Tamoxifen versus high-dose oral medroxyprogesterone acetate as initial endocrine therapy for patients with metastatic breast cancer: a Piedmont Oncology Association study

Retrospective study on the effectiveness of medroxyprogesterone acetate in the treatment of ER-positive/HER2-negative post-menopausal advanced breast cancer: an additional analysis of the JBCRG-C06 Safari study

BACKGROUND

Only old evidence exists to back up the use of medroxyprogesterone acetate. Therefore, this study aimed to explore the factors that influence the time to treatment failure of medroxyprogesterone acetate in real-world settings as late-line treatment.

METHODS

This was a cohort study that used the database of the Safari study on oestrogen receptor-positive post-menopausal advanced breast cancer (UMIN000015168). We created Kaplan-Meier curves for time to treatment failure with medroxyprogesterone acetate. Further, univariate and multivariate analyses were performed using a Cox hazard model of the clinicopathological factors involved in the time to treatment failure of medroxyprogesterone acetate.

RESULTS

From the 1031 patients in the Safari study, 279 patients were selected as the population for the analysis of effectiveness of medroxyprogesterone acetate monotherapy. In the analysis of medroxyprogesterone acetate by treatment line, the median time to treatment failure was 3.0 months for third-line treatment and 4.1 months for fourth and subsequent treatment lines. In cases where medroxyprogesterone acetate was used as a third-line or later endocrine treatment, multivariate analysis showed that the length of the disease-free interval was correlated with the length of time to treatment failure of medroxyprogesterone acetate (P = 0.004). With medroxyprogesterone acetate monotherapy as the fourth-line or later treatment, 20% of the patients achieved a time to treatment failure of 12 months or longer.

CONCLUSION

In actual clinical practice, patients treated with medroxyprogesterone acetate alone as the fourth or subsequent treatment lines showed a time to treatment failure of 4 months, suggesting that there is merit in using medroxyprogesterone acetate even in late treatment lines, especially in patients with long disease-free interval and those who are difficult to treat using other antineoplastic agents.

Maintenance Therapy with Aromatase Inhibitor in epithelial Ovarian Cancer (MATAO): study protocol of a randomized double-blinded placebo-controlled multi-center phase III Trial

Background

A high percentage of epithelial ovarian cancers (EOC) express the estrogen receptor (ER), which is an ideal target for endocrine therapy. Letrozole is a proven, potent aromatase inhibitor, extensively tested and used in the treatment of ER positive breast cancer. In addition, it seems a potent drug for patients with heavily pre-treated OC as demonstrated in several distinctive settings. However, it has never been evaluated prospectively in a maintenance setting for ovarian cancer after standard of care. The here proposed trial aims to define a population of EOC patients, who would benefit from the effectiveness of the generic agent letrozole, with little expected toxicity and thus beneficial impact on overall quality of life (QoL).

Methods

In this international multicenter randomized, placebo-controlled phase III trial at clinical centers in Switzerland, Germany and Austria, we plan to include 540 patients with primary, newly diagnosed FIGO Stage II to IV and histologically confirmed low- or high-grade serous or endometrioid epithelial ovarian/fallopian tube/peritoneal cancer. Patients are randomized in a 1:1 ratio into two groups: receiving blinded study treatment (letrozole or placebo tablets). When assuming a HR of 0.7, a median PFS of 18 months in the control arm and a median PFS of 25.7 months in the treatment arm, a two-sided alpha level of 5%, 3.5 years recruitment and 1.5 years observation time, we expect 330 events to have occurred within these 5 years in the total cohort yielding a power of 90%. Follow-up data for the whole cohort will be collected for up to 10 years and for the low-grade cancer for up to 12 years.

Discussion

The here proposed randomized phase III trial aims to identify patients with EOC in the maintenance setting, who benefit from the effectiveness of the letrozole, by proving its efficacy whilst maintaining a high standard of QoL due to the limited toxicity expected in comparison to the current alternative drugs on the market for this treatment phase.

Trial registration

This trial is registered at clinicaltrials.gov under the identifier NCT04111978. Registered 02 October 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09555-8.

Local control of bone metastases treated with external beam radiotherapy in recent years: a multicenter retrospective study

BACKGROUND

Over the past decades, remarkable advancements in systemic drug therapy have improved the prognosis of patients with bone metastases. Individualization is required in external beam radiotherapy (EBRT) for bone metastases according to the patient's prognosis. To establish individualized EBRT for bone metastases, we investigated factors that affect the local control (LC) of bone metastases.

METHODS

Between January 2010 and December 2019, 536 patients received EBRT for 751 predominantly osteolytic bone metastases. LC at EBRT sites was evaluated with a follow-up computed tomography. The median EBRT dose was biologically effective dose (BED10) (39.0) (range of BED10: 14.4-71.7 Gy).

RESULTS

The median follow-up time and median time of computed tomography follow-up were 11 (range 1-123) months and 6 (range 1-119) months, respectively. The 0.5- and 1-year overall survival rates were 73% and 54%, respectively. The 0.5- and 1-year LC rates were 83% and 79%, respectively. In multivariate analysis, higher age (≥ 70 years), non-vertebral bone metastases, unfavorable primary tumor sites (esophageal cancer, colorectal cancer, hepatobiliary/pancreatic cancer, renal/ureter cancer, sarcoma, melanoma, and mesothelioma), lower EBRT dose (BED10 < 39.0 Gy), and non-administration of bone-modifying agents (BMAs)/antineoplastic agents after EBRT were significantly unfavorable factors for LC of bone metastases. There was no statistically significant difference in the LC between BED10 = 39.0 and BED10 > 39.0 Gy.

CONCLUSIONS

Regarding tumor-related factors, primary tumor sites and the sites of bone metastases were significant for the LC. As for treatment-related factors, lower EBRT doses (BED10 < 39.0 Gy) and non-administration of BMAs/antineoplastic agents after EBRT were associated with poor LC. Dose escalation from BED10 = 39.0 Gy did not necessarily improve LC.

Optimizing treatment selection, and sequencing decisions for Management of HR-Positive, HER2-Negative advanced breast cancer - Proceedings from breast cancer expert group meeting

PURPOSE

The therapeutic landscape of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (mBC) has evolved considerably with the introduction of newer targeted agents and their combinations with endocrine therapies. In this scenario, optimizing treatment selection and sequencing is daunting for clinicians. The purpose of this review is to provide evidence-based answers to key clinical questions on treatment selection and sequencing for the management of HR + HER2 - mBC.

DESIGN

A panel of nine key opinion leaders from Argentina, Brazil, Colombia, Mexico, Moscow, Singapore, South Korea, Taiwan, and UAE convened in October 2018. They reviewed the literature and formulated answers to clinical questions on optimizing the management of HR + HER2 - mBC.

RESULTS

Evidence-based answers were formulated for: (1) optimal initial treatment choice; (2) ovarian function suppression, optimal endocrine partner, and role of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors (in premenopausal women); (3) better first-line standard of care than aromatase inhibitors; (4) preferred second-line treatment; (5) treatment of oligometastatic disease; (6) factors influencing first-line single-agent endocrine therapy choice; (7) influence of endocrine resistance on treatment selection; (8) optimal maintenance regimen in visceral crisis; and (9) need for a breast cancer registry for patients with HR + HER2 - mBC. The panel also proposed a treatment-sequencing algorithm for the management of HR + HER2 - mBC.

CONCLUSION

The current article will serve as a comprehensive guide for optimizing the management of HR + HER2 - mBC. The proposed breast cancer registry will help identify unmet needs and develop strategic regional policies to help improve access to optimized care for HR + HER2 - mBC.

Leveraging Antiprogestins in the Treatment of Metastatic Breast Cancer

Although incurable, the prognosis for patients with metastatic breast cancer (MBC) has considerably improved with the approvals of multiple targeted and cytotoxic therapies. For hormone receptor-positive (HR+), ie, estrogen receptor and progesterone receptor positive (ER+/PgR+) and human epidermal growth factor receptor-2 negative (ie, ERBB2 gene nonamplified or HER2-) MBC, current approved treatment options include palliative endocrine therapy (ET), cyclin-dependent kinase (CDK 4/6) inhibitors, mTOR inhibitors, and PI3 kinase inhibitors. Most treatments target ER+ disease regardless of PgR status. Although the presence of PgR is crucial for ER+ cell proliferation in both normal and malignant mammary tissue, currently, there are no approved treatments that specifically target PgR. Recent literature has demonstrated the potential of antiprogestins in the treatment of MBC both in preclinical and clinical studies. Antiprogestins, including selective PgR modulators (SPRMs) that act as PgR antagonists, are a promising class of therapeutics for overcoming endocrine resistance in patients who develop activating estrogen receptor 1 (ESR1) and phosphatidylinositol 3-kinase (PI3K) gene mutations after prior endocrine therapy. Herein, we summarize the role of PgR and antiprogestins in the treatment of MBC. Other aspects on the use of functional imaging, clinical trials incorporating novel antiprogestins, and potential treatment combinations to overcome endocrine resistance will be briefly discussed.

Human versus non-human sex steroid use in hormone replacement therapies part 1: Preclinical data

Prior to 2002, hormone replacement therapy (HRT) was considered to be an important component of postmenopausal healthcare. This was based on a plethora of basic, epidemiological and clinical studies demonstrating the health benefits of supplementation with human sex steroids. However, adverse findings from the Women's Health Initiative (WHI) studies that examined the 2 major forms of HRT in use in the US at that time - Premarin (conjugated equine estrogens; CEE) and Prempro (CEE + medroxyprogesterone acetate; MPA), cast a shadow over the use of any form of HRT. Here we review the biochemical and physiological differences between the non-human WHI study hormones - CEE and MPA, and their respective human counterparts 17β-estradiol (E₂) and progesterone (P₄). Preclinical data from the last 30 years demonstrate clear differences between human and non-human sex steroids on numerous molecular, physiological and functional parameters in brain, heart and reproductive tissue. In contrast to CEE supplementation, which is not always detrimental although certainly not as optimal as E₂ supplementation, MPA is clearly not equivalent to P₄, having detrimental effects on cognitive, cardiac and reproductive function. Moreover, unlike P₄, MPA is clearly antagonistic of the positive effects of E₂ and CEE on tissue function. These data indicate that minor chemical changes to human sex steroids result in physiologically distinct actions that are not optimal for tissue health and functioning.

Advances in Endocrine Therapy for Postmenopausal Metastatic Breast Cancer

A majority of breast cancers are hormone receptor (HR) positive and are responsive to various types of hormone manipulation. Endocrine therapy is the preferred first-line therapy for patients with advanced estrogen receptor (ER) positive, HER2-negative breast cancer who do not have symptomatic visceral disease. Endocrine therapy is often continued in the second- and third-line setting, with chemotherapy deferred until tumor becomes endocrine therapy refractory and/or a visceral crisis in imminent. Therapeutic options vary based on clinical presentation and include single-agent therapies such as tamoxifen, aromatase inhibitors and fulvestrant, and combination therapies options. Over the past few years, multiple trials have shown significant improvement in outcomes when endocrine therapy is combined with CDK 4/6 inhibitors or mTOR inhibitors. Improved efficacy comes at a cost of a modest increase in toxicity. Mechanisms of ER resistance have been defined leading to multiple strategies to improve efficacy and overcome resistance. These include the combination therapies options mentioned above and other novel drugs that are in development. This review will summarize the existing literature regarding endocrine therapy in postmenopausal metastatic breast cancer and outline treatment approaches in the first-line metastatic setting and beyond.

Pushing estrogen receptor around in breast cancer

The estrogen receptor-α (herein called ER) is a nuclear sex steroid receptor (SSR) that is expressed in approximately 75% of breast cancers. Therapies that modulate ER action have substantially improved the survival of patients with ER-positive breast cancer, but resistance to treatment still remains a major clinical problem. Treating resistant breast cancer requires co-targeting of ER and alternate signalling pathways that contribute to resistance to improve the efficacy and benefit of currently available treatments. Emerging data have shown that other SSRs may regulate the sites at which ER binds to DNA in ways that can powerfully suppress the oncogenic activity of ER in breast cancer. This includes the progesterone receptor (PR) that was recently shown to reprogram the ER DNA binding landscape towards genes associated with a favourable outcome. Another attractive candidate is the androgen receptor (AR), which is expressed in the majority of breast cancers and inhibits growth of the normal breast and ER-positive tumours when activated by ligand. These findings have led to the initiation of breast cancer clinical trials evaluating therapies that selectively harness the ability of SSRs to 'push' ER towards anti-tumorigenic activity. Our review will focus on the established and emerging clinical evidence for activating PR or AR in ER-positive breast cancer to inhibit the tumour growth-promoting functions of ER.

Steroid Hormone Receptor Positive Breast Cancer Patient-Derived Xenografts

The vast majority of breast cancers are positive for estrogen receptor (ER) and depend on estrogens for growth. These tumors are treated with a variety of ER-targeted endocrine therapies, although eventual resistance remains a major clinical problem. Other steroid hormone receptors such as progesterone receptor (PR) and androgen receptor (AR) are emerging as additional prospective targets in breast cancer. The fundamental mechanism of action of these steroid receptors in gene regulation has been defined mainly by several breast cancer cell lines that were established in the late 1970s. More recently, breast cancer patient-derived xenografts (PDX) have been developed by multiple groups at institutions in several countries. These new models capture the large degree of heterogeneity between patients and within tumors and promise to advance our understanding of steroid hormone receptor positive breast cancer and endocrine resistance. Unfortunately, steroid hormone receptor positive breast cancers are much more difficult than their receptor negative counterparts to establish into sustainable PDX. Herein we discuss the derivation of steroid hormone receptor positive breast cancer PDX, several pitfalls in their genesis, and their utility in preclinical and translational steroid hormone receptor research.

Current Medical Treatment of Patients with Non-Colorectal Liver Metastases: Primary Tumor Breast Cancer

BACKGROUND

(Metastatic) breast cancer is a heterogeneous entity in which every disease subtype requires an individualized systemic treatment approach.

METHODS

We reviewed the currently available data regarding systemic therapy of breast cancer and present a review of historical and current treatment approaches, with the publications cited covering a time span from 1896 to the last ASCO 2015.

RESULTS

Systemic therapy of metastatic breast cancer may include chemotherapy, endocrine therapy, and targeted therapies (e.g. antibody-based approaches). Based on the patient's breast cancer subtype, these agents may be employed alone or in combination. Therefore, characterization of the phenotype of the disease is necessary and may include biopsy of the metastatic site. Novel therapeutic approaches include immunologic therapies as well as PARP, PI3K and CDK 4/6 inhibitors, which are currently under investigation in clinical trials.

CONCLUSION

Systemic therapy of metastatic breast cancer requires complex and individualized treatment approaches that are best offered in an interdisciplinary setting.

Targeted therapies for ER+/HER2- metastatic breast cancer

The majority of breast cancers present with estrogen receptor (ER)-positive and human epidermal growth factor receptor (HER2)-negative features and might benefit from endocrine therapy. Although endocrine therapy has notably evolved during the last decades, the invariable appearance of endocrine resistance, either primary or secondary, remains an important issue in this type of tumor. The improvement of our understanding of the cancer genome has identified some promising targets that might be responsible or linked to endocrine resistance, including alterations affecting main signaling pathways like PI3K/Akt/mTOR and CCND1/CDK4-6 as well as the identification of new ESR1 somatic mutations, leading to an array of new targeted therapies that might circumvent or prevent endocrine resistance. In this review, we have summarized the main targeted therapies that are currently being tested in ER+ breast cancer, the rationale behind them, and the new agents and combinational treatments to come.

Current approaches to the management of Her2-negative metastatic breast cancer

While metastatic breast cancer (MBC) remains incurable, a vast array of active therapeutic agents has provided the opportunity for long-term disease control while maintaining quality of life and physical function. Optimal management of MBC balances a multitude of factors, including a woman's performance status, social support, symptoms, disease burden, prior therapies, and surrogates for tumor biology. Choosing the most appropriate initial therapy and subsequent sequence of treatments demands flexibility as goals and patient preferences may change. Knowledge of the estrogen receptor (ER), progesterone receptor (PR), and Her2 receptor status of the metastatic tumor has become critical to determining the optimal treatment strategy in the metastatic setting as targeted therapeutic approaches are developed. Patients with ER⁺ or PR⁺ breast cancer or both have a wide array of hormonal therapy options that can forestall the use of cytotoxic therapies, although rapidly progressive phenotypes and the emergence of resistance may ultimately lead to the need for chemotherapy in this setting. So-called 'triple-negative' breast cancer - lacking ER, PR, and Her2 overexpression - remains a major challenge. These tumors have an aggressive phenotype, and clear targets for therapy have not yet been established. Chemotherapy remains the mainstay of treatment in this group, but biologically based clinical trials of new agents are critical to developing a more effective set of therapies for this patient population.

The impact of CYP2D6-predicted phenotype on tamoxifen treatment outcome in patients with metastatic breast cancer

Background:

Cytochrome P450 2D6 (CYP2D6) has a crucial role in the metabolic conversion of tamoxifen into the active metabolite endoxifen. In this cohort study, the effect of CYP2D6-predicted phenotype, defined as the combined effect of CYP2D6 genetic variation and concomitant use of CYP2D6-inhibiting medication, on time to breast cancer progression (TTP) and overall survival (OS) in women who use tamoxifen for metastatic breast cancer (MBC) was examined.

Methods:

We selected patients treated with tamoxifen (40 mg per day) for hormone receptor-positive MBC from whom a blood sample for pharmacogenetic analysis (CYP2D6*3, *4, *5, *6, *10 and *41) was available. Patient charts (n=102) were reviewed to assess TTP and OS, and to determine whether CYP2D6 inhibitors were prescribed during tamoxifen treatment.

Results:

OS was significantly shorter in patients with a poor CYP2D6 metaboliser phenotype, compared with extensive metabolisers (HR=2.09; P=0.034; 95% CI: 1.06–4.12). Co-administration of CYP2D6 inhibitors alone was also associated with a worse OS (HR=3.55; P=0.002; 95% CI: 1.59–7.96) and TTP (HR=2.97; P=0.008; 95% CI: 1.33–6.67) compared with patients without CYP2D6 inhibitors.

Conclusion:

CYP2D6 phenotype is an important predictor of treatment outcome in women who are receiving tamoxifen for MBC. Co-administration of CYP2D6 inhibitors worsens treatment outcome of tamoxifen and should therefore be handled with care.

Therapeutic options for metastatic breast cancer

Metastatic breast cancer (MBC) remains an incurable disease despite ongoing therapeutic advances. Recently there has been progress extending the range of available cytotoxic chemotherapy drugs and optimizing their scheduling. In addition, a greater understanding of tumor biology has led to the development of a number of targeted therapies. Several of these newer agents, such as trastuzumab, lapatinib and bevacizumab, have demonstrated activity in combination with chemotherapy and have improved the prognosis of patients with MBC. We hope that further progress elucidating the pathophysiology and biology of MBC will continue to lead to corresponding advances in treatment.

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.

Estrogen receptor modulators and down regulators: optimal use in postmenopausal women with breast cancer

Endocrine treatments have been used in breast cancer since 1896, when Beatson reported on the results of oophorectomy for advanced breast cancer. In the second half of the last century, different endocrine-based compounds were developed and, in this review, the role of the selective estrogen receptor modulators (SERMs) and selective estrogen receptor down regulators (SERDs) in the postmenopausal setting are discussed. Tamoxifen is the most investigated and most widely used representative of these agents, and has been introduced in the advanced disease, in the neoadjuvant and adjuvant setting, and for the prevention of the disease. Its role has been challenged in recent years by the introduction of third-generation aromatase inhibitors that have proven higher activities than tamoxifen with different toxicity patterns. Several other SERMs have been investigated, but none have been clearly superior to tamoxifen. SERDs act as pure estrogen antagonists and should compare favourably to tamoxifen. For the time being, they have been used in the treatment of advanced breast cancers and their role in other settings still needs investigation. The increased use of aromatase inhibitors as first-line endocrine therapy has resulted in new discussions regarding the role that tamoxifen and other SERMs or SERDs may play in breast cancer. The sequencing of endocrine therapies in hormone-sensitive breast cancer remains a very important research issue.

Letrozole in advanced breast cancer: the PO25 trial

Tamoxifen has been a standard first-line endocrine therapy for post-menopausal women with hormone-responsive advanced breast cancer, but more than half of patients fail to respond and time to progression is less than 12 months in responders. The third-generation aromatase inhibitors were developed to provide more effective alternatives to tamoxifen. In the Femara Study PO25, post-menopausal women with advanced breast cancer were randomized to receive letrozole 2.5 mg (n=453) or tamoxifen 20 mg (n=454) given orally daily until progressive disease occurred. Patients were permitted to cross over to the other treatment at progression. In the primary efficacy analysis, median time to progression (TTP) was significantly longer with letrozole than with tamoxifen (9.4 months vs. 6.0 months, respectively; P<0.0001). The objective response rate (ORR) was significantly higher for letrozole than for tamoxifen (32% vs. 21%; P=0.0002). Prospectively planned analyses of the intent-to-treat population showed that letrozole significantly improved overall survival (OS) compared with tamoxifen over the first 24 months of the trial. An exploratory analysis of patients, who did not cross over, indicated a median OS benefit of 14 months for letrozole compared with tamoxifen. Letrozole is the only third-generation aromatase inhibitor that has demonstrated significant improvements in ORR, TTP, and early OS.

Chemotherapy and other systemic therapies for hepatocellular carcinoma and liver metastases

For hepatocellular carcinoma (HCC) that has advanced to the point that it is no longer amenable to local therapies, systemic therapy can be considered in select patients who have a good performance status. No systemic therapy has been clearly shown to improve overall survival compared with supportive care alone, although cancer-related symptoms can sometimes be palliated with therapy and some objective responses are seen. Systemic therapies for HCC include chemotherapy, both intravenous and infused via the hepatic artery, as well as hormonal therapy, immunotherapy, and targeted biologic agents. Colorectal, pancreatic, breast, and lung cancer are some of the most common tumors that metastasize to the liver. Response rates and effect on overall survival as a result of systemic therapy for liver metastases vary widely depending on primary tumor site. Targeted biologic agents are being integrated into standard treatment regimens for all of these cancer types, with variable effects on survival and other outcomes for all affected patients including those with liver metastases.

Beta-interferon and interleukin-2 prolong more than three times the survival of 26 consecutive endocrine dependent breast cancer patients with distant metastases: an exploratory trial

Distant metastases from breast cancer are incurable. In endocrine-responsive patients antiestrogens are commonly administered as first and second line therapy. Regrettably, tumor growth becomes resistant to this relatively innocuous therapy. Beta-interferon was unsuccessfully added to tamoxifen to induce estrogen receptor enhancement. In mice, interleukin-2 added to tamoxifen increased their mutual anti-tumor activities. Nevertheless, no effective clinical application has been developed. We started an exploratory clinical trial based on the association of these immunostimulating cytokines with antiestrogens for first line salvage therapy of hormone dependent breast cancer with distant metastases. Twenty-six consecutive breast cancer patients with distant metastases, 23 of which had metastases at multiple sites, were studied for responsiveness to treatment with first line salvage antiestrogen therapy, combined with beta-interferon and interleukin-2 immuno-therapy. Clinical response and survival were compared with that of 30 consecutive historical control patients treated with antiestrogen therapy alone. Controls showed, as expected, a median duration of response, a median survival time after treatment, and after diagnosis of distant metastases, of 16, 31 and 34 months, respectively. After a mean follow-up of 62+/-36 months (range 17-155), the interval times in the non-control patients were 61 (P<0.001), 101 (P<0.000001) and 106 (P<0.000001) months. Two long-term survivors appeared to be cured after 155 and 94 months from the time of diagnosis with multiple bone metastases. Nineteen of the patients treated with beta-interferon and interleukin-2 have survived. Hormone immuno-therapy was given in an outpatient setting and was very well tolerated. These data suggest that immuno-therapy plays an important role in endocrine-dependent metastatic breast cancer.

Aromatase inhibitors in advanced breast cancer

The third-generation aromatase inhibitors suppress whole-body estrogen production in postmenopausal women with high specificity and potency. In women with hormone-sensitive breast cancer, three of these agents, letrozole, anastrozole, and exemestane, provide an important alternative endocrine therapy to the antiestrogen tamoxifen, which blocks estrogen activation of the estrogen receptor. For treatment of advanced or metastatic breast cancer that has progressed on first-line tamoxifen, all three agents are active. On that basis, they have each been compared with tamoxifen as first-line therapy of advanced breast cancer, in phase III trials. Letrozole was significantly superior to tamoxifen in the primary end point, median time to progression, as well as in response rate and clinical benefit rate, and treatment was well tolerated. Although there was no significant difference in median overall survival, an advantage seen with letrozole for the first 2 years may have been lost because of crossover to the alternate agent at disease progression. Anastrozole was evaluated in two separate trials designed for combined analysis. Overall, anastrozole was at least equivalent to tamoxifen in activity, but clearly superior only for median time to progression in the subgroup of patients with hormone receptor-positive disease. Treatment was generally as well tolerated as tamoxifen. In an early report, exemestane was significantly better than tamoxifen in response rate and median time to progression, with overall survival data not yet available. To date, letrozole appears to be the most effective aromatase inhibitor in the first-line advanced breast cancer setting.

High-dose oral medroxyprogesterone acetate or tamoxifen as adjuvant hormone therapy for node-negative early-stage breast cancer: randomized trial with 7-year update

A randomized adjuvant trial compared tamoxifen 20 mg daily for 5 years with high-dose oral medroxyprogesterone acetate (MPA) 1 g orally for 9 months. One hundred ninety-four patients with histologically proven primary node-negative breast carcinoma were enrolled between December 1990 and October 1996, with 98 patients randomized into the tamoxifen arm and 96 into the MPA arm. At a median follow-up of 86 months, 25 relapses and 13 deaths were recorded. The relapse-free survival rate at 7 years in the tamoxifen arm was 93%, versus 81% in the MPA arm (P = 0.02). The difference was observed in patients with stage T2 disease (100% in the tamoxifen group vs. 64% in the MPA group; P = 0.01), in younger and/or premenopausal patients (in patients < 50 years of age, 100% in the tamoxifen arm vs. 81% in the MPA arm [P = 0.02], and in patients > or = 50 years of age, 90% in the tamoxifen arm vs. 82% in the MPA arm [P = 0.16]). Also, the overall survival rate at 7 years was lower in women < 50 years of age (P = 0.04).

Implications of first-line adjuvant treatment with aromatase inhibitors in recurrent metastatic breast cancer

The role of adjuvant tamoxifen therapy has gone unchallenged until recently. With the introduction of the selective aromatase inhibitors (AIs), the paradigm for treatment of hormone receptor-positive breast cancer in postmenopausal women is changing. New data from randomized clinical trials have shown the impact of the use of an AI compared with tamoxifen or in sequence with tamoxifen. This review will emphasize some of the highlights from these data sets and the limitations of our current knowledge. Finally, we will discuss the implications of the use of nonselective AIs in the adjuvant setting for the patient who develops recurrent metastatic disease.

Letrozole versus tamoxifen in the treatment of advanced breast cancer and as neoadjuvant therapy

Letrozole, a third generation aromatase inhibitor, has been compared with tamoxifen in the treatment of advanced breast cancer and as neoadjuvant therapy. In a first-line trial in advanced disease, 939 post menopausal women were randomised double blind to receive treatment with letrozole 2.5 mg daily or tamoxifen 20 mg daily. Letrozole was significantly superior in terms of median time to progression (9.4 months versus 6.1 months, P=0.0001), objective response (30% versus 20%, P=0.0006), and clinical benefit (49% versus 38%, P=0.0001). Superiority of letrozole was independent of disease site, receptor status, or prior adjuvant anti-oestrogen therapy. In an extended phase of this trial, 200 patients were crossed over to tamoxifen after letrozole, compared with 197 crossed over to letrozole after tamoxifen. Median overall survival was 34 months for letrozole versus 30 months for tamoxifen (not significant). In a similar randomised double-blind neoadjuvant trial, 337 post menopausal patients with large ER/or PgR positive T2-T4 cancers, either requiring mastectomy or locally advanced, were randomised to preoperative letrozole or tamoxifen for 4 months prior to surgery. Overall response was 55% for letrozole versus 36% for tamoxifen (P<0.001). Conservative surgery was possible in 45% of patients treated with letrozole versus 35% with tamoxifen (P=0.022). In both trials, both treatments were well tolerated with no significant differences in side effects. These results indicate that letrozole is more active than tamoxifen both as neoadjuvant therapy and as first-line treatment in advanced disease. They support the importance of current adjuvant trials comparing the two treatments.

Superior efficacy of letrozole versus tamoxifen as first-line therapy for postmenopausal women with advanced breast cancer: results of a phase III study of the International Letrozole Breast Cancer Group

PURPOSE

To compare the efficacy and tolerability of tamoxifen with that of letrozole, an oral aromatase inhibitor, with tamoxifen as first-line therapy in postmenopausal women with advanced breast cancer.

PATIENTS AND METHODS

Nine hundred seven patients were randomly assigned letrozole 2.5 mg once daily (453 patients) or tamoxifen 20 mg once daily (454 patients). Patients had estrogen receptor- and/or progesterone receptor-positive tumors, or both receptors were unknown. Recurrence during adjuvant antiestrogen therapy or within the following 12 months or prior endocrine therapy for advanced disease precluded enrollment. One prior chemotherapy regimen for metastatic disease was allowed. The primary end point was time to progression (TTP). Secondary end points included overall objective response rate (ORR), its duration, rate and duration of clinical benefit, time to treatment failure (TTF), overall survival, and tolerability.

RESULTS

TTP was significantly longer for letrozole than for tamoxifen (median, 41 v 26 weeks). Treatment with letrozole reduced the risk of progression by 30% (hazards ratio, 0.70; 95% confidence interval, 0.60 to 0.82, P =.0001). TTP was significantly longer for letrozole irrespective of dominant site of disease, receptor status, or prior adjuvant antiestrogen therapy. Similarly, TTF was significantly longer for letrozole (median, 40 v 25 weeks). ORR was higher for letrozole (30% v 20%; P =.0006), as was the rate of clinical benefit (49% v 38%; P =.001). Survival data are currently immature and not reported here. Both treatments were well tolerated.

CONCLUSION

Letrozole was significantly superior to tamoxifen in TTP, TTF, ORR, and clinical benefit rate. Our results support its use as first-line endocrine therapy in postmenopausal women with advanced breast cancer.

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

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Systematic reviews of chemotherapy and endocrine therapy in metastatic breast cancer

Metastatic breast cancer is incurable but often responsive to treatment. There is little evidence-based consenus on when to use which treatments, in what combination and for how long. Systematic reviews were performed on 12 prospectively defined, clinically relevant research questions to support the development of evidence-based clinical practice guidelines. A comprehensive search of Medline from 1966 to 1996 identified over 1800 controlled trials. Eligibility and data extraction were performed independently by two blinded reviewers. Trial results were summarised by ratios of median survivals (RMS) and P -values for survival curve comparisons with meta-analysis by weighted combination of these statistics. Sixty-five publications reporting 97 treatment comparisons were included. There was moderate evidence that more rather than fewer cycles of chemotherapy improved survival (RMS:1.23, P -0.01). The evidence did not support: higher rather than lower doses of chemotherapy (or of endocrine therapy); any one class of endocrine agent over all others; multiple endocrine agents over a single agent; or, combined chemotherapy and endocrine therapy over either single modality. Only six trials assessed quality of life revealing better quality of life with more rather than fewer cycles of chemotherapy and with standard rather than lower doses of chemotherapy. These systematic reviews reveal counterintuitive evidence useful to everyday practice, in particular that more rather than fewer cycles of chemotherapy lead to better quality of life and longer survival.

New Treatment Strategy for Bone Metastases from Breast Cancer

Breast cancer patients frequently develop bone metastasis. Parathyroid hormone-related protein, an osteoclast activating factor, might be necessary for tumorto erode bone and grow at skeletal site. Bisphosphonates have an affinity for bone and are potent inhibitors of osteoclastic bone resorption. In light of this,53 patients with bone metastasis from breast cancer were treated with chemoendocrine(mainly high-dose medroxyprogesterone acetate as the endocrine therapy) therapy + bisphosphonate (pamidronate, Aredia (R)). During the previous 6 years (median 27 months), 53 breast cancer patients with bone metastasis were treated with pamidronate + chemoendocrine therapy. The regimen consisting of pamidronate + chemoendocrine agent was administered to 27 patients as a post relapse first-line regimen and to the remaining 26 cases, which failed first- or second-line treatment as a second or third line regimen. As a result of the combination therapy, sclerotic changes were observed in the osteolytic lesions in 31 of the 53 patients (59%). The effect on the osteolytic lesions did not correlate with the duration of disease free interval, estrogen receptor (ER) status, presence/absence of previous therapy or number of " hot spot(s) ] on bone scintigraphy. Lessening of pain from the bone metastasis was achieved in 83% of the patients after 3 months of pamidronate administration. Pamidronate + chemoendocrine therapy seems highly promising.

Failure of megestrol acetate to reverse tamoxifen induced endometrial neoplasia: two case reports

Tamoxifen's agonist effect on the endometrium has been associated with an increased incidence of endometrial carcinoma. It has been suggested that this agonist effect may be averted by the concomitant use of a progestational agent. We report two patients with breast cancer receiving tamoxifen who developed endometrial carcinoma and atypical endometrial hyperplasia, respectively. In one patient, this occurred despite the use of concomitant megestrol acetate. In the other patient, tamoxifen-associated endometrial hyperplasia persisted and progressed despite cessation of tamoxifen and initiation of megestrol acetate therapy. These cases may have implications for strategies to avert tamoxifen induced endometrial neoplasia.

Androgen receptor agonist activity of the synthetic progestin, medroxyprogesterone acetate, in human breast cancer cells

Medroxyprogesterone acetate (MPA), which is frequently used as second line hormonal therapy for the treatment of metastatic breast cancer, binds with high affinity to the progesterone receptor (PR). However, the androgenic side-effects of MPA suggest that it may also activate androgen receptor (AR) regulated pathways. Treatment of the human breast cancer cell lines MDA-MB-453, ZR-75-1 and T47-D with high dose (100 nM) MPA resulted in 26-30% inhibition of cell growth, which was partially reversed by co-treatment with a 10-fold excess of the synthetic antiandrogen, anandron. Scatchard analysis demonstrated specific, high affinity (non-PR) binding of [3H]MPA to cytosols prepared from the PR-/AR+ MDA-MB-453 and PR+/AR+ ZR-75-1, but not the PR-/AR- BT-20 breast cancer cell lines. Competition of [3H]MPA binding to MDA-MB-453 cytosols by equimolar concentrations of androgens (5alpha-dihydrotestosterone (DHT), R1881) and the antiandrogen, anandron was consistent with binding of MPA to the AR. In ZR-75-1 cell cytosol fractions, DHT, R1881 and anandron only partially competed out [3H]MPA binding, suggesting that androgens displace [3H]MPA binding to AR but not to PR. Induction by MPA of AR transactivation was demonstrated in MDA-MB-453 and ZR-75-1 cells, and in the CV-1 cell line transfected with a full-length AR. In these cell lines the increased activity of the androgen responsive reporter gene (MMTV-CAT) by 1 nM MPA was fully (MDA-MB-453, CV-1) or partially (ZR-75-1) inhibited by co-culture with 1 microM anandron. These findings indicate that MPA is an AR agonist and suggest that the in vivo effects of MPA in breast cancer patients may in part be mediated by the AR.

Suppression of parathyroid hormone-related protein messenger RNA expression by medroxyprogesterone acetate in breast cancer tissues

The level of parathyroid hormone-related protein (PTHrP) expressed in breast cancer tissue is closely related to the incidence of bone metastasis. We examined the PTHrP mRNA expression in breast cancer tissues by coamplification polymerase chain reaction (PCR) in mole ratio to internal standard beta-actin mRNA. The PTHrP expression was higher in premenopausal patients than in postmenopausal patients (P < 0.05). More pronounced difference by menopause found in estrogen receptor (ER) positive groups (P < 0.001) indicated that the PTHrP expression in breast cancer tissue is hormonally regulated and might be altered by endocrine agents. To clarify the changes of PTHrP expression by endocrine therapy of breast cancer, we measured PTHrP expression in the breast cancer tissue incubated for 24 h with 1 x 10(-8) M of estradiol (E2), 1 x 10(-6) M of tamoxifen (TAM) and 1 x 10(-5) M of medroxyprogesterone acetate (MPA). The PTHrP expression was decreased significantly by MPA (P < 0.005), while E2 and TAM did not change the PTHrP expression. Progesterone receptor (PgR) mRNA expression was also examined to confirm that the breast cancer tissue responds to E2 and TAM. The results were well compatible with the better therapeutic effect of MPA reported for the treatment of breast cancer with bone metastases. As a potential candidate for the receptor that mediates the suppressive effect of MPA, androgen receptor (AR) is suggested most probable. Present results also demonstrated that the clinical response of individual tumors is closely associated with the early in vitro changes of gene expression detected in the cancer specimen.

Endocrine therapy in metastatic breast cancer

Endocrine therapy represents a mainstay of effective, minimally toxic, palliative treatment for metastatic breast cancer. Research focusing on the mechanism of action of endocrine agents will provide new insights leading to new hormonal approaches in breast cancer treatment. Development of new agents, especially the 'pure' antiestrogens, is of great interest. Combining endocrine therapy with biologic agents, especially antiproliferative compounds, may lead to more effective treatment in the adjuvant as well as the advanced setting. Tables 4 and 5 summarize response rates to the different groups of endocrine agents used in metastatic breast cancer and doses of commonly used agents, respectively. At present, tamoxifen is the drug of choice as first-line endocrine therapy for metastatic breast cancer with no or minimal symptoms in premenopausal or postmenopausal women. Second-line therapy usually consists of megace. Aromatase inhibitors may be used as second- or third-line therapy in postmenopausal women. In premenopausal women, LHRH analogues are a reasonable choice. The other hormonal agents may be beneficial as salvage therapy. More effective endocrine approaches are under development.

Formestane versus megestrol acetate in postmenopausal breast cancer patients after failure of tamoxifen: a phase III prospective randomised cross over trial of second-line hormonal treatment (SAKK 20/90). Swiss Group for Clinical Cancer Research (SAKK)

The aim of the study was to compare efficacy and tolerability of the new aromatase inhibitor formestane (Lentaron) with megestrol acetate (Megestat) (MGA) in postmenopausal patients with advanced breast cancer. 179 patients were randomised to receive either 250 mg formestane intramuscularly biweekly or MGA 160 mg orally daily. 51% of the patients had received tamoxifen as adjuvant treatment; 73% of the patients had positive and 16% unknown oestrogen receptor values. The response rate was 17% in both treatment arms (95% confidence interval 10-26% for formestane and 10-27% for MGA). Disease stabilisation > or = 6 months was seen in 25% of the formestane and 22% of the MGA patients. Time to treatment failure was 120 days in the formestane arm and 111 days in the MGA arm. There was no significant difference between the treatments with regard to response rate and time to treatment failure. Overall toxicity was similar in both arms, but weight gain > 3 kg (P = 0.081) and severe cardiovascular toxicity (P = 0.044) were more frequently observed with MGA, e.g. deep vein thrombosis 0/90 formestane versus 5/81 MGA cases (P = 0.022). Formestane was associated with worsening of hot flushes/sleeping problems (P = 0.051) and mild leucopenia (P = 0.004). In our study, formestane and MGA showed similar antineoplastic activity as second-line hormonal treatment for advanced breast cancer. Both drugs have a specific toxicity profile. MGA was associated with significantly more severe cardiovascular toxicity and weight increase than formestane.

Tamoxifen as initial endocrine therapy for metastatic breast cancer: long term follow-up of two Piedmont Oncology Association (POA) trials

PURPOSE

To examine the outcomes of endocrine naive patients treated with tamoxifen as initial endocrine therapy for metastatic breast cancer. Data were obtained from the long-term follow-up of two previously published randomized trials.

PATIENTS AND METHODS

All patients received tamoxifen 20 mg po in a single daily dose. Eligibility required patients to be age > or = 18, performance status 0-3, and estrogen or progesterone receptor positive or unknown. Patients were ineligible if they had any prior endocrine therapy in either the adjuvant or metastatic setting.

RESULTS

156 patients have been followed for a median of 8.3 years. Median age was 61 years, 83% were > or = 50 years, 84% performance status of 0-1, 43% were both ER and PR positive, 33% had prior chemotherapy, 62% had a disease-free interval of > 2 years, and 59% had only one metastatic site. The complete (14%) and partial (6%) response rate for 147 evaluable patients was 20% (95% CI for CR + PR of 14-27%). Multivariate analysis revealed that improved response was related to soft tissue involvement and positive PR status. The majority of patients with soft tissue, nodal or lung metastases had responses noted within three months. Median time to disease progression was 6.7 months. Multivariate analysis revealed that older patients, those with one metastatic site and those with positive PR status had the longest time to progression. Median survival was 27.2 months. Better performance status, fewer metastatic sites and being PR positive were associated with significantly improved survival.

CONCLUSION

The patient population in this series is not likely to be studied in future trials because of the wide use of tamoxifen in the adjuvant setting. In a small percentage of patients with metastatic breast cancer, tamoxifen therapy is associated with prolonged remission and survival. Pretreatment characteristics can help identify such patients.

First-line fadrozole HCI (CGS 16949A) versus tamoxifen in postmenopausal women with advanced breast cancer. Prospective randomised trial of the Swiss Group for Clinical Cancer Research SAKK 20/88

BACKGROUND

In a phase III randomized trial, we compared the effectiveness and tolerability of fadrozole (CGS 16949A), a non-steroidal aromatase inhibitor, to tamoxifen as first-line endocrine therapy in postmenopausal women with advanced breast cancer.

PATIENTS AND METHODS

Two hundred twelve eligible patients were randomized to receive tamoxifen 20 mg daily, or fadrozole 1 mg twice daily orally until disease progression or the advent of undue toxicity. The treatments were to be discontinued upon disease progression.

RESULTS

Prognostic factors were well balanced between the treatment groups, except for sites of metastatic disease. Fadrozole-treated patients had significantly more visceral, especially liver, involvement and less bone-dominant disease. Response rates for fadrozole and tamoxifen were similar, 20% and 27% (95% Confidence Limits (CL): 13%-29% and 21%-35%), respectively. Time to treatment failure was longer in patients randomized to tamoxifen (8.5 months for tamoxifen vs. 6.1 months for fadrozole), but did not reach statistical significance after adjustment for prognostic factors (P = 0.09). Fadrozole, for which a significantly lower percentage of clinically relevant toxic effects (WHO toxicity grade > or = 2) was recorded (27% vs. 13%, respectively; P = 0.009), was better tolerated than tamoxifen. Severe cardiovascular events including 3 fatalities were seen only in patients treated with tamoxifen. Eighty-two patients crossed over to tamoxifen and 66 patients to fadrozole. Crossover endocrine therapy led to response or stable disease in 64% of the patients. The overall survival times of the two treatment groups were similar.

CONCLUSIONS

Fadrozole and tamoxifen showed similar efficacy as first-line treatments in postmenopausal patients with advanced breast cancer. Fadrozole was significantly better tolerated and may therefore be an appropriate alternative to tamoxifen, especially for patients predisposed to thromboembolic events.