Combined tamoxifen and luteinizing hormone-releasing hormone (LHRH) agonist versus LHRH agonist alone in premenopausal advanced breast cancer: a meta-analysis of four randomized trials

Adjuvant endocrine therapy

Endocrine therapy remains a cornerstone of systemic therapy for breast cancer even though it was first introduced more than a century ago. In the past three decades a large number of randomized trials involving several tens of thousands of patients have been performed to determine the role of endocrine therapy in the adjuvant setting. The results of these studies indicate that hormonal therapy should be considered the standard adjuvant systemic treatment for the majority of patients with invasive breast cancer irrespective of age, menopausal status or tumour stage. This chapter aims to describe the "state of the art" relative to the use of adjuvant endocrine therapy with special focus on a number of salient issues, including: (i) the role of ovarian ablation and luteinising hormone releasing hormone (LHRH) analogues among pre-menopausal patients; (ii) optimal duration of tamoxifen; (iii) adjuvant therapy with third-generation, selective aromatase inhibitors; (iv) predictive biomarkers; (v) side-effects; (vi) combination endocrine therapy; (vii) future development of endocrine therapy.

Sequential hormonal therapy for metastatic breast cancer after adjuvant tamoxifen or anastrozole

The use of adjuvant endocrine therapy in the treatment of hormone receptor-positive, early breast cancer has become important in both pre- and postmenopausal women. Tamoxifen has been the principal adjuvant hormonal therapy in pre- and postmenopausal women with hormone receptor-positive breast cancer for nearly 20 years. Recent data in premenopausal women suggest benefit from ovarian ablation with or without tamoxifen. Early results from the 'Arimidex', Tamoxifen, Alone or in Combination (ATAC) trial have demonstrated that the third-generation, selective aromatase inhibitor (AI) anastrozole ('Arimidex') is a suitable alternative adjuvant therapy for postmenopausal women with hormone receptor-positive disease. After recurrence or relapse on adjuvant endocrine therapy, responses to the sequential use of additional endocrine agents are common. The increase in the number of options now available for adjuvant therapy will have important implications for the selection of the optimal sequence of endocrine agents in the treatment of recurrent breast cancer. Menopausal status is an important factor in determining the endocrine therapy that a patient receives. For premenopausal women, tamoxifen and/or a luteinizing hormone-releasing hormone agonist such as goserelin ('Zoladex') are both options for adjuvant endocrine treatment. After progression on adjuvant and first-line tamoxifen, ovarian ablation is an appropriate second-line therapy. For premenopausal women who have undergone ovarian ablation, the use of third-line therapy with an AI becomes possible. For postmenopausal women, a wide choice of endocrine treatment options is available and an optimal sequence has yet to be determined. Options for first-line therapy of metastatic disease include an AI for women who have received adjuvant tamoxifen or tamoxifen for patients who have received adjuvant anastrozole. In addition, data suggest that fulvestrant ('Faslodex'), a novel estrogen receptor (ER) antagonist that downregulates the ER protein and has no known agonist effects, is a promising therapeutic option that has shown efficacy in the treatment of postmenopausal women with advanced breast cancer. Other agents that may be used in the sequence include the steroidal AI exemestane and the progestin megestrol acetate. The widening range of adjuvant endocrine options therefore represents an opportunity to prolong patient benefits in the treatment of hormone receptor-positive breast cancer, and will require the further refinement of the optimal sequence of endocrine agents for the treatment of recurrent breast cancer.

Adjuvant Chemotherapy Followed by Goserelin Versus Either Modality Alone for Premenopausal Lymph Node-Negative Breast Cancer: A Randomized Trial

BACKGROUND

Although chemotherapy and ovarian function suppression are both effective adjuvant therapies for patients with early-stage breast cancer, little is known of the efficacy of their sequential combination. In an International Breast Cancer Study Group (IBCSG) randomized clinical trial (Trial VIII) for pre- and perimenopausal women with lymph node-negative breast cancer, we compared sequential chemotherapy followed by the gonadotropin-releasing hormone agonist goserelin with each modality alone.

METHODS

From March 1990 through October 1999, 1063 patients stratified by estrogen receptor (ER) status and radiotherapy plan were randomly assigned to receive goserelin for 24 months (n = 346), six courses of "classical" CMF (cyclophosphamide, methotrexate, 5-fluorouracil) chemotherapy (n = 360), or six courses of classical CMF followed by 18 months of goserelin (CMF --> goserelin; n = 357). A fourth arm (no adjuvant treatment) with 46 patients was discontinued in 1992. Tumors were classified as ER-negative (30%), ER-positive (68%), or ER status unknown (3%). Twenty percent of patients were aged 39 years or younger. The median follow-up was 7 years. The primary outcome was disease-free survival (DFS).

RESULTS

Patients with ER-negative tumors achieved better disease-free survival if they received CMF (5-year DFS for CMF = 84%, 95% confidence interval [CI] = 77% to 91%; 5-year DFS for CMF --> goserelin = 88%, 95% CI = 82% to 94%) than if they received goserelin alone (5-year DFS = 73%, 95% CI = 64% to 81%). By contrast, for patients with ER-positive disease, chemotherapy alone and goserelin alone provided similar outcomes (5-year DFS for both treatment groups = 81%, 95% CI = 76% to 87%), whereas sequential therapy (5-year DFS = 86%, 95% CI = 82% to 91%) provided a statistically nonsignificant improvement compared with either modality alone, primarily because of the results among younger women.

CONCLUSIONS

Premenopausal women with ER-negative (i.e., endocrine nonresponsive), lymph node-negative breast cancer should receive adjuvant chemotherapy. For patients with ER-positive (i.e., endocrine responsive) disease, the combination of chemotherapy with ovarian function suppression or other endocrine agents, and the use of endocrine therapy alone should be studied.

Pegylated Liposomal Doxorubicin in the Treatment of Breast Cancer

Anthracyclines, particularly conventional doxorubicin, play an important role in the treatment of breast cancer, both in the adjuvant and metastatic settings. However, the benefits of conventional doxorubicin in terms of antitumor activity are limited by its therapeutic index. Liposomal formulations were developed to increase the therapeutic index of conventional doxorubicin. Pegylated liposomal doxorubicin, the most widely studied liposomal doxorubicin formulation in breast cancer, has been evaluated in > 20 clinical trials. Pegylated liposomal doxorubicin provides tumor-targeted efficacy without many of the toxicities associated with conventional doxorubicin, including myelosuppression, alopecia, nausea and vomiting, and most importantly, cardiac toxicity. As a single agent, pegylated liposomal doxorubicin has demonstrated similar efficacy to that of conventional doxorubicin in patients with metastatic breast cancer. It has also demonstrated efficacy in combination with other agents or modalities, including cyclophosphamide, paclitaxel, docetaxel, gemcitabine, vinorelbine, and hyperthermia. Response rates in patients with metastatic breast cancer receiving pegylated liposomal doxorubicin either alone or in combination regimens range from 27% to 83%, with median survival estimated at 7-20 months. Small studies also suggest a role for pegylated liposomal doxorubicin in the treatment of locally advanced breast cancer. Preliminary results suggest that pegylated liposomal doxorubicin may be safely administered in combination with docetaxel and trastuzumab in patients with HER2-positive disease. Owing to its comparable efficacy and favorable safety profile, pegylated liposomal doxorubicin may be a useful alternative to conventional doxorubicin, as well as other agents commonly used in the treatment of breast cancer.

Current status of endocrine therapy for breast cancer

Endocrine therapy is usually indicated prior to chemotherapy as the first line therapy for metastatic breast cancer patients because of its milder toxicity. Patients who respond to a first-line endocrine therapy have a high chance of responding to a second-line endocrine therapy, and thus the responders to a first-line endocrine therapy would better be treated with second or third-line endocrine therapy. In the adjuvant setting, tamoxifen (antiestrogen) has been proven to improve the prognosis of both pre- and postmenopausal estrogen receptor positive breast cancer patients, and goserelin (LH-RH agonist) has been proven to improve prognosis in premenopausal women comparable to chemotherapy (CMF). Very recently, preliminary results have indicated that anastrozole (aromatase inhibitor) is superior to tamoxifen as adjuvant treatment for estrogen receptor positive postmenopausal breast cancer patients. In addition, the recent success of tamoxifen in a chemoprevention trial seems to have ushered in a new era wherein prevention of breast cancer is much more emphasized than treatment of established breast cancer.

Counting the costs of treatment: the reproductive and gynaecological consequences of adjuvant therapy in young women with breast cancer

As the mortality rate from breast cancer decreases, the issues facing breast cancer survivors are becoming increasingly important. Survivors of all ages may face physical and psychosocial consequences of their diagnosis and treatments. However, the long-term fertility and menopause-related side-effects of adjuvant therapy uniquely affect younger premenopausal breast cancer survivors. This article provides an evidence-based overview of the reproductive and gynaecological impact of breast cancer therapy for premenopausal women diagnosed with breast cancer. The physical and psychosocial implications of premature menopause are presented. Strategies for preserving fertility in selected patients are also discussed. Recent clinical trials strongly indicate that premenopausal women with oestrogen receptor positive tumours should receive endocrine therapy. The increased use of endocrine therapies in younger women raises important questions regarding patient information needs and treatment decision-making.

Levels of absolute survival benefit for systemic therapies of advanced cancer. a call for standards

Research on systemic interventions in patients with advanced stage malignancies should be systematised with an emphasis on the absolute gain in survival for the median patient. Such information is most meaningful with relatively large-scale evidence. Here, we summarise the survival impact of 36 interventions compared against other interventions or no treatment for advanced stage malignancies in meta-analyses of individual patient data or in selected recent (2000-2002) randomised trials with >300 randomised subjects. Although 16 interventions showed a formally statistically significant survival benefit against the comparator arm, this exceeded 3 months in only 7 cases. We propose a standardised categorisation of the median survival prolongation in trials and meta-analyses. Level 0: no proven survival benefit; level I: 0-3 months; level II: >3-6 months; level III: >6-24 months; and level IV: more than 24 months. These standardised levels may be incorporated into clinical practice guidelines for individual care and policy-making.

The use of gonadotrophin-releasing hormone (GnRH) agonists in early and advanced breast cancer in pre- and perimenopausal women

Gonadotrophin-releasing hormone (GnRH) agonists, in particular goserelin ('Zoladex'), are increasingly being used for the treatment of breast cancer in women with functioning ovaries. They act by downregulating pituitary GnRH receptors, thereby suppressing the release of luteinising hormone (LH) and follicle stimulating hormone (FSH), which, in turn, reduce the main source of oestradiol production in the ovaries. GnRH agonists have been shown to be as effective therapeutically as surgical ovarian ablation in pre- and perimenopausal women with advanced breast cancer. The combination of a GnRH agonist such as goserelin with the peripheral oestrogen antagonist, tamoxifen, may be used to produce 'combined oestrogen blockade'. In advanced breast cancer, this regimen prolongs progression-free survival and increases both the response rate and duration relative to the use of a GnRH agonist alone. In patients with early breast cancer, the addition of goserelin to 'standard treatment' (i.e. surgery+/-tamoxifen, chemotherapy or radiotherapy) results in a significant benefit in recurrence-free survival and overall survival. This benefit was most apparent in patients with oestrogen receptor (ER) +ve tumours. Goserelin, when used either alone or in combination with tamoxifen as an adjuvant systemic therapy in women with ER +ve tumours, has been shown in clinical trials to produce recurrence-free survival rates equivalent to cytotoxic chemotherapy such as cyclophosphamide, methotrexate, 5-fluorouracil (CMF). Evidence suggests that at least part of the effect of adjuvant cytotoxic chemotherapy in premenopausal women is produced by ovarian ablation. Endocrine therapy with goserelin or goserelin plus tamoxifen should now be considered a treatment option in the management of premenopausal women with ER +ve early breast cancer.

Determinants and prognoses of locoregional and distant progression in breast cancer

PURPOSE

To describe locoregional and distant progression in a population-based breast cancer sample.

METHODS AND MATERIALS

Between 1978 and 1998, the Munich Cancer Registry evaluated 14,429 patients. The mean follow-up of survivors was 8.3 years. Metastases (MET), local recurrence (LR), and lymph node recurrence (LNR) were considered as outcome measures. The prognostic factor for, and effects of, LR and MET were assessed multivariately by the Cox and dynamic Aalen models.

RESULTS

The LR and MET rate increased with increasing tumor size, with the latter described by pT category. Distant MET occurred earlier than local progression. MET was recorded even earlier for MET alone. The mean time from diagnosis to MET for MET and LR was 54.9, 43.4, 29.4, and 24.7 months and for MET only was 36.5, 31.0, 22.6, and 12.9 months for pT1, pT2, pT3, and pT4, respectively. After MET, survival varied only slightly by pT stage; after LR, a more favorable prognosis, especially for pT1 and pT2, was evident. The prognosis after MET depended mainly on the MET location; 50% of patients with cerebral or nervous system MET survived <1 year and 50% of those with skeletal MET survived >2 years. In the Cox model, the relative risk of LR for MET was 3.0. In the Aalen model, after 30 months, when the hazard rates of MET began to decline, there was still an excess risk of MET after LR.

CONCLUSION

This disease description highlights the importance of long-term observational studies. Empiric evidence that LR is both an indicator for, and in part a cause of, MET has been provided. In the future, the MET location should be reported. Variations in guidelines or health care systems that influence the time to MET and survival after MET through different diagnostic procedures should also be considered.

Adjuvant hormonal therapy

Recently, the guidelines for adjuvant hormonal therapy for primary breast cancer were presented at the National Institute of Health Consensus Development Conference in November 2000 and at the 7th International Conference on Adjuvant Therapy of Primary Breast Cancer in February 2001. Adjuvant hormonal therapy should be offered basically to all patients with tumors expressing estrogen receptor (ER) and/or progesterone receptor (PR), assessed by immunohistochemistry. The consensus statements recommended 5 years of tamoxifen as standard hormonal therapy for both premenopausal and postmenopausal patients with ER and/or PR positive tumors. Ovarian ablation or suppression of ovarian function combined with tamoxifen is a treatment of choice for premenopausal patients with high-risk endocrine-responsive tumors. The selection of hormonal therapies and their combination with chemotherapy should be decided according to the assessment of risk of relapse, side effects, and patients' condition and preference.

Chemotherapy alone versus endocrine therapy alone for metastatic breast cancer

BACKGROUND

Both chemotherapy and endocrine therapy can be used as treatments for metastatic breast cancer.

OBJECTIVES

To review the evidence and determine whether chemotherapy or endocrine therapy has the most beneficial effect on treatment outcomes (survival, response rate, toxicity and quality of life).

SEARCH STRATEGY

The specialised register maintained by the Editorial Base of the Cochrane Breast Cancer Group was searched on 16th September 2002 using the codes for "advanced breast cancer", "chemotherapy" and "endocrine therapy". Details of the search strategy applied by the Group to create the register, and the procedure used to code references, are described in the Group's module on the Cochrane Library.

SELECTION CRITERIA

Randomised trials comparing the effects of chemotherapy alone with endocrine therapy alone on pre-specified endpoints in metastatic breast cancer.

DATA COLLECTION AND ANALYSIS

Data were collected from published trials. Hazard ratios were derived for survival analysis and a fixed effect model was used for meta-analysis. Response rates were analysed as dichotomous variables. Toxicity and quality of life data were extracted where present.

MAIN RESULTS

The primary analysis of overall effect using hazard ratios derived from published survival curves involved six trials (692 women). There was no significant difference seen (HR=0.94, 95%CI 0.79-1.12, p=0.5). A test for heterogeneity was p=0.1. A pooled estimate of reported response rates in eight trials involving 817 women shows a significant advantage for chemotherapy over endocrine therapy with RR=1.25 (1.01-1.54, p=0.04). However the two largest trials showed trends in opposite directions, and a test for heterogeneity was p=0.0018. There was little information available on toxicity and quality of life. Six of the seven fully published trials commented on increased toxicity with chemotherapy, mentioning nausea, vomiting and alopecia. Three of the seven mentioned aspects of quality of life, with differing results. Only one trial formally measured quality of life, concluding that it was better with chemotherapy.

REVIEWER'S CONCLUSIONS

In women with metastatic breast cancer and where hormone receptors are present, a policy of treating first with endocrine therapy rather than chemotherapy is recommended except in the presence of rapidly progressive disease.

Goserelin versus cyclophosphamide, methotrexate, and fluorouracil as adjuvant therapy in premenopausal patients with node-positive breast cancer: The Zoladex Early Breast Cancer Research Association Study

PURPOSE

Current adjuvant therapies have improved survival for premenopausal patients with breast cancer but may have short-term toxic effects and long-term effects associated with premature menopause.

PATIENTS AND METHODS

The Zoladex Early Breast Cancer Research Association study assessed the efficacy and tolerability of goserelin (3.6 mg every 28 days for 2 years; n = 817) versus cyclophosphamide, methotrexate, and fluorouracil (CMF) chemotherapy (six 28-day cycles; n = 823) for adjuvant treatment in premenopausal patients with node-positive breast cancer.

RESULTS

Analysis was performed when 684 events had been achieved, and the median follow-up was 6 years. A significant interaction between treatment and estrogen receptor (ER) status was found (P =.0016). In ER-positive patients (approximately 74%), goserelin was equivalent to CMF for disease-free survival (DFS) (hazard ratio [HR], 1.01; 95% confidence interval [CI], 0.84 to 1.20). In ER-negative patients, goserelin was inferior to CMF for DFS (HR, 1.76; 95% CI, 1.27 to 2.44). Amenorrhea occurred in more than 95% of goserelin patients by 6 months versus 58.6% of CMF patients. Menses returned in most goserelin patients after therapy stopped, whereas amenorrhea was generally permanent in CMF patients (22.6% v 76.9% amenorrheic at 3 years). Chemotherapy-related side effects such as nausea/vomiting, alopecia, and infection were higher with CMF than with goserelin during CMF treatment. Side effects related to estrogen suppression were initially higher with goserelin, but when goserelin treatment stopped, reduced to a level below that observed in the CMF group.

CONCLUSION

Goserelin offers an effective, well-tolerated alternative to CMF in premenopausal patients with ER-positive and node-positive early breast cancer.

Sequencing of hormonal therapy in breast cancer

Hormonal therapy plays an integral role in the management of the majority of women with breast cancer who can be considered to have hormone-dependent breast cancer because of the presence of the molecular predictive markers, estrogen receptor and progesterone receptor. Numerous hormonal agents are available from multiple classes of drugs, including selective estrogen receptor modulators, aromatase inhibitors, progestins, androgens, and luteinizing hormone-releasing hormone analogues. Multiple clinical trials involving these agents have been conducted which permit an evidence-based approach to the development of a sequencing strategy for treatment of women with breast cancer.

Systemic therapy

The systemic treatment of breast cancer is a moving target, reflected by the continuous update of treatment guidelines. Chemotherapy regimens, including the adjuvant role of taxanes and preoperative systemic therapy, continue to be optimized. A major challenge facing researchers and clinicians is how to improve the therapeutic index of present and future therapies, identify patients most likely to benefit from the proposed intervention, and avoid treating those who would be exposed to potential toxicities with minimal gain. Anti-estrogens are a prime example of a targeted therapy with a high therapeutic index. Data are now available on aromatase inhibitors in the adjuvant setting and pure antiestrogens in metastatic disease. The role of targeted antihuman epidermal growth factor receptor 2 therapy in the adjuvant setting is being actively investigated, but this is complicated by the inadequate standardization of human epidermal growth factor receptor 2 expression assays used in clinical practice. A long overdue revision of the breast cancer staging system becomes effective in January 2003, bringing it more in line with current standards of care and facilitating data collection for future outcome analysis of therapeutic interventions. These and other important developments since 2001 are examined in this review.

Chemotherapy-induced amenorrhea and fertility in women undergoing adjuvant treatment for breast cancer

BACKGROUND

The majority of women diagnosed with early-stage breast cancer have an excellent long-term prognosis, but many will undergo temporary or permanent chemotherapy-induced amenorrhea.

METHODS

While breast cancer is more common in older women, about 1 in 200 women under the age of 40 is at risk to develop breast cancer. Many of these women benefit from chemotherapy but are afraid to risk the opportunity to bear children. The authors review the current studies on the impact of adjuvant chemotherapy on amenorrhea and fertility in women with breast cancer.

RESULTS

The likelihood of amenorrhea is based on the specific adjuvant chemotherapy regimen administered and the age of the patient. Future childbirth is a viable option for women treated for breast cancer at an early stage. While the use of tamoxifen as a hormonal therapy in premenopausal breast cancer is now the standard of care, no conclusive data confirm the benefit of GnRH agonists in adjuvant therapy after treatment with chemotherapy followed by tamoxifen.

CONCLUSIONS

As more women over the age of 35 consider pregnancy, fertility issues are becoming important areas of investigation for the adjuvant treatment of breast cancer. Whether chemotherapy-induced amenorrhea has a prognostic effect remains unclear, and further studies are warranted.

Management of premenopausal women with early-stage breast cancer: is there a role for ovarian suppression?

There is an overwhelming body of evidence that adjuvant ovarian ablation/suppression has a favorable impact on survival for premenopausal women with hormone-responsive early-stage breast cancer. This article reviews the randomized controlled trials that provide these data and the indirect evidence suggesting that much of the benefit seen for adjuvant chemotherapy in estrogen receptor-positive patients < 50 years of age is an indirect consequence of a chemical castration. Therefore, carefully selected women may have a choice of ovarian suppression with a gonadotropin-releasing hormone (GnRH) analogue, such as goserelin, as an alternative to chemotherapy, which would allow younger premenopausal women to retain fertility. In addition, if chemotherapy is selected and the patient does not develop permanent amenorrhoea, then additional treatment with a GnRH analogue is indicated.

Ovarian hyperstimulation by LH leads to mammary gland hyperplasia and cancer predisposition in transgenic mice

Many risk factors for breast cancer are associated with hormonally regulated events. Although numerous mouse models of mammary cancer exist, few address the roles of hormones in spontaneous tumor formation. Here we report that transgenic mice that overexpress LH, resulting in ovarian hyperstimulation, undergo precocious mammary gland development. A significant increase in proliferation leads to ovary-dependent mammary gland hyperplasia. Transgenic glands morphologically mimic those of wild-type pregnant mice and expression levels of multiple milk protein genes are comparable with what is observed at d 14 of pregnancy. In addition to sustained hyperplasia, spontaneous mammary tumors were observed with a mean latency of 41 wk, indicating that chronic hormonal stimulation causes mammary cancer. Although hormonally induced, these tumors lack expression of progesterone receptor, suggesting that following initiating events, the tumors may become hormone independent. This mouse model likely holds great potential as a tool for discovery of hormone-mediated mechanisms of breast cancer and identification of future targets for breast cancer prevention and treatment.

Oophorectomy and tamoxifen adjuvant therapy in premenopausal Vietnamese and Chinese women with operable breast cancer

PURPOSE

In 1992, the Early Breast Cancer Trialists' Collaborative Group reported that a meta-analysis of six randomized trials in European and North American women begun from 1948 to 1972 demonstrated disease-free and overall survival benefit from adjuvant ovarian ablation. Approximately 350,000 new cases of breast cancer are diagnosed annually in premenopausal Asian women who have lower levels of estrogen than western women.

PATIENTS AND METHODS

From 1993 to 1999, we recruited 709 premenopausal women with operable breast cancer (652 from Vietnam, 47 from China) to a randomized clinical trial of adjuvant oophorectomy and tamoxifen (20 mg orally every day) for 5 years or observation and this combined hormonal treatment on recurrence. At later dates estrogen- and progesterone-receptor protein assays by immunohistochemistry were performed for 470 of the cases (66%).

RESULTS

Treatment arms were well balanced. With a median follow-up of 3.6 years, there have been 84 events and 69 deaths in the adjuvant treatment group and 127 events and 91 deaths in the observation group, with 5-year disease-free survival rates of 75% and 58% (P =.0003 unadjusted; P =.0075 adjusted), and overall survival rates of 78% and 70% (P =.041 unadjusted) for the adjuvant and observation groups, respectively. Only patients with hormone receptor-positive tumors benefited from the adjuvant treatment. In Vietnam, for women unselected for hormone receptor status, a cost-effectiveness analysis suggests that this intervention costs $350 per year of life saved.

CONCLUSION

Vietnamese and Chinese women with hormone receptor-positive operable breast cancer benefit from adjuvant treatment with surgical oophorectomy and tamoxifen.

Breast cancer risk reduction: strategies for women at increased risk

Breast cancer risk reduction now represents an achievable medical objective. Current interventions include selective estrogen receptor modulators (SERMs), prophylactic surgery, and lifestyle change. For SERMs, current evidence supports tamoxifen use for breast cancer risk reduction whereas raloxifene requires further study. Prophylactic mastectomy and prophylactic oophorectomy, effective in retrospective clinical experiences, should be considered only for women at substantial risk willing to accept the irreversible consequences of these procedures. Although dietary fat intake is under clinical trial evaluation, lifestyle change, including weight loss, dietary change, and increased physical activity, can be recommended based on other health considerations. Use of any intervention requires careful breast cancer risk assessment, risk-benefit calculations, and informed decision making with full patient participation. Future breast cancer risk assessment may incorporate additional biologic measures of estrogen exposure and/or analyses of collected breast cells. Under active evaluation are novel SERMs, aromatase inhibitors/inactivators, gonadotrophin-releasing hormone agonists, retinoids, statins, and tyrosine kinase and cyclooxygenase-2 inhibitors.

Tamoxifen resistance in breast cancer: elucidating mechanisms

Tamoxifen has been used for the systemic treatment of patients with breast cancer for nearly three decades. Treatment success is primarily dependent on the presence of the estrogen receptor (ER) in the breast carcinoma. While about half of patients with advanced ER-positive disease immediately fail to respond to tamoxifen, in the responding patients the disease ultimately progresses to a resistant phenotype. The possible causes for intrinsic and acquired resistance have been attributed to the pharmacology of tamoxifen, alterations in the structure and function of the ER, the interactions with the tumour environment and genetic alterations in the tumour cells. So far no prominent mechanism leading to resistance has been identified. The recent results of a functional screen for breast cancer antiestrogen resis- tance (BCAR) genes responsible for development of tamoxifen resistance in human breast cancer cells are reviewed. Individual BCAR genes can transform estrogen-dependent breast cancer cells into estrogen-independent and tamoxifen-resistant cells in vitro. Furthermore, high levels of BCAR1/pl30Cas protein in ER-positive primary breast tumours are associated with intrinsic resistance to tamoxifen treatment. These results indicate a prominent role for alternative growth control pathways independent of ER signalling in intrinsic tamoxifen resistance of ER-positive breast carcinomas. Deciphering the differentiation characteristics of normal and malignant breast epithelial cells with respect to proliferation control and regulation of cell death (apoptosis) is essential for understanding therapy response and development of resistance of breast carcinoma.

Endocrine-responsive breast cancer and strategies for combating resistance

Deaths from breast cancer have fallen markedly over the past decade due, in part, to the use of endocrine agents that reduce the levels of circulating oestrogens or compete with oestrogen for binding to its receptor. However, many breast tumours either fail to respond or become resistant to endocrine therapies. By understanding the mechanisms that underlie this resistance, we might be able to develop strategies for overcoming or bypassing it.

Chemotherapy versus hormonal adjuvant treatment in premenopausal patients with breast cancer

Comparisons between the effects exerted by adjuvant cyclophosphamide, methotrexate and 5-fluorouracil (CMF)-based polychemotherapy and endocrine treatment in premenopausal breast cancer patients are validly drawn in the presence of steroid hormone receptor responsiveness. First, ovarian ablation still remains to show activity compared with chemotherapy in large patient groups. Second, tamoxifen is at least as active in this cohort and, by comparison, produces a significant effect in mortality reduction. Third, induction of reversible amenorrhoea by LHRH analogue administration has shown comparable effects in terms of recurrence-free survival. Finally, recent European investigations have indicated significant recurrence reductions with LHRH analogue-tamoxifen combination strategies. In conclusion, various endocrine treatment modalities have been substantiated as equiefficient to polychemotherapy. Tamoxifen added to a LHRH analogue further diminishes the recurrence rates and now appears to be a valid treatment alternative. We argue that selection of adjuvant systemic therapy for premenopausal breast cancer patients be increasingly guided by knowledge of the steroid hormone receptor levels.

Combination endocrine therapy in the management of breast cancer

Combination endocrine therapy has long been sought after as a means to better treat breast cancer. Agents that suppress estrogen production are given with agents that suppress estrogenic activity at the cellular level. Historically, these combinations have resulted in initial improvements in response rates, but relapse-free and overall survival were not significantly improved. Also, the increased toxicity seen with these regimens was limiting. New endocrine therapies with more potent activity and less toxicity have led to a resurgence of this idea in the management of breast cancer. Complete estrogen blockade has been compared with single-agent treatments in many different settings. The endocrine effects of this type of therapy are intriguing, but apparently do not readily predict a clinical advantage. The combination of an aromatase inhibitor and an antiestrogen, despite pharmacokinetic interactions, may prove to be beneficial. Results from ongoing trials are eagerly awaited to further address this question in postmenopausal breast cancer patients. For premenopausal breast cancer patients the options are more complex. Clinical outcomes with leutinizing hormone releasing hormone (LHRH) agonists plus aromatase inhibitors are limited to very small phase II studies and are not clearly superior to single-agent therapy. Clinical data in the metastatic setting with premenopausal patients favor the use of an LHRH agonist with tamoxifen over the use of an LHRH agonist alone. However, a similar comparison with tamoxifen alone is lacking with only one trial including this as a treatment arm. Adjuvant therapy with this combined endocrine approach (LHRH agonist plus antiestrogen) has been more extensively studied, but lacks crucial comparisons necessary for making complex treatment decisions. Hopefully, through investigative diligence and ingenuity this issue can be adequately understood. However, many exciting new agents are on the horizon that offer hope to further advance the progress made to date although further confounding the questions already answered.

Premenopausal Breast Cancer

Modern treatment of premenopausal breast cancer is based on well-established prognostic and predictive factors for disease outcome such as nodal status, hormone receptor expression, tumour size, tumour grading and patient age. The development of strategies according to such individual risk profiles has resulted in significant improvements both in overall and disease-free survival. An abundant number of new prognostic and predictive factors in addition to those already mentioned may help to increase our understanding of the biology of breast cancer and to individualize therapy in premenopausal patients. Although less than 10% of patients directly benefit, it is estimated that approximately each year the life of more than 4000 women in Germany will be saved or prolonged by adjuvant treatment. Whether dose intensive modifications and new antineoplastic drugs can improve disease outcome will be clarified when ongoing studies have increased observation time. At present, hormone ablation via surgical, radiotherapeutical or drug-induced castration in addition to selective estrogen response modifiers (SERM), such as tamoxifen, with or without chemotherapy remains the cornerstone of adjuvant treatment in premenopausal patients with breast cancer. In advanced disease, new highly effective hormonal and other target-oriented antineoplastic agents with few adverse effects have been recently introduced. However, overall survival in metastatic disease remains poor, even when intensive or high-dose chemotherapy is used. Special attention must be given to longer follow up and potential toxic long-term adverse effects of therapy when new regimens are applied in clinical trials.

Use of SERMs for the adjuvant therapy of early-stage breast cancer

Tamoxifen was the first in a class of drugs now commonly referred to as selective estrogen receptor modulators or SERMs. SERMs exhibit tissue-specific estrogenic agonist/antagonist activity through their ability to bind to the estrogen receptor alpha (ER) protein and interact with coregulatory proteins, thereby modulating transcription of estrogen target genes. Since its first approval by the United States Food and Drug Administration (FDA) in 1977, tamoxifen has been found to (a) lower the risk of recurrence and death for women with early-stage hormone receptor-positive breast cancer, irrespective of menopausal and node status or use of adjuvant chemotherapy; (b) reduce the risk of invasive breast cancer following breast conservation in women with ductal carcinoma in situ (DCIS); and (c) reduce the risk of breast cancer in high-risk women. Toremifene is the only other SERM approved by the FDA for breast cancer treatment. However, it offers no clear clinical advantage over tamoxifen in the adjuvant or metastatic settings. Several other SERMs are in various phases of clinical development. In addition, strategies to combine SERMs with other endocrine therapy like ovarian suppression or aromatase inhibitors are active areas of investigations. At present, SERMs are recognized as the first targeted and relatively nontoxic medical therapy for women with high-risk or steroid hormone receptor-positive breast cancer.

Systemic therapy

A large body of data on systemic therapy has been presented and published in the past year, including new information on primary risk reduction, patient selection for adjuvant systemic therapy, and anthracycline-analogs. New data on ongoing adjuvant trials (including taxane studies), unpublished updates from the fourth Oxford Overview in September 2000, and provocative data on ovarian ablation were important features of the November 2000 National Institutes of Health Consensus Development Conference on Adjuvant Therapy for Breast Cancer. Important new data on anti-estrogen therapy, including aromatase inhibitors and pure antiestrogens, further expand the role of the oldest targeted breast cancer therapy. Trastuzumab and other novel compounds are being investigated as single-agents and in combination with conventional systemic approaches. Discussions on the long-term effects of adjuvant therapy have taken center stage also. These and other important ongoing developments since 2000 are examined in this review article.