Phase III randomized trial of toremifene vs tamoxifen in hormonodependant advanced breast cancer

Beyond the median: Estimating survival times for patients starting endocrine therapy for estrogen receptor-positive, metastatic breast cancer from recent randomized trials

AIM

To estimate scenarios for survival for patients with estrogen receptor (ER) positive, metastatic breast cancer (MBC) and to help communicate prognosis to patients starting endocrine therapy (ET) METHODS: We searched for randomized trials of ET for ER-positive MBC and extracted the following percentiles (representative survival scenarios) from each overall survival (OS) curve: 90th (worst-case), 75th (lower-typical), 50th (median), 25th (upper-typical), and 10th (best-case). We then assessed the accuracy of estimating these percentiles for each OS curve by multiplying the median OS by four simple multiples: 0.25 (to estimate the 90th percentile), 0.5 (75th), 2 (25th), and 3 (10th). Estimates were deemed accurate if it fell within 0.75-1.33 times the actual value.

RESULTS

We identified 25 trials with 10,566 patients. The median OS (interquartile range) was: 61.3 months (53.4-64.8) for first-line ET with cyclin-dependant kinase 4/6 inhibitors (four treatment groups); 42.6 months (40.9-50.4) for first-line ET alone (21 treatment groups) and 29.2 months (24.8-33.4) for subsequent line ET (19 treatment groups). Simple multiples of the median OS accurately estimated the 90th percentile in 80%; 75th percentile in 93%; and 25th percentile in 76% of curves. The 10th percentile was only available for four OS curves and could not be evaluated.

CONCLUSION

Simple multiples of the median OS are a helpful and accurate method to assist in estimating and discussing scenarios for survival for MBC patients starting ET. Longer follow-up of trials is required to help clinicians estimate the best-case scenario.

Computer-Aided Ligand Discovery for Estrogen Receptor Alpha

Breast cancer (BCa) is one of the most predominantly diagnosed cancers in women. Notably, 70% of BCa diagnoses are Estrogen Receptor α positive (ERα+) making it a critical therapeutic target. With that, the two subtypes of ER, ERα and ERβ, have contrasting effects on BCa cells. While ERα promotes cancerous activities, ERβ isoform exhibits inhibitory effects on the same. ER-directed small molecule drug discovery for BCa has provided the FDA approved drugs tamoxifen, toremifene, raloxifene and fulvestrant that all bind to the estrogen binding site of the receptor. These ER-directed inhibitors are non-selective in nature and may eventually induce resistance in BCa cells as well as increase the risk of endometrial cancer development. Thus, there is an urgent need to develop novel drugs with alternative ERα targeting mechanisms that can overcome the limitations of conventional anti-ERα therapies. Several functional sites on ERα, such as Activation Function-2 (AF2), DNA binding domain (DBD), and F-domain, have been recently considered as potential targets in the context of drug research and discovery. In this review, we summarize methods of computer-aided drug design (CADD) that have been employed to analyze and explore potential targetable sites on ERα, discuss recent advancement of ERα inhibitor development, and highlight the potential opportunities and challenges of future ERα-directed drug discovery.

Progression-Free Survival and Time to Progression as Real Surrogate End Points for Overall Survival in Advanced Breast Cancer: A Meta-Analysis of 37 Trials

BACKGROUND

Progression-free survival (PFS) and time to progression (TTP) have been reported to correlate with overall survival (OS) in several cancer types. To our knowledge, however, the correlation between them is unclear.

METHODS

A literature-based meta-analysis was performed to assess whether PFS and TTP can be considered reliable surrogate end points for OS in a phase 3 clinical trial of advanced breast cancer (ABC). The median hazard ratios of PFS/TTP and OS were analyzed by determining their nonparametric Spearman rank correlation coefficients (Rs).

RESULTS

A total of 37 trials with 38 treatment arms and 14,966 patients were selected for analysis. The Rs between the median PFS/TTP and OS was 0.405 (95% confidence interval [CI], 0.191-0.582; P = .003), and the correlation coefficient between the hazard ratios of PFS/TTP and OS was 0.555 (95% CI, 0.277-0.748; P = .003). PFS/TTP was closely correlated with OS in the trials of targeted therapy-based treatment (Rs = 0.872; 95% CI, 0.619-0.962; P = .0001) and of PFS/TTP or OS benefit (Rs = 0.753 and Rs = 0.821, respectively) for ABC.

CONCLUSIONS

Both PFS and TTP can be considered valid surrogate end points for OS in the trials of targeted therapy-based treatments and clinical benefits for ABC. Further research is necessary to clarify the surrogacy of PFS/TTP for OS in other trials of targeted therapy-based treatments for ABC.

