPs can also stimulate osteoblast activity and differentiation. Several randomized control trials have demonstrated that NBPs significantly improve bone mineral density, suppress bone turnover, and reduce the incidence of both vertebral and nonvertebral fragility fractures. Although they are generally considered safe, some side effects are reported (esophagitis, acute phase reaction, hypocalcemia, uveitis), and compliance with therapy is often inadequate. In particular, gastrointestinal discomfort is frequent with the older daily oral administrations and is responsible for a high proportion of discontinuation. The most recent weekly and monthly formulations, and in particular the yearly infusion of zoledronate, significantly improve persistence with treatment, and optimize clinical, densitometric, and antifracture outcomes.

Optimal adjuvant endocrine therapy for early breast cancer

Adjuvant endocrine therapy substantially reduces tumor recurrence and mortality in pre- and post-menopausal women with hormone receptor-positive early breast cancer but is ineffective in women with hormone receptor-negative tumors. Tamoxifen has been the standard adjuvant endocrine therapy for both pre- and post-menopausal women with hormone receptor-positive early breast cancer and remains the standard of care for premenopausal women. In addition to tamoxifen, ovarian ablation by surgery or radiotherapy remains an option for selected premenopausal women and trials are evaluating the role of ovarian function suppression using luteinizing hormone-releasing hormone agonists. For postmenopausal women, aromatase inhibitors are more effective than tamoxifen therapy and aromatase inhibitors and tamoxifen are regarded as standards of care. Prolonging adjuvant endocrine therapy in postmenopausal women by the sequencing of aromatase inhibitors and tamoxifen can improve outcomes further. Adjuvant endocrine therapy will probably be used for longer durations in selected postmenopausal women.

Pharmacoeconomic considerations in the treatment of breast cancer

Breast cancer is the most common malignancy in women worldwide and causes great economic burden. The aim of this paper is to present the available clinical and pharmacoeconomic evidence associated with different therapies for breast cancer. As significant progress was made in recent years and there are many alternative treatments, which are indicated according to the stage and the type of the disease, the age and health status of patient, and vary from surgery to hormonal treatment and chemotherapy. A broad literature review was undertaken and the paper presents the evidence available regarding the effectiveness and cost-effectiveness of the alternative options. Despite the high cost of most therapies and perceptions that treatments in this area may not be cost-effective, due to a combination of high costs and short survival, based on the literature review treatment options for breast cancer are in general deemed to be cost-effective. Time horizon, stage of the disease, patient age, therapy onset, benefit duration and time to recurrence may influence the results. Pharmacoeconomic analyses of alternative therapy options will improve decision-making and will help to optimize the use of scarce health care resources allocated to the care of breast cancer patients.

Phase II Parallel Group Study Showing Comparable Efficacy Between Premenopausal Metastatic Breast Cancer Patients Treated With Letrozole Plus Goserelin and Postmenopausal Patients Treated With Letrozole Alone As First-Line Hormone Therapy

Purpose

Goserelin and letrozole in premenopausal patients can result in clinical outcomes comparable to those obtained by letrozole alone in postmenopausal patients with metastatic breast cancer (MBC).

Patients and Methods

A total of 73 patients with hormone-responsive MBC were included. Of those, 35 premenopausal patients received goserelin (3.6 mg subcutaneously every 28 days) plus letrozole (2.5 mg orally daily), and 38 postmenopausal patients received letrozole alone as their first-line endocrine therapy in a metastatic setting.

Results

Baseline characteristics were similar in the two groups, except for a younger age (median, 41 v 53.5 years; P < .001) and a shorter disease-free interval (median, 1.8 v 3.3 years; P = .03) in the premenopausal group. Clinical benefit rates were comparable between the two groups (77% v 74%; P = .77). With the median follow-up of 27.4 months, there was no statistical difference in the median time to progression between the two groups (9.5 months [95% CI, 6.4 to 12.1 months] v 8.9 months [95% CI, 6.4 to 13.3 months]). In patients who did not receive bisphosphonate, letrozole ± goserelin caused a greater loss of bone mineral density at 6 months compared with that of patients receiving bisphosphonate treatment (premenopausal group, −16.7% v 53.9%; P = .002 and postmenopausal group, −13.3% v 17.4%; P = .04 at the lumbar spine).

Conclusion

Clinical efficacies in premenopausal MBC patients with combined letrozole and goserelin therapy were comparable to those in postmenopausal patients treated with letrozole alone. Although letrozole ± goserelin resulted in a modest increase in bone resorption, concurrent treatment with bisphosphonate could prevent bone loss at 6 months.

Adjuvant endocrine therapy of premenopausal women with early breast cancer: an overview

Tamoxifen is currently the standard of care for premenopausal women with hormone receptor-positive early breast cancers. However, endocrine strategies in premenopausal women include not only estrogen receptor blockade with tamoxifen but also temporary suppression of ovarian estrogen synthesis by luteinizing hormone-releasing hormone (LHRH) agonists, or permanent interruption of ovarian estrogen synthesis with oophorectomy or radiotherapy. Luteinizing hormone-releasing hormone agonists have proven to be as effective as surgical oophorectomy in adjuvant treatment of premenopausal breast cancer. The addition of LHRH agonists compared to no therapy reduces the annual odds of recurrence and death in premenopausal women aged less than 50 years with estrogen receptor-positive tumors. Luteinizing hormone-releasing hormone agonists alone or in combination with tamoxifen have shown disease-free survival rates similar to chemotherapy with CMF (cyclophosphamide/methotrexate/5-fluorouracil) and other second-generation chemotherapies. The role of aromatase inhibitors in combination with ovarian suppression is still not established, especially as a large phase III randomized study (Austrian Breast and Colorectal Cancer Study Group Trial 12) did not show superior efficacy compared with ovarian suppression plus tamoxifen in premenopausal early stage disease. Patients currently continue to receive ovarian suppression and tamoxifen. CYP2D6 status may become an important discriminator for the type of endocrine therapy for the premenopausal patient in the future.

Adjuvant endocrine therapy for premenopausal women with breast cancer

AIMS

Endocrine therapy is a pivotal treatment for women with hormone-receptor positive breast cancer. In premenopausal women, endocrine therapy primarily consists of tamoxifen and ovarian suppressive strategies. Younger women experience improvements in the risks of relapse or death from breast cancer with the use of chemotherapy as well, with part of this benefit explained by resultant premature amenorrhea. Unfortunately despite a centuries worth of clinical trials, the most efficacious combination of hormonal therapies and chemotherapy has yet to be determined. This paper serves as a comprehensive review of the substantial data in the adjuvant treatment of premenopausal, hormone receptor-positive women with breast cancer.

METHODS AND RESULTS

PubMed and American Society of Clinical Oncology (ASCO) Proceedings searches from 1896 to present were performed. All of the trials examining the role of ovarian suppression and tamoxifen with and without chemotherapy in premenopausal women were included. The current data suggests that endocrine therapy can be an important alternative to chemotherapy in select patient populations, and improvements in outcome are also seen with the combination of hormonal and chemotherapy strategies in other populations. A majority of the trials examined did not use what is considered to be current standards of care regarding chemotherapy regimens and durations of adjuvant hormonal therapy. Many unanswered questions remain particularly regarding the combined use of ovarian suppression and tamoxifen in women who are also receiving chemotherapy.

CONCLUSION

There is a persistent need to define optimal endocrine therapy in premenopasusal women with hormone-receptor positive breast cancer. Contemporaneous trials, such as the SOFT trial will provide direction, and additional biomarker and pharmacogenomic data will further supplement individualized patient decision making.

Recurrent breast cancer: treatment strategies for maintaining and prolonging good quality of life

BACKGROUND

Recurrent breast cancer remains a challenge for interdisciplinary treatment even though new therapeutic options are available.

METHODS

The PubMed database was selectively searched for articles that appeared from 1999 to 2009 and contained the key words "breast cancer," "recurrence," "metastatic," "advanced," and "treatment". Further sources consulted for this review included the German S3 guideline, the treatment recommendations of the German AGO-Mamma group, the NCCN guidelines, and the Cochrane database.

RESULTS

Locoregional recurrences are treated with curative intent. Metastatic breast cancer must be treated on an individualized basis: The treatment should be continued as long as its benefits for the individual patient outweigh its adverse side effects. Endocrine treatment is indicated for all patients whose tumors are hormone-receptor positive or of unknown receptor status and who have enough time for a response to be seen. Chemotherapy should be given if the tumor is hormone-receptor negative, if a rapid response is urgently needed, or if endocrine treatment has failed to produce a response. Combination chemotherapy improves response rates and prolongs progression-free survival, yet it does not prolong overall survival in comparison to monochemotherapy. In HER2-positive patients, first-line treatment with trastuzumab and monochemotherapy prolongs overall survival. Other treatment options include angiogenesis inhibitors, various tyrosine kinases inhibitors, radiotherapy, bisphosphonates, surgical or other ablative treatment of metastases, or a combination of these approaches, applied either simultaneously or consecutively.

CONCLUSIONS

While locoregional recurrences of breast cancer should be treated with curative intent, breast cancer with distant metastases is currently not curable. It is treated with the intention of restoring and maintaining good quality of life and relieving symptoms due to the metastases, rather than prolonging survival.

Breast cancer: beyond the cutting edge

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

LHRH agonists for adjuvant therapy of early breast cancer in premenopausal women

BACKGROUND

Approximately 60% of breast cancers amongst premenopausal women express the nuclear oestrogen receptor (ER+ breast cancer). Adjuvant endocrine therapy is an integral component of care for ER+ breast cancer, exerting its effect by reducing the availability of oestrogen to micrometastatic tumour cells. Endocrine strategies in premenopausal women include oestrogen receptor blockade with tamoxifen, temporary suppression of ovarian oestrogen synthesis by luteinising hormone releasing hormone (LHRH) agonists, or permanent interruption of ovarian oestrogen synthesis with oophorectomy or radiotherapy. Aromatase inhibitors are also available with concurrent suppression of ovarian oestrogen synthesis, either through LHRH agonists, surgery, or radiotherapy. Chemotherapy can also have an endocrine action in premenopausal women by interrupting ovarian oestrogen production, either temporarily or permanently. International consensus statements recommend single agent tamoxifen as the current standard adjuvant endocrine therapy for premenopausal women (often preceded by chemotherapy), and the role of LHRH agonists remains under active investigation.

OBJECTIVES

To assess LHRH agonists as adjuvant therapy for women with early breast cancer.

SEARCH STRATEGY

The Cochrane Breast Cancer Group Specialised Register was searched on 19 February 2009. This register incorporates references from CENTRAL (The Cochrane Library) (to 2002), MEDLINE (1966 to July 2008), EMBASE (until 2002); and handsearches of abstracts from the San Antonio Breast Cancer Symposium, American Society of Clinical Oncology Annual Meeting, and the Clinical Oncological Society of Australia Annual Meeting. MEDLINE references (from August 2008 to 19th February 2009) were checked by the authors. The reference lists of related reviews were checked. A final check of the list of trials maintained by the Early Breast Cancer Trialists' Collaborative Group was made in January 2008.

SELECTION CRITERIA

All randomised trials assessing LHRH agonists as adjuvant treatment in premenopausal women with early stage breast cancer were included. Specifically, we included trials that compared:(A) LHRH agonists (experimental arm) versus another treatment;(B) LHRH agonists + anti-oestrogen (experimental arm) versus another treatment;(C) LHRH agonists + chemotherapy (experimental arm) versus another treatment;(D) LHRH agonists + anti-oestrogen + chemotherapy (experimental arm) versus another treatment.

DATA COLLECTION AND ANALYSIS

Data were collected from trial reports. We reported estimates for the differences between treatments on recurrence free survival, overall survival, toxicity and quality of life using data available in the reports of each trial. Meta-analyses were not performed because of variability in the reporting of the trials.

MAIN RESULTS

We identified 14 randomised trials that involved over 13,000 premenopausal women with operable breast cancer, most of whom were ER+. The numbers of trials making the different comparisons were:(A) i. LHRH versus tamoxifen (three trials),ii. LHRH versus chemotherapy (four trials);(B) i. LHRH + tamoxifen versus tamoxifen (two trials),ii. LHRH + tamoxifen versus LHRH (three trials),iii. LHRH + tamoxifen versus chemotherapy (two trials),iv. LHRH + aromatase inhibitor versus LHRH + tamoxifen (one trial);(C) i. LHRH + chemotherapy versus LHRH (one trial),ii. LHRH + chemotherapy versus chemotherapy (five trials);(D) LHRH + tamoxifen + chemotherapy versus chemotherapy (three trials).The LHRH agonist in most of these trials was goserelin.For most of the treatment comparisons there are too few trials, too few randomised patients, or too little follow up to draw reliable estimates of the relative effects of different treatments.(A) LHRH monotherapy: results suggest that adjuvant LHRH agonist monotherapy is similar to older chemotherapy protocols (eg. CMF) in terms of recurrence-free and overall survival in ER+ patients. There are insufficient data to compare LHRH agonist monotherapy to tamoxifen alone, but available results suggest that these treatments are comparable in terms of recurrence-free survival.(B) LHRH + anti-oestrogen therapy: there are insufficient data to compare the combination of an LHRH agonist plus tamoxifen to tamoxifen alone. Results suggest that the LHRH agonist plus tamoxifen combination may be superior to an LHRH agonist alone or to chemotherapy alone, but the chemotherapy protocols tested are outdated. The data comparing LHRH agonists plus aromatase inhibitors to LHRH agonists plus tamoxifen are currently inconclusive.(C) LHRH + chemotherapy: there are insufficient data to compare the LHRH + chemotherapy combination to an LHRH agonist alone, although results from a single study suggest comparable efficacy in ER+ patients. There is a trend towards improved recurrence-free and overall survival in patients who received an LHRH agonist plus chemotherapy combination in comparison to chemotherapy alone.(D) LHRH agonist + chemotherapy + tamoxifen: there is a trend towards improved recurrence-free and overall survival in patients who received an LHRH agonist plus tamoxifen plus chemotherapy in comparison to chemotherapy alone.There are insufficient data to assess the effect of the addition of LHRH agonists to the current standard treatment of chemotherapy plus tamoxifen.Endocrine therapy with LHRH agonists appears to have fewer side-effects than the forms of chemotherapy assessed. The optimal duration of LHRH therapy in the adjuvant setting is unclear.

AUTHORS' CONCLUSIONS

Overall, the data from currently published clinical trials of LHRH agonists in the adjuvant setting for premenopausal women with endocrine-sensitive breast cancer are supportive of clinical benefit. Nonetheless, definitive comparisons against current clinical standards of care that include third generation chemotherapy regimens and tamoxifen are required before their place in the adjuvant setting can be properly defined. The authors conclude that the current data strongly support the continuation of current trials that definitively compare a variety of combinations of LHRH agonists and anti-oestrogenic strategies to the current standard of five years of tamoxifen.

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

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

Endocrine therapy plus zoledronic acid in premenopausal breast cancer

BACKGROUND

Ovarian suppression plus tamoxifen is a standard adjuvant treatment in premenopausal women with endocrine-responsive breast cancer. Aromatase inhibitors are superior to tamoxifen in postmenopausal patients, and preclinical data suggest that zoledronic acid has antitumor properties.

METHODS

We examined the effect of adding zoledronic acid to a combination of either goserelin and tamoxifen or goserelin and anastrozole in premenopausal women with endocrine-responsive early breast cancer. We randomly assigned 1803 patients to receive goserelin (3.6 mg given subcutaneously every 28 days) plus tamoxifen (20 mg per day given orally) or anastrozole (1 mg per day given orally) with or without zoledronic acid (4 mg given intravenously every 6 months) for 3 years. The primary end point was disease-free survival; recurrence-free survival and overall survival were secondary end points.

RESULTS

After a median follow-up of 47.8 months, 137 events had occurred, with disease-free survival rates of 92.8% in the tamoxifen group, 92.0% in the anastrozole group, 90.8% in the group that received endocrine therapy alone, and 94.0% in the group that received endocrine therapy with zoledronic acid. There was no significant difference in disease-free survival between the anastrozole and tamoxifen groups (hazard ratio for disease progression in the anastrozole group, 1.10; 95% confidence interval [CI], 0.78 to 1.53; P=0.59). The addition of zoledronic acid to endocrine therapy, as compared with endocrine therapy without zoledronic acid, resulted in an absolute reduction of 3.2 percentage points and a relative reduction of 36% in the risk of disease progression (hazard ratio, 0.64; 95% CI, 0.46 to 0.91; P=0.01); the addition of zoledronic acid did not significantly reduce the risk of death (hazard ratio, 0.60; 95% CI, 0.32 to 1.11; P=0.11). Adverse events were consistent with known drug-safety profiles.

CONCLUSIONS

The addition of zoledronic acid to adjuvant endocrine therapy improves disease-free survival in premenopausal patients with estrogen-responsive early breast cancer. (ClinicalTrials.gov number, NCT00295646.)

Endocrine therapy of metastatic breast cancer

Breast cancer growth and dissemination is regulated by estrogen and different growth factor receptor signalling pathways. The increasing knowledge of the biology of breast cancer regarding the interaction of these signalling pathways provides a tool to understand endocrine therapies response and resistance mechanisms. In patients with slowly progressive disease, no visceral involvement, and minimal symptoms, endocrine therapy could be the strategy of choice, even if the tumor has low estrogen receptor expression. Ovarian suppression and tamoxifen are recommended for premenopausal patients whether aromatase inhibitors are the option for postmenopausal ones. Chemotherapy still remains as the right alternative for hormone unresponsive or resistant patients. This is a review focused on the different strategies and combinations of endocrine therapies for metastatic breast cancer patients considering the potential strategies clinically tested to overcome resistance and the different treatments of choice available for each scenario of disseminated disease.

The influence of endocrine treatments for breast cancer on health-related quality of life

Many hormonal modalities are available for breast cancer treatment, such as selective oestrogen receptor modulators (SERMs), aromatase inhibitors, progestins and luteinising hormone-releasing hormone (LHRH) agonists. The long-term impact of these endocrine manipulations is an issue, because the duration of adjuvant treatment is still increasing, as is the number of breast cancer survivors. Premature menopause is induced at a young age, and may often be permanent after chemotherapy. The purpose of this review is to provide a literature-based overview of the side effects of endocrine treatment in pre- and postmenopausal breast cancer patients and the influence on HRQoL, especially on sexual functioning. The collection of health-related quality of life (HRQoL) data can result in better treatment recommendations during endocrine therapy.

METHODS

This review was limited to prospective randomised studies in English literature from between 1977 and 2007 and provides an overview of the effects on HRQoL and sexuality of various hormonal treatment in pre- and postmenopausal breast cancer patients, both in the adjuvant and palliative setting. Relevant clinical studies were identified by using the Medline database.

RESULTS

HRQoL mostly is severely influenced by chemotherapy and part of these symptoms may be lasting, especially when associated with the induction of premature menopause. Similar symptoms may be encountered during ovarian suppression therapy by LHRH analogs, but they will usually prove to be reversible. The varying side effect profiles of tamoxifen and aromatase inhibitors did not lead to significant difference in overall HRQoL. HRQoL during progestins and the SERM fulvestrant has been compared to this during aromatase inhibitors, and a large number of studies on HRQoL during endocrine therapy will be discussed.

Adjuvant Endocrine Therapy in Premenopausal Patients

Endocrine adjuvant therapy is the best-described molecular targeted treatment and should therefore be used for all patients with endocrine-responsive breast cancer. Ta-moxifen for 5 years is standard of care and has proven efficacy in premenopausal patients. The combination of tamoxifen with ovarian function suppression and/or chemotherapy has been extensively tested, and some controversial approaches are used in clinical practice. Cessation or suppression of ovarian function appears to be beneficial for premenopausal patients. Particularly for premenopausal women with highly endocrine-responsive disease and/or low risk for relapse, the additional benefit of cytotoxic chemotherapy may be minor or nonexistent. While the use aromatase inhibitors is investigated in clinical trials, their application outside an academic trial setting cannot be recommended based on first available results. In contrast, the use of adjuvant bispho-sphonates may offer another strategy of further improving clinical outcomes in this important patient subgroup.

Endocrine effects of adjuvant letrozole + triptorelin compared with tamoxifen + triptorelin in premenopausal patients with early breast cancer

PURPOSE

To compare the endocrine effects of 6 months of adjuvant treatment with letrozole + triptorelin or tamoxifen + triptorelin in premenopausal patients with early breast cancer within an ongoing phase 3 trial (Hormonal Adjuvant Treatment Bone Effects study).

PATIENTS AND METHODS

Prospectively collected hormonal data were available for 81 premenopausal women, of whom 30 were assigned to receive tamoxifen + triptorelin and 51 were assigned letrozole + triptorelin +/- zoledronate. Serum 17-beta-estradiol (E2), follicle-stimulating hormone (FSH), luteinizing hormone (LH), Delta4-androstenedione, testosterone, dehydroepiandrosterone-sulfate, progesterone, adrenocorticotropic hormone (ACTH), and cortisol were measured at baseline and after 6 months of treatment. For each hormone, 6-month values were compared between treatment groups by the Wilcoxon-Mann-Whitney exact test.

RESULTS

Median age was 44 years for both groups of patients. Letrozole + triptorelin (+/- zoledronate) induced a stronger suppression of median E2 serum levels (P = .0008), LH levels (P = .0005), and cortisol serum levels (P < .0001) compared with tamoxifen + triptorelin. Median FSH serum levels were suppressed in both groups, but such suppression was lower among patients receiving letrozole, who showed significantly higher median FSH serum levels (P < .0001). No significant differences were observed for testosterone, progesterone, ACTH, androstenedione, and dehydroepiandrosterone between the two groups of patients.

CONCLUSION

Letrozole in combination with triptorelin induces a more intense estrogen suppression than tamoxifen + triptorelin in premenopausal patients with early breast cancer.

The what, why and how of aromatase inhibitors: hormonal agents for treatment and prevention of breast cancer

The third-generation aromatase inhibitors (AIs) anastrozole, exemestane and letrozole have largely replaced tamoxifen as the preferred treatment for hormone receptor - positive breast cancer in postmenopausal women. Approximately 185,000 new cases of invasive breast cancer are diagnosed yearly, and at least half of these women are both postmenopausal and eligible for adjuvant therapy with AIs. In addition, AIs are currently being tested as primary prevention therapy in large randomised trials involving tens of thousands of women at increased risk for breast cancer. Given the volume of use, internists will increasingly see postmenopausal women who are taking or considering treatment with AIs. Physicians need to be able to: (i) briefly discuss the pros and cons of using a selective estrogen receptor modulator such as tamoxifen or raloxifene vs. an AI for risk reduction and (ii) recognise and manage AI-associated adverse events. The primary purpose of this review is to help internists with these two tasks.

Controversies of adjuvant endocrine treatment for breast cancer and recommendations of the 2007 St Gallen conference

Endocrine treatment for breast cancer was introduced more than a century ago. The discovery of hormone receptors has allowed targeting of endocrine treatment to patients whose primary tumours express these receptors. In the adjuvant setting, different approaches are used in premenopausal or postmenopausal women. In premenopausal patients, suppression of ovarian function and the use of tamoxifen are the most important therapeutic options, even though questions on timing, duration, and combination of these compounds remain unanswered. The use of aromatase inhibitors in combination with ovarian-function suppression is currently under investigation in the premenopausal setting. In postmenopausal patients, aromatase inhibitors given after 2-3 years or 5 years of tamoxifen have shown a significant benefit over tamoxifen alone. However, questions on this treatment also remain unanswered. For example, whether all patients should receive an aromatase inhibitor or whether some subgroups of patients might be optimally treated by tamoxifen alone is yet to be established. In this paper we review the published work on adjuvant endocrine treatment in breast cancer and provide recommendations from the 2007 St Gallen International Conference on Primary Therapy of Early Breast Cancer.

Current clinical trials of endocrine therapy for breast cancer

Breast cancer is a hormone-dependent cancer like prostate cancer and endometrial cancer. Estrogen plays important roles in the development and progression of breast cancer. Endocrine therapy is the treatment of choice for estrogen receptor- and/or progesterone receptor-positive breast cancer. Endocrine therapy has been used for several purposes, including chemoprevention, preoperative treatment, postoperative adjuvant treatment and treatment for recurrent diseases. A large number of clinical trials have provided evidence showing the clinical benefits of various endocrine therapies for the treatment of breast cancer. The current status and recent advances in endocrine therapy for breast cancer are reviewed based on the results of current clinical trials. Future perspectives of endocrine therapy are also discussed.

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.

Aromatase inhibitors for breast cancer

Endocrine therapy is a mainstay for the many women who develop in situ or invasive steroid receptor-positive breast cancer. The use of tamoxifen has reduced mortality in such women. Recently estrogen deprivation strategies have come under scrutiny. Here the use of aromatase inhibitors for treatment of postmenopausal endocrine-responsive breast cancer in the metastatic, adjuvant, and preoperative settings is reviewed.

Antitumour and biological effects of letrozole and GnRH analogue as primary therapy in premenopausal women with ER and PgR positive locally advanced operable breast cancer

Preoperative endocrine therapy is effective in postmenopausal patients with breast cancers expressing oestrogen receptor. We investigated the activity of primary therapy with letrozole in combination with GnRH analogue in premenopausal women with T2-T4 N0-N2 breast cancer, whose tumours expressed oestrogen and progesterone receptors. We measured the expression of molecular factors involved in responsiveness to endocrine agents including ERalpha, EGFR, HER2, MAP kinases (and phosphorylated forms) ER-beta1, both at initial biopsy and at the time of surgery. Thirty-five patients were included and 32 patients were evaluable for response. Sixteen patients (50%, 95% CI 32-68%) obtained a partial response, 16 patients were stable. One patient showed pathological complete response (3%, 95% CI 0-16%). Response was significantly associated with younger age (P<0.05) and a longer duration of treatment (P<0.05). Treatment significantly decreased ERalpha-p-Ser(118) and upregulated ER-beta1, independently of response. No or negligible overexpression of EGFR was observed at baseline or after treatment in this population. Preoperative letrozole and GnRH analogue are effective in premenopausal women. A biological response in terms of downregulation of phosphorylated ERalpha was observed in all patients. Future investigations might focus on treatments of longer duration.

Comparative economic analysis of aromatase inhibitors and tamoxifen in the treatment of hormone-dependent breast cancer

Within the past 2 years three separate groups reported marked improvements in relapse-free survival when trastuzumab was added to adjuvant chemotherapy in patients with HER2-overexpressing breast cancer. Notwithstanding the significance of this molecular target, the discovery of the estrogen receptor (ER) may be of even greater importance. Although tamoxifen has long been considered the hormonal therapy of choice for patients with estrogen-responsive breast cancer, accumulating clinical data suggest the new generation of aromatase inhibitors (AIs) is more effective and less toxic. With the availability of new information, guidelines have been updated and reformulated regarding the use of AIs as first-line hormonal therapy in postmenopausal women with ER-positive breast cancer. This paper, a product of the ongoing advances in oncology, incorporates two distinct, yet important, features of oncology; first, clinical concepts related to hormone-dependent breast cancer and second, pharmacoeconomic evaluation of the antiestrogen tamoxifen and the new generation of antiaromatase agents.

Endocrine therapy for breast cancer: an overview

Endocrine therapy for breast cancer has been established in the adjuvant treatment for primary disease and in the treatment of advanced disease. The ER remains the best predictor of response although other factors exist and need to be identified. Pharmacological manipulation has been replacing ablative procedures. Tamoxifen used to be the most popular agent of choice and promising new agents include the pure anti-oestrogens and the third generation selective aromatase inhibitors. Ongoing and future studies will optimise treatment in established areas and will exploit its potential roles in preoperative use and chemoprevention.

Achievements in systemic therapies in the pregenomic era in metastatic breast cancer

Over the last decades, the introduction of several new agents into clinical practice has significantly improved disease control and obtained some, albeit rare, survival benefits in metastatic breast cancer (MBC). Despite these results, the choice of treatment for the majority of patients is still empirically based, since the only two predictive factors with level 1 evidence for clinical use are hormonal receptor status for endocrine therapy and HER-2 status for trastuzumab therapy. Important improvements in the endocrine therapy of both pre- and postmenopausal women with hormone-responsive disease have been achieved. For premenopausal women, ovarian function suppression with luteinizing hormone-releasing hormone analogs combined with tamoxifen has become the standard treatment, although aromatase inhibitors plus ovarian function suppression are under evaluation. In postmenopausal patients, aromatase inhibitors have proved to be superior to standard endocrine therapies in either first- or second-line treatment and a novel antiestrogen compound, fulvestrant, has been introduced in clinical practice. Chemotherapy remains the treatment of choice for hormone unresponsive or resistant patients. Anthracyclines and taxanes have been used either alone or in combination as first-line chemotherapy, but with the more frequent use of these agents in the adjuvant setting, new standards are needed for first-line chemotherapy, and new and more efficacious treatments are required. In the subgroup of patients with tumors that overexpress HER-2, the use of trastuzumab alone or in combination with chemotherapy has modified the natural history of these tumors, even if only about one out of two patients obtains a clinical response. In this review we summarize the main achievements and the currently available treatment options for patients with MBC.

Luteinizing hormone-releasing hormone agonists in premenopausal hormone receptor-positive breast cancer

Ovarian function suppression for the treatment of premenopausal breast cancer was first used in the late 19th century. Traditionally, ovarian function suppression had been accomplished irreversibly via irradiation or surgery, but analogues of the luteinizing hormone-releasing hormone (LH-RH) have emerged as reliable and reversible agents for this purpose, especially the LH-RH agonists. Luteinizing hormone-releasing hormone antagonists are in earlier stages of development in breast cancer and are not currently in clinical use. Luteinizing hormonereleasing hormone agonists act by pituitary desensitization and receptor downregulation, thereby suppressing gonadotrophin release. Limited information is available comparing the efficacies of the depot preparations of various agonists, but pharmacodynamic studies have shown comparable suppressive capabilities on estradiol and luteinizing hormone. At present, only monthly goserelin is Food and Drug Administration-approved for the treatment of estrogen receptor-positive, premenopausal metastatic breast cancer in the United States. Luteinizing hormone-releasing hormone agonists have proven to be as effective as surgical oophorectomy in premenopausal advanced breast cancer. They offer similar outcomes compared with tamoxifen, but the endocrine combination appears to be more effective than LH-RH agonists alone. In the adjuvant setting, LH-RH agonists versus no therapy reduce the annual odds of recurrence and death in women aged>50 years with estrogen receptor-positive tumors. Luteinizing hormone-releasing hormone agonists alone or in combination with tamoxifen have shown disease-free survival rates similar to chemotherapy with CMF (cyclophosphamide/methotrexate/5-fluorouracil). Outcomes of chemotherapy with or without LH-RH agonists are comparable, though a few trials favor the combination in young premenopausal women (aged<40 years). Adjuvant LH-RH agonists with or without tamoxifen might be as efficacious as tamoxifen alone, and the additional benefit from chemotherapy is unclear. Adequately powered studies are now studying the relative merits of combining adjuvant tamoxifen or aromatase inhibitors with ovarian function suppression, the additional benefits of adding ovarian function suppression to chemotherapy, and the need for adjuvant chemotherapy for women treated with combined ovarian function suppression and anti-estrogen therapy.

Recent perspectives of endocrine therapy for breast cancer

The choice of endocrine therapy for breast cancer depends on the menopausal status and stage of disease. Endocrine therapy remains the first choice and most important component in the treatment of hormone sensitive non-life threatening advanced breast cancer. In premenopausal women with metastatic disease, the combination of a luteinizing hormone-releasing hormone (LH-RH) agonist plus tamoxifen is reasonable as first-line endocrine therapy. In postmenopausal patients with recurrent disease progressing after or during adjuvant tamoxifen, third-generation aromatase inhibitors (AIs) are the preferred first-line endocrine treatment. Many premenopausal and postmenopausal women with hormone responsive breast cancer benefit from sequential use of endocrine therapies at the time of disease progression. Recent clinical trials designs have been implemented, employing AIs as monotherapy in postmenopausal breast cancer patients, as first-line adjuvant therapy, and in sequence either 2-3 or 5 years, with initial tamoxifen. Emerging results from these trials indicate an advantage to patients for any of these strategies, and most international guidelines now suggest the use of an AI in the adjuvant setting in postmenopausal women. The use of endocrine treatment for metastatic and early breast cancer will be reviewed here.

Drug Insight: clinical use of agonists and antagonists of luteinizing-hormone-releasing hormone

This article reviews the clinical uses of agonists and antagonists of luteinizing-hormone-releasing hormone (LHRH), also known as gonadotropin-releasing hormone. In particular, the state of the art treatment of breast, ovarian and prostate cancer, reproductive disorders, uterine leiomyoma, endometriosis and benign prostatic hypertrophy is reported. Clinical applications of LHRH agonists are based on gradual downregulation of pituitary receptors for LHRH, which leads to inhibition of the secretion of gonadotropins and sex steroids. LHRH antagonists immediately block pituitary LHRH receptors and, therefore, achieve rapid therapeutic effects. LHRH agonists and antagonists can be used to treat uterine leiomyoma and endometriosis; furthermore, both types of LHRH analogs are used to block the secretion of endogenous gonadotropins in ovarian-stimulation programs for assisted reproduction. The preferred primary treatment of patients with advanced, androgen-dependent prostate cancer is based on the periodic administration of depot preparations of LHRH agonists; these agonists can be likewise used to treat estrogen-sensitive breast cancer in premenopausal women. LHRH antagonists have been successfully used to treat prostate cancer and benign prostatic hypertrophy. Since receptors for LHRH are present on a variety of human tumors, (notably breast, prostate, ovarian, endometrial and renal cancers), cytotoxic therapy that targets these tumors with hybrid molecules of LHRH might be possible in the near future. Analogs of LHRH are now a well-established means of treating sex-steroid-dependent, benign and malignant disorders.

Identifying menopause in breast cancer patients: considerations and implications

The pivotal role for oestrogen in the aetiology and progression of the majority of breast cancers is well established; consequently, endocrine therapy is an important approach in the treatment of this disease for many women. While tamoxifen has been the mainstay of endocrine therapy for breast cancer for over 30 years, we now have a range of therapeutic manipulations, in particular utilising the aromatase inhibitors (AIs) in post-menopausal women. To date each strategy employing an AI, including primary adjuvant monotherapy, switching from tamoxifen after 2-3 years, and extending adjuvant therapy with an AI after 5 years of tamoxifen, has shown superiority compared with tamoxifen alone; however, AI monotherapy is not suitable for pre- or peri-menopausal women, and therefore, an accurate assessment of the menopausal status of each individual patient is essential. Unfortunately, defining post-menopausal status can be fraught with difficulty, especially when cancer therapy is either recently completed (e.g. chemotherapy), or ongoing (e.g. tamoxifen and/or luteinising hormone-releasing hormone analogues). This paper shall review the definition of menopause in breast cancer patients and explore the issues and implications surrounding such a definition with respect to therapy choice for patient and physician alike.

Combined ovarian ablation and aromatase inhibition as first-line therapy for hormone receptor-positive metastatic breast cancer in premenopausal women: report of three cases

Aromatase inhibitors have become well established for the treatment of postmenopausal women with hormone receptor-positive metastatic breast cancer and for adjuvant hormonal therapy for primary breast cancer. Benefit of aromatase inhibition has not yet been extended to premenopausal women. Ovarian ablation by oophorectomy, ovarian radiation or hormonal suppression is the initial recommended treatment for hormone receptor-positive metastatic breast cancer in premenopausal women. The addition of tamoxifen improves the benefit of ovarian ablation/ovarian suppression. Addition of aromatase inhibitors to luteinizing hormone-releasing hormone analogs has been reported to significantly decrease circulating estrogens and produce tumor responses in only a very small number of patients over the last 15 years. We treated three premenopausal patients with hormone receptor-positive metastatic breast cancer with combined oophorectomy or ovarian irradiation and anastrozole. One patient remained free of progression for 4 years, while the other two remained free of progression for more than 5 and 3 years, respectively. We also note that monthly zoledronic acid for 4 years produced sclerosis of vertebral body metastasis. We conclude that combined ovarian ablation and aromatase inhibition is a feasible treatment modality that deserves more attention and further investigation for hormone receptor-positive metastatic breast cancer in premenopausal women.

Pre-menopausal breast cancer and aromatase inhibitors: Treating a new generation of women

Aromatase inhibitors have revolutionized the treatment of post-menopausal women with hormone receptor positive breast cancer. However, approximately 22% of all cases of breast cancer in North America are diagnosed in women below the age of 50 and a substantial proportion of these women are pre-menopausal. In the pre-menopausal population with hormone receptor positive disease, research on the use of aromatase inhibitors is only beginning to emerge. In this review, the mechanism of action of aromatase inhibitors and the history of endocrine treatment for pre-menopausal breast cancer is briefly presented. Available research to date regarding efficacy and toxicity of aromatase inhibitors in the treatment of pre-menopausal breast cancer and future research directions are also discussed.

Aromatase inhibitors: the next generation of therapeutics for endometriosis?

OBJECTIVE AND DESIGN

To review the role of aromatase inhibitors (AIs) in the treatment of endometriosis.

CONCLUSION(S)

Endometriosis is a common estrogen-dependent disorder that can result in substantial morbidity, including pelvic pain, multiple operations, and infertility. Approximately only half of women with endometriosis get pain relief from existing medical or surgical treatments. Medical treatments usually are directed at inhibiting estrogen action or its production from the ovaries and do not address local estrogen biosynthesis by the aromatase enzyme in endometriotic lesions. A single gene encodes aromatase, which is the final enzyme in the estrogen biosynthesis pathway, and its inhibition effectively eliminates estrogen production. The recently introduced highly specific AIs have successfully treated pelvic pain and significantly reduced the lesion size. In premenopausal women, an AI alone may induce ovarian folliculogenesis, and thus AIs are combined with a progestin, a combination oral contraceptive, or a GnRH analogue. The side-effect profile of AIs administered in combination with an oral contraceptive or a progestin is remarkably benign. We review herein the published clinical evidence for the use of AIs in the treatment of endometriosis.

In vitro detection of cross-resistant and non-cross-resistant agents with fluorouracil for patients with colorectal cancer

BACKGROUND

Fluorouracil-based chemotherapy, such as that with 5-fluorouracil (5-FU)/leucovorin, is standard as first-line chemotherapy for advanced colorectal cancer (CRC) in Japan. However, the best agent for second-line chemotherapy after fluorouracil failure is yet to be determined. This study was undertaken to find an appropriate agent for second-line chemotherapy.

METHODS

Seventy-five tumor specimens from CRC patients with no prior chemotherapy were obtained operatively and their chemosensitivity to five anticancer agents; i.e., 5-FU, mitomycin C (MMC), cisplatin, docetaxel, and an active metabolite of irinotecan (SN-38), was analyzed in an in vitro chemosensitivity test. In this method, the degree of chemosensitivity was expressed as the percent T/C ratio, where T was the total volume of the tumor colonies in the treated group and C was that of the control group. Pearson's correlation coefficients were used to assess the relationship between two agents.

RESULTS

Fifty-eight specimens (colon, 28; rectum, 30) were successfully analyzed. Positive correlations with 5-FU chemosensitivity were verified for the chemosensitivity of MMC, cisplatin, and docetaxel. No correlation with 5-FU chemosensitivity was verified for SN-38 chemosensitivity. Although the functional mechanism of each of the agents differs from that of 5-FU, with the exception of irinotecan, they all had a spectrum closely similar to the 5-FU spectrum.

CONCLUSION

Only irinotecan exhibited a spectrum independent of that of 5-FU, thus indicating that it could be an appropriate agent for second-line chemotherapy after fluorouracil failure.

Trends in endocrine therapy and chemotherapy for early breast cancer: a focus on the premenopausal patient

PURPOSE

The majority of breast cancers are diagnosed at an early stage, and treatment is focused on cure and prolonging disease-free survival. Local therapy (surgery and/or radiation treatment) is standard, along with systemic adjuvant therapy that may effectively prevent or delay relapse and death in early-stage disease. In premenopausal women, adjuvant therapeutic approaches include combination cytotoxic chemotherapy and endocrine therapy. Cyclophosphamide, methotrexate and 5-fluorouracil (CMF) was the established chemotherapy regimen; however, newer regimens have more recently been introduced that may offer some benefit over CMF including anthracycline-containing regimens [e.g. cyclophosphamide, epirubicin and 5-fluorouracil (CEF)], and taxane-containing regimens. For women with oestrogen receptor (ER)-positive disease, a second option is endocrine therapy that aims to suppress mitogenic oestrogen signalling. Until recently, 5 years of tamoxifen was regarded as the standard adjuvant endocrine treatment in ER-positive disease. Ovarian ablation is also effective in premenopausal women, and can be achieved by surgery, radiotherapy, or via the use of a luteinising hormone-releasing hormone analogue such as goserelin. Combining tamoxifen and goserelin treatment provides more effective oestrogen blockade than either drug alone. However, as the third-generation aromatase inhibitors (AIs) have demonstrated improved efficacy over tamoxifen in postmenopausal women with early and advanced disease, combination treatment with goserelin plus an AI may provide optimal oestrogen blockade in premenopausal patients.

CONCLUSIONS

This review assesses the relative merits of chemotherapeutic and endocrine approaches for the treatment of early breast cancer, and summarises relevant ongoing clinical trials, with an emphasis on the premenopausal setting.

Resistance to endocrine therapy in breast cancer

Endocrine therapy is the treatment of choice for patients with breast cancer expressing estrogen receptor (ER) and/or progesterone receptor. The efficacy of endocrine therapy is well established in the prevention, adjuvant and metastatic settings. However, either de novo or acquired resistance is frequently observed. Much effort has been made to elucidate the mechanisms of action underlying resistance to endocrine therapy in breast cancer, and several possible explanations have been suggested. Our previous studies have indicated that combined treatment with an antiestrogen, fulvestrant, and an inhibitor of the HER2 signaling pathway, trastuzumab, or an inhibitor of the HER1 signaling pathway, gefitinib, leads to an additive antitumor effect in breast cancer cells expressing ER and HER2 or HER1, respectively. It has also been suggested that the HER1 or HER2 signaling pathway is upregulated during the development of antiestrogen-resistant growth in breast cancer cells. These findings suggest that signal transduction inhibitors are effective for the treatment of antiestrogen-resistant breast cancer. A hypoxic microenvironment has been shown to promote malignant progression in cancer cells. Our previous study and others have suggested that hypoxia posttranscriptionally reduces ER expression and decreases sensitivity to hormonal agents in breast cancer cells. Our preliminary study has also shown that a hypoxic cytotoxin, tirapazamine, increases ER expression in breast cancer xenografts. Differential antitumor activity of tirapazamine on tumor cells under normoxic or hypoxic conditions may cause this phenomenon. These findings suggest that hypoxic cytotoxins may retard the development of endocrine resistance induced by hypoxia. Molecular mechanisms responsible for endocrine resistance in breast cancer are reviewed and possible therapeutic strategies against this resistance are discussed.

Aromatase inhibitors for therapy of advanced breast cancer

In postmenopausal women with advanced breast cancer, numerous phase III trials have been performed comparing the third-generation non-steroidal aromatase inhibitors (NS-AIs) anastrozole and letrozole and the steroidal AI (S-AI) exemestane in the "first-line" setting against tamoxifen and in the "second-line" setting against megestrol acetate. In both settings, the AIs were at least as efficacious or superior in some endpoints with a preferable toxicity profile including a lower incidence of thrombotic events. Relatively small differences in potency between the three AIs have been identified and it has not been demonstrated that these differences have clinical implications. The recent establishment of the value of AIs in the adjuvant setting for postmenopausal women will impact on their utilization in advanced disease. In premenopausal women the third-generation AIs have not been studied as monotherapy and there is a paucity of data in combination with ovarian function suppression in the advanced disease setting. The main area of future investigations for the AIs in premenopausal women will be in the adjuvant therapy setting in combination with suppression of ovarian function.

Long-term implications of bone loss in breast cancer

Cancer treatment-induced bone loss (CTIBL) is an emerging problem during long-term adjuvant therapy with aromatase inhibitors or ovarian-ablative therapy. CTIBL increases the risk of skeletal complications. Patients receiving adjuvant therapy for breast cancer should receive periodic bone mineral density (BMD) assessments, and those with clinically significant bone loss should be treated with bisphosphonates. Intravenous (i.v.) bisphosphonates (e.g., zoledronic acid) appear to be a very effective treatment for CTIBL. Recently, the Austrian Breast and Colorectal Cancer Study Group 012 trial reported that i.v. zoledronic acid (4 mg every 6 months) maintained BMD in premenopausal women receiving goserelin with either tamoxifen or anastrozole. The Z-FAST and ZO-FAST trials are comparing i.v. zoledronic acid (4 mg every 6 months) up front with letrozole versus initiation when patients exhibit lumbar-spine BMD T-scores > or =2 standard deviations below normal (i.e., T-score < or =-2.0). These studies will provide important insight into the management of CTIBL.