Estrogen receptor agonists/antagonists in breast cancer therapy: A critical review

Estrogens display intriguing tissue selective action that is of great biomedical importance in the development of optimal therapeutics for the prevention and treatment of breast cancer. There are also strong evidences to show that both endogenous and exogenous estrogens are involved in the pathogenesis of breast cancer. Tamoxifen has been the only drug of choice for more than 30years to treat patients with estrogen related (ER) positive breast tumors. There is a need therefore, for identifying newer, potential and novel candidates for breast cancer. Keeping this in view, the present review focuses on selective estrogen receptor modulators and estrogen antagonists such as sulfatase and aromatase inhibitors involved in breast cancer therapy. A succinct and critical overview of the structure of estrogen receptors, their signaling and involvement in breast carcinogenesis are herein described.

Ospemifene: a first-in-class, non-hormonal selective estrogen receptor modulator approved for the treatment of dyspareunia associated with vulvar and vaginal atrophy

Ospemifene is a selective estrogen receptor modulator (SERM) approved for the treatment of dyspareunia associated with vulvar and vaginal atrophy (VVA) due to menopause. As the first non-hormonal treatment for this indication, the approval of ospemifene represents a significant milestone in postmenopausal women's health. Ospemifene is a triphenylethylene similar in chemical structure to tamoxifen and toremifene. Consistent with other SERMs such as tamoxifen, toremifene, and raloxifene, ospemifene possesses a distinctive mix of estrogenic and antiestrogenic tissue-specific effects in bone, breast tissue, serum lipids, and the vagina. Among the approved SERMs, ospemifene is the only agent with a nearly full estrogen agonist effect on the vaginal epithelium while having neutral to slight estrogenic effects in the endometrium, making ospemifene uniquely suited for the treatment of dyspareunia associated with VVA, also known as atrophic vaginitis, which affects up to 50% of postmenopausal women. This review begins with a brief history of the discovery of ospemifene, its mechanism of action, and its preclinical development, with an emphasis on its tissue-specific effects on bone, breast, uterus and endometrium, serum lipids and vagina. A brief discussion on the genotoxicity of ospemifene compared to tamoxifen and toremifene is included. The focus then shifts to the clinical development of ospemifene from Phase I through Phase III. We will close with the FDA approval of ospemifene and a justification of the future clinical evaluation of ospemifene as a potential breast cancer chemopreventive agent, where several preclinical studies in different rodent breast cancer models strongly suggest ospemifene is as effective as tamoxifen.

Atypical McMurry cross-coupling reactions leading to a new series of potent antiproliferative compounds bearing the key [ferrocenyl-ene-phenol] motif

In the course of the preparation of a series of ferrocenyl derivatives of diethylstilbestrol (DES), in which one of the 4-hydroxyphenyl moieties was replaced by a ferrocenyl group, the McMurry reaction of chloropropionylferrocene with a number of mono-aryl ketones unexpectedly yielded the hydroxylated ferrocenyl DES derivatives, 5a–c, in poor yields (10%–16%). These compounds showed high activity on the hormone-independent breast cancer cell line MDA-MB-231 with IC₅₀ values ranging from 0.14 to 0.36 µM. Surprisingly, non-hydroxylated ferrocenyl DES, 4, showed only an IC₅₀ value of 1.14 µM, illustrating the importance of the hydroxyethyl function in this promising new series. For comparison, McMurry reactions of the shorter chain analogue chloroacetylferrocene were carried out to see the difference in behaviour with mono-aryl ketones versus a diaryl ketone. The effect of changing the length of the alkyl chain adjacent to the phenolic substituent of the hydroxylated ferrocenyl DES was studied, a mechanistic rationale to account for the unexpected products is proposed, and the antiproliferative activities of all of these compounds on MDA-MB-231 cells lines were measured and compared. X-ray crystal structures of cross-coupled products and of pinacol-pinacolone rearrangements are reported.

High-dose toremifene for fulvestrant-resistant metastatic breast cancer: a report of two cases

INTRODUCTION

Hormone receptor (HR)-positive metastatic breast cancer (MBC) is usually treated with hormone therapy. In postmenopausal females, aromatase inhibitors (AIs) are usually used as first-line therapy, and fulvestrant is used subsequently. The optimal treatment beyond fulvestrant has not been established. We experienced two cases in which high-dose toremifene (hdTOR) was effective after the failure of AIs and fulvestrant.

CASE 1

A 73-year-old female with HR-positive left breast cancer (T2N1M0) underwent preoperative chemotherapy and mastectomy with axillary dissection. Computed tomography (CT) revealed liver tumors in S7 (23 mm) and S8 (25 mm) during adjuvant letrozole therapy, so fulvestrant was started. The tumors initially decreased in size (23 and 22 mm), but then progressed (36 and 25 mm). Treatment was changed to hdTOR, and the tumors shrunk to 26 mm (S7) and 24 mm (S8), and she was stable for 6 months while receiving hdTOR.

CASE 2

An 81-year-old female with HR-positive left breast cancer (T2N1M0) underwent left mastectomy and axillary dissection. CT revealed liver tumors in S7 (20 mm) and S8 (11 mm) during adjuvant letrozole therapy, so fulvestrant treatment was started. The tumor in S7 shrunk (13 mm), but the tumor in S8 slightly progressed (13 mm), and both tumors progressed (14 and 18 mm) after 6 months. Treatment was changed to hdTOR, and the tumors slightly shrunk (12 and 14 mm) after 6 months. hdTOR has been continued for 9 months.

CONCLUSION

hdTOR was effective for MBC after multiple hormone therapies, likely because it acts via a different mechanism of action.

Effects of toremifene versus tamoxifen on breast cancer patients: a meta-analysis

Toremifene and tamoxifen are both selective estrogen receptor modulators used in the treatment of breast cancer patients. Therefore, we carried out a meta-analysis to achieve a more precise evaluation of the effects of toremifene versus tamoxifen on breast cancer patients, including the efficacy and safety, and the effects on the uterus, lipids, and bone. Comprehensive literature searches were conducted using the electronic databases and reference lists to include randomized controlled trials (RCTs) that compared toremifene with tamoxifen for breast cancer patients. Two reviewers independently selected studies and abstracted data. Data were analyzed by Review Manager, version 5.0. Twenty-three trials (7242 patients) were included. For early stage breast cancer, toremifene was associated with higher 5-year survival rates (OR 1.25, 95 % CI 1.04, 1.50), more vaginal discharge (OR 1. 32, 95 % CI 1.01, 1.73), a greater decrease in serum triglyceride levels (SMD -1.01, 95 % CI -1.89, -0.14), a smaller decrease in LDL cholesterol levels (SMD 0.45, 95 % CI 0.07, 0.84) and in bone mineral density in Ward's triangle (SMD -0.36, 95 % CI -0.71, -0.01), and a greater increase in HDL cholesterol levels (SMD 0.43, 95 % CI 0.08, 0.77) than tamoxifen. For advanced breast cancer patients, toremifene was associated with more vaginal bleeding (OR 0.45, 95 % CI 0.26, 0.80) and a greater decrease in serum triglyceride levels (SMD -1.15, 95 % CI -1.90, -0.39) than tamoxifen. Available evidence showed that toremifene could be an alternative option to tamoxifen for both early and advanced breast cancer patients. However, the methodological quality of the included studies was low. More rigorous RCTs are needed to confirm the results of this meta-analysis in the future.

Phase III randomized trial of toremifene versus tamoxifen for Japanese postmenopausal patients with early breast cancer

BACKGROUND

Toremifene, a selective estrogen receptor modulator, is used as adjuvant therapy for postmenopausal patients with breast cancer in Japan. For Japanese patients, however, only limited data are available on the efficacy and safety profile of toremifene. To establish the long term efficacy and safety of toremifene for Japanese patients, we conducted a prospective, multicenter, randomized phase III trial comparing toremifene and tamoxifen.

PATIENTS AND METHODS

The subjects were postmenopausal Japanese patients who had undergone surgery for node-negative breast cancer. Toremifene or tamoxifen was administered for 2 years. The primary endpoint was demonstration of the non-inferiority of toremifene compared with tamoxifen in respect of 5-year survival. Secondary endpoints were cumulative overall survival, cumulative disease-free survival, effects on lipid profiles, and adverse events.

RESULTS

A total of 253 patients were enrolled. The baseline characteristics of the two treatment groups were well-balanced. Median follow-up was 66.5 months. Five-year survival was similar for toremifene and tamoxifen (97.0 vs. 96.9 %; 90 % confidence interval -3.9 to 4.1), indicating that toremifene is not inferior to tamoxifen for postmenopausal Japanese patients with early breast cancer. Cumulative overall survival and cumulative disease-free survival were also very similar for toremifene and tamoxifen (97.5 vs. 97.3 %, log-rank test P = 0.9458; 88.4 vs. 90.6 %, log-rank test P = 0.3359, respectively). Adverse events in both groups were similar and mostly mild or moderate. Thus, both are equally effective and well tolerated.

CONCLUSION

Our results suggest that the efficacy and safety of toremifene and tamoxifen are equivalent for postmenopausal Japanese patients with early breast cancer.

Systematic review of lapatinib in combination with letrozole compared with other first-line treatments for hormone receptor positive(HR+) and HER2+ advanced or metastatic breast cancer(MBC)

BACKGROUND

Third-generation aromatase inhibitors (letrozole, anastrozole) have shown superior efficacy in early and advanced breast cancer compared with tamoxifen. For HR+, HER2+ MBC, combination of an AI with an anti-HER2 agent (lapatinib or trastuzumab) has shown clinical benefit.

METHODS

Six databases were searched until January 2009 for randomized controlled clinical trials, assessing the safety and efficacy of first-line treatments for postmenopausal women with HR+ and HER2 (ErbB2) positive MBC, who have not received prior therapy for advanced or metastatic disease. Relevant interventions were lapatinib, aromatase inhibitors, tamoxifen, and trastuzumab. Outcomes included overall survival (OS), progression-free-survival (PFS), time-to-progression (TTP), and objective response rate (ORR).

RESULTS

Eighteen studies (62 papers) were included. Lapatinib + letrozole was significantly superior to letrozole alone based on a direct head-to-head study in terms of PFS/TTP and ORR. Using a network meta-analysis, compared with lapatinib + letrozole, tamoxifen (HR = 0.45 (95% CI: 0.32, 0.65) and anastrozole (HR = 0.53 (0.36, 0.80)) scored significantly worse in terms of PFS/TTP and ORR (tamoxifen: OR = 0.25 (0.12, 0.53), anastrozole: OR = 0.27 (0.12, 0.58). The combination also seemed significantly superior to exemestane in terms of PFS/TTP (HR = 0.52 (0.34, 0.79)). Lapatinib + letrozole also seemed better, although not significantly, in terms of OS versus tamoxifen: HR = 0.74 (0.49, 1.12), anastrozole: HR = 0.71 (0.45, 1.14) and exemestane: HR = 0.65 (0.39, 1.11). When compared with trastuzumab + anastrozole, lapatinib + letrozole seemed to be better in terms of OS (HR = 0.85 (0.47, 1.54)), PFS/TTP (HR = 0.89 (0.54, 1.47)) and ORR (OR = 0.92 (0.24, 3.48)), although, none of these results were significant.

DISCUSSION

Lapatinib + letrozole was significantly superior to letrozole in terms of PFS/TTP and ORR based on a direct head-to-head study. Indirect comparisons appeared to favor lapatinib + letrozole versus other first-line treatments used in this patient population in terms of three main outcomes: OS, PFS/TTP and ORR. Indirect comparison results are based on a network analysis for which the basic assumptions of homogeneity, similarity and consistency were not fulfilled. Therefore, despite the fact that these are the best available data, the results need to be interpreted with caution.

Toremifene versus tamoxifen for advanced breast cancer

BACKGROUND

Toremifene (TOR) and tamoxifen (TAM) can both be used as treatments for advanced breast cancer.

OBJECTIVES

To compare the efficacy and safety of TOR with TAM in patients with advanced breast cancer.

SEARCH METHODS

The Cochrane Breast Cancer Group's Specialised Register was searched (1 July 2011) using the codes for "toremifene", "fareston", "tamoxifen, "nolvadex, and "breast cancer". We also searched MEDLINE (via PubMed) (from inception to 1 July 2011), EMBASE (via Ovid) (from inception to 1 July 2011), The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 7, 2011), and the WHO International Clinical Trials Registry Platform search portal (1 July 2011). In addition, we screened the reference lists of relevant trials or reviews.

SELECTION CRITERIA

Randomised controlled trials (RCTs) that compared the efficacy and safety, or both of TOR with TAM in women with advanced breast cancer. Trials that provided sufficient data on one of the following items: objective response rate (ORR), time to progression (TTP), overall survival (OS), and adverse events, were considered eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Studies were assessed for eligibility and quality. Two review authors independently extracted the following details: first author, publication year, country, years of follow-up, treatment arms, intention-to-treat (ITT) population size, menopausal status of patients, hormone receptor status, response criteria, efficacy and safety outcomes of TOR and TAM arms. Hazard ratios (HR) were derived for time-to-event outcomes, where possible, and response and adverse events were analysed as dichotomous variables. We used a fixed-effect model for meta-analysis unless there was significant between-study heterogeneity.

MAIN RESULTS

A total of 2061 patients from seven RCTs were included for final analysis, with 1226 patients in the TOR group and 835 patients in the TAM group. The ORR for the TOR group was 25.8% (316/1226) whereas, the ORR for the TAM group was 26.9% (225/835). The pooled risk ratio (RR) suggested that the ORRs were not statistically different between the two groups (RR 1.02, 95% confidence interval (CI) 0.88 to 1.18, P = 0.83). The median TTP was 6.1 months for the TOR group and 5.8 months for the TAM group. The median OS was 27.8 months for the TOR group and 27.6 months for the TAM group. There were no significant differences in TTP and OS between the two therapeutic groups (for TTP: HR 1.08, 95% CI 0.94 to 1.24; for OS: HR 1.02, 95% CI 0.86 to 1.20). The frequencies of most adverse events were also similar in the two groups, while headache seemed to occur less in the TOR group than in the TAM group (RR 0.14, 95% CI 0.03 to 0.74, P = 0.02). There was no significant heterogeneity between studies in most of the above meta-analyses. Sensitivity analysis did not alter the results.

AUTHORS' CONCLUSIONS

TOR and TAM are equally effective and the safety profile of the former is at least not worse than the latter in the first-line treatment of patients with advanced breast cancer. Thus, TOR may serve as a reasonable alternative to TAM when anti-oestrogens are applicable but TAM is not the preferred choice for some reason.

A comparison of survival outcomes and side effects of toremifene or tamoxifen therapy in premenopausal estrogen and progesterone receptor positive breast cancer patients: a retrospective cohort study

BACKGROUND

In premenopausal women, endocrine adjuvant therapy for breast cancer primarily consists of tamoxifen alone or with ovarian suppressive strategies. Toremifene is a chlorinated derivative of tamoxifen, but with a superior risk-benefit profile. In this retrospective study, we sought to establish the role of toremifene as an endocrine therapy for premenopausal patients with estrogen and/or progesterone receptor positive breast cancer besides tamoxifen.

METHODS

Patients with early invasive breast cancer were selected from the breast tumor registries at the Sun Yat-Sen Memorial Hospital (China). Premenopausal patients with endocrine responsive breast cancer who underwent standard therapy and adjuvant therapy with toremifene or tamoxifen were considered eligible. Patients with breast sarcoma, carcinosarcoma, concurrent contralateral primary breast cancer, or with distant metastases at diagnosis, or those who had not undergone surgery and endocrine therapy were ineligible. Overall survival and recurrence-free survival were the primary outcomes measured. Toxicity data was also collected and compared between the two groups.

RESULTS

Of the 810 patients reviewed, 452 patients were analyzed in the study: 240 received tamoxifen and 212 received toremifene. The median and mean follow up times were 50.8 and 57.3 months, respectively. Toremifene and tamoxifen yielded similar overall survival values, with 5-year overall survival rates of 100% and 98.4%, respectively (p = 0.087). However, recurrence-free survival was significantly better in the toremifene group than in the tamoxifen group (p = 0.022). Multivariate analysis showed that recurrence-free survival improved independently with toremifene (HR = 0.385, 95% CI = 0.154-0.961; p = 0.041). Toxicity was similar in the two treatment groups with no women experiencing severe complications, other than hot flashes, which was more frequent in the toremifene patients (p = 0.049). No patients developed endometrial cancer.

CONCLUSION

Toremifene may be a valid and safe alternative to tamoxifen in premenopausal women with endocrine-responsive breast cancer.

Hormonal modulation in the treatment of breast cancer

This article explores the history of endocrine therapy for the treatment of breast cancer, the clinical evidence behind the current standards of care, and controversies that may change these standards in the future.

Excellent outcomes with adjuvant toremifene or tamoxifen in early stage breast cancer

BACKGROUND

Fareston (toremifene) and tamoxifen, both selective estrogen receptor modulators, are therapeutically equivalent treatments for metastatic breast cancer. We hypothesized that toremifene as compared with tamoxifen given as adjuvant therapy for early stage breast cancer would result in equivalent survival with an improved side effect profile, therefore, providing superior therapeutic efficacy.

METHODS

The North American Fareston versus Tamoxifen Adjuvant trial assigned 1813 perimenopausal or postmenopausal women with hormone receptor (HR)-positive invasive breast cancer to adjuvant treatment with either tamoxifen or toremifene. The primary outcomes evaluated were disease-free survival (DFS) and overall survival (OS).

RESULTS

Median follow-up was 59 months. The baseline characteristics of the 2 treatment groups were well-balanced. On the basis of intent-to-treat, 5-year actuarial DFS was not significantly different between tamoxifen and toremifene (91.2% [standard error of the mean [SE] 1.2%] vs 91.2% [SE 1.1%], respectively). Similarly, 5-year actuarial OS was not significantly different between tamoxifen and toremifene (92.7% [SE 1.1%] vs 93.7% [SE 1.0%], respectively). Controlling for patient age, tumor size, and tumor grade, a Cox multivariate survival analysis found no difference between patients randomized to toremifene versus tamoxifen in terms of OS (OR = 0.951; 95% confidence interval [CI], 0.623-1.451, P = .951) or DFS (OR = 1.037; 95% CI, 0.721-1.491, P = .846). Adverse events were similar in the 2 groups.

CONCLUSIONS

Women treated with adjuvant hormonal therapy enjoyed excellent DFS and OS. No significant differences were found between treatment with either tamoxifen or toremifene. Treatment of HR-positive patients with either tamoxifen or toremifene is appropriate.

Emerging drugs in metastatic breast cancer

BACKGROUND

Breast cancer is the most common cancer among women and comprises 26% of all cancers diagnosed in women in the United States. Among presenting patients, 3 - 6% already have metastatic disease, and 50 - 70% of the remaining patients develop systemic relapse. Recently many new drugs, particularly molecular targeted therapies, have been developed in the field.

OBJECTIVE

To review the current and emerging data on the treatment of metastatic breast cancer, with emphasis on novel therapies that show promise.

METHODS

PubMed and ASCO annual meeting abstracts were used for a literature search.

RESULTS/CONCLUSIONS

Despite improved response rates, conventional treatments still result only in transient remission in most cases. New therapeutic alternatives and new strategies to overcome drug resistance are needed to improve these results.

Comparing the effects of atamestane, toremifene and tamoxifen alone and in combination, on bone, serum lipids and uterus in ovariectomized rats

Complete estrogen blockade remains under investigation as a means to optimize anti-estrogen therapy in breast cancer thus both the efficacy and end-organ toxicities are of interest with combinations. We hypothesized that a steroidal aromatase inhibitor (AI) atamestane (ATA) alone, and in combination with the anti-estrogens tamoxifen (TAM) or toremifene (TOR) would have beneficial effects in ovariectomized (OVX) rats on key end-organ functions including bone and lipid metabolism and on the endometrium. Significant positive effects on bone were noted with ATA, TOR, TAM, ATA+TOR, or ATA+TAM. TOR, TAM, ATA+TOR, or ATA+TAM caused significant decreases in serum cholesterol and low-density lipoprotein cholesterol whereas ATA had no effect. Uterine weight and epithelium lining height were not increased by ATA but were by TOR and TAM. No significant differences were found in the key parameters outlined above between OVX rats given TOR and ATA+TOR, or TAM and ATA+TAM. Our data show that ATA in combination with TOR or TAM is equivalent to TOR or TAM alone in terms of end-organ effects within a range of clinically relevant doses. Further studies of combinations of AIs with anti-estrogens on end-organ function are merited.

Second non-breast primary cancer following adjuvant therapy for early breast cancer: a report from the International Breast Cancer Study Group

The incidence of second non-breast primary cancer following adjuvant treatment was evaluated using data from patients enrolled from 1978 to 1999 in four International Breast Cancer Study Group (IBCSG) trials. The occurrence of these tumours as sites of the first failure was assessed separately for two treatment comparisons: toremifene versus tamoxifen for 5 years in 1035 patients in IBCSG Trials 12-93 and 14-93 with a median follow-up of 8 years and endocrine therapy (toremifene or tamoxifen) versus chemo-endocrine therapy (CMF or AC plus toremifene or tamoxifen) in 1731 patients from IBCSG Trials III, VII and 12-93, with a combined median follow-up of 14 years. No significant differences in second non-breast primary tumours were observed in either comparison. In particular, the incidences of second primary uterine tumours with toremifene and tamoxifen were similar and no significant increase of secondary leukaemias was observed with chemo-endocrine therapy compared with endocrine therapy.

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.

The effects of atamestane and toremifene alone and in combination compared with letrozole on bone, serum lipids and the uterus in an ovariectomized rat model

We compared the effects of atamestane (ATA) and toremifene (TOR) alone and in combination, with letrozole (LET) on bone, serum lipids and the uterus in ovariectomized (OVX) rats after 16 weeks of treatment. Compared to OVX controls lumbar vertebral and femoral BMD as well as mechanical strength and trabecular bone volume were significantly greater in animals given ATA, TOR or ATA + TOR. The effects of ATA were not reversed by the androgen receptor blocker, flutamide (FLT). Serum cholesterol, low-density lipoprotein cholesterol and triglycerides were reduced by TOR and ATA + TOR whereas they remained unchanged in animals receiving ATA, ATA + FLT, and LET. The uterine epithelium in OVX animals was equally stimulated by TOR and ATA + TOR and unaffected by ATA or LET. Intact animals had significant atrophy of the uterine epithelium when receiving ATA. In summary, TOR alone or in combination with ATA had a predictable stimulatory effect on bone and the uterine epithelium while reducing key parameters of lipid metabolism. In contrast, ATA but not LET had an unexpected stimulatory effect on the OVX rat's bone and this was not reversed by the anti-androgen FLT leaving this finding unexplained for now. ATA is distinct from LET on end-organ function and this favorable profile makes clinical testing of this steroidal aromatase inhibitor of interest in the clinical setting.

Bone mineral density and lipid changes during 5 years of follow-up in a study of prevention of breast cancer with toremifene in healthy, high-risk pre- and post-menopausal women

A double-blind, randomised, placebo-controlled pilot study was initiated to evaluate the feasibility of chemoprevention with toremifene 60 mg/day in healthy women at high risk for breast cancer. Enrolment in the study was terminated earlier than planned because of slow patient accrual, although 13% of patients continued for 5 years. The revised efficacy outcomes were change in bone mineral density (BMD) from baseline at four skeletal sites, plus effects on serum lipids. In premenopausal women there was a trend for sustained increase in BMD during toremifene therapy after year 1 in lumbar spine. In postmenopausal women, toremifene had little or no effect on BMD trends. Levels of total and low-density lipoprotein (LDL) cholesterol were largely unchanged from baseline in premenopausal women treated with toremifene but were often slightly lower than in the placebo group during follow-up. Total and LDL cholesterol levels declined slightly from baseline in the postmenopausal women and were, at several points during the first 3 years, significantly lower than in the corresponding placebo group (p < 0.01). We conclude that: (a) assessment of toremifene 60 mg/day in chemoprevention will require further clinical trials; (b) toremifene 60 mg/day has no substantive negative effects on BMD in pre- or postmenopausal women and may exert a minor favourable influence (in particular, the effects of toremifene 60 mg/day on BMD in premenopausal women may make the drug an attractive alternative to tamoxifen 20 mg/day for that patient subset); (c) lipid effects of toremifene 60 mg/day are, at minimum, neutral and may be modestly favourable for reducing cardiovascular risk.

Endocrine therapy--current benefits and limitations

Endocrine therapy is a valuable option for the treatment of postmenopausal women with estrogen receptor (ER)-positive breast cancer due to its demonstrated efficacy and favorable safety profile. Although tamoxifen has been the established treatment for more than 20 years its long-term use is associated with several tolerability concerns and may lead to increased risk of endometrial cancer and thromboembolic complications. In addition, many patients who initially respond to treatment with endocrine agents such as tamoxifen eventually relapse with resistant disease. Sequential use of endocrine therapies is often used in patients as resistance to individual agents develops. Several endocrine approaches have been developed that deprive the tumor of estrogen stimulation, either by directly modulating the ER-signaling pathway or by lowering serum or tumor concentrations of estrogen. In the classic pathway of estrogen signal transduction, the steroid hormone binds to its intracellular ER, triggering a cascade of events that ultimately leads to altered gene transcription. More recently, it has become apparent that ER activation can also occur via estrogen-independent receptor activation or by non-nuclear action through cell surface receptors. Consequently, molecular cross-talk exists between the ER and growth factor signaling cascades, which is a key factor in de novo and acquired resistance to endocrine therapy. Inappropriate activation of growth factor signaling can readily promote endocrine therapy failure in breast cancer cells, either by overriding the growth-inhibitory properties of antiestrogenic drugs or by establishment of a new self-propagating autocrine loop that efficiently drives resistant cell growth. Fulvestrant is a new type of ER antagonist with no agonist effects that binds, blocks and causes degradation of the ER. As multiple signaling pathways are involved in the activation of ER, the use of agents such as fulvestrant that directly target the ER and lead to both degradation of the receptor and abrogation of ER signaling may prevent or delay the development of absolute endocrine resistance. In addition, combining antiestrogenic drugs with inhibitors of cell signaling molecules to target both the ER and growth factor signaling pathways is likely to provide a means of delaying endocrine therapy resistance, leading the way to more effective breast cancer treatment.

Toremifene: an evaluation of its safety profile

Toremifene has been in clinical use for 8 years for the treatment of advanced hormone-sensitive breast cancer and the adjuvant treatment of early breast cancer. More than 350,000 patient treatment years have accumulated, sufficient to allow evaluation of its longer-term safety profile in comparison with tamoxifen and, where possible, with raloxifene and aromatase inhibitors. We reviewed all preclinical and clinical safety data from 1978 to 2004 and comparative clinical safety data between October 1995 and the end of 2004. Secondary endometrial cancer incidence was lower with toremifene than with tamoxifen and was similar to that with raloxifene. It is speculated that toremifene may unmask existing endometrial tumors rather than induce new events. The risk of stroke, pulmonary embolism, and cataract may be lower with toremifene than with tamoxifen and the risk of pulmonary embolism and deep vein thrombosis lower than with raloxifene. Beneficial estrogen agonistic effects were equivalent to those of tamoxifen regarding bone mineral density and superior regarding lipid profiles.

Treating urogenital atrophy

Urogenital atrophy, although a frequently occurring symptom of aging for all women, is a condition often not thought of as a symptom of distress for older women or a sign of pelvic pathology requiring treatment by clinicians. Rather, many clinicians feel it is an expected consequence of aging, and older women themselves assimilate their lifestyle to the uncomfortable symptoms of dryness, irritation, itching and malodorous discharge. At times, when symptoms become intolerable with coitus, women will abandon sexual intercourse with their partners due to dyspareunia and not seek intervention to reverse the condition owing to embarrassment in raising this sensitive topic. When urogenital atrophy is diagnosed and the patient requests treatment, the gold standard intervention is estrogen, which can either be delivered systemically or vaginally. Since the Women's Health Initiative data, low-dose, vaginally delivered estrogen is recommended.

Toremifene and tamoxifen are equally effective for early-stage breast cancer: first results of International Breast Cancer Study Group Trials 12-93 and 14-93

BACKGROUND

Toremifene is a chlorinated derivative of tamoxifen, developed to improve its risk-benefit profile. The International Breast Cancer Study Group (IBCSG) conducted two complementary randomized trials for peri- and postmenopausal patients with node-positive breast cancer to compare toremifene versus tamoxifen as the endocrine agent and simultaneously investigate a chemotherapy-oriented question. This is the first report of the endocrine comparison after a median follow-up of 5.5 years.

PATIENTS AND METHODS

1035 patients were available for analysis: 75% had estrogen receptor (ER)-positive primary tumors, the median number of involved axillary lymph nodes was three and 81% received prior adjuvant chemotherapy.

RESULTS

Toremifene and tamoxifen yielded similar disease-free (DFS) and overall survival (OS): 5-year DFS rates of 72% and 69%, respectively [risk ratio (RR)=0.95; 95% confidence interval (CI)=0.76-1.18]; 5-year OS rates of 85% and 81%, respectively (RR = 1.03; 95% CI = 0.78-1.36). Similar outcomes were observed in the ER-positive cohort. Toxicities were similar in the two treatment groups with very few women (<1%) experiencing severe thromboembolic or cerebrovascular complications. Quality of life results were also similar. Nine patients developed early stage endometrial cancer (toremifene, six; tamoxifen, three).

CONCLUSIONS

Toremifene is a valid and safe alternative to tamoxifen in postmenopausal women with endocrine-responsive breast cancer.

Endocrinology and hormone therapy in breast cancer: selective oestrogen receptor modulators and downregulators for breast cancer - have they lost their way?

Although tamoxifen has been an effective treatment for breast cancer, several novel anti-oestrogen compounds have been developed with a reduced agonist profile on breast and gynaecological tissues. These include selective oestrogen receptor modulators (SERMs; both 'tamoxifen-like' and 'fixed-ring' SERMs) and selective oestrogen receptor downregulators (SERDs), although none has been proved superior in efficacy to tamoxifen in various advanced breast cancer trials. Thus, many have questioned whether a need for SERMs in breast cancer still exists, although chemoprevention remains a possible niche setting. In contrast, SERDs may have useful efficacy following aromatase inhibitors because of their unique mechanism of action, and clinical trials to determine their optimal use or sequence are ongoing.

Selective oestrogen receptor modulators/new antioestrogens: a clinical perspective

Following tamoxifen, the first selective oestrogen receptor modulator (SERM), a number of other antioestrogens have been developed. The first-generation SERMs exhibit cross-resistance with tamoxifen and have agonist effects on the uterus. Toremifene has equal efficacy to tamoxifen and may be useful as a tamoxifen alternative. Efficacy results for droloxifene and idoxifene were disappointing and their clinical development ceased. Response rates for second-generation SERMs such as raloxifene and arzoxifene are also not high, although raloxifene shows promise in the chemoprevention of breast cancer. Paradoxically, high-dose oestrogens are proving to be effective breast cancer treatment with similar responses to tamoxifen in postmenopausal women with advanced disease, although these drugs are not well tolerated. Fulvestrant is a new type of oestrogen receptor (ER) antagonist with no agonist effects, which binds, blocks and degrades the ER. Fulvestrant produces high response rates compared with the SERMs, is not cross-resistant with SERMs or aromatase inhibitors (AIs) and is equally as effective as the AI anastrozole in the treatment of postmenopausal women with advanced breast cancer who have progressed after prior antioestrogen therapy. Pure antioestrogens such as the ER antagonist fulvestrant provide opportunities for therapeutic sequencing with tamoxifen and AIs and offer exciting possibilities for the future treatment of breast cancer.

The use of selective estrogen receptor modulators and selective estrogen receptor down-regulators in breast cancer

Tamoxifen is one of the most effective treatments for breast cancer through its ability to antagonize estrogen-dependent growth by binding estrogen receptors (ERs) and inhibiting proliferation of breast epithelial cells. However, tamoxifen has estrogenic agonist effects in other tissues such as bone and endometrium due to liganded ER activating target genes in these different types of cell. Several novel anti-estrogen compounds have been developed which have a reduced agonist profile on breast and gynaecological tissues. These compounds offer the potential for enhanced efficacy and reduced toxicity compared with tamoxifen. In advanced breast cancer clinical data exist for two groups of agents: the selective estrogen receptor modulators (SERMs), further divided into "tamoxifen-like" (e.g. toremifene, droloxifene and idoxifene) and "fixed ring" compounds (e.g. raloxifene, arzoxifene and EM-800), and the selective estrogen receptor down-regulators (SERDs; e.g. fulvestrant (ICI 182780), SR 16234 and ZK 191703) also termed "pure anti-estrogens". In phase II trials in tamoxifen-resistant metastatic breast cancer the SERMs show low objective response rates (range 0-15%), suggesting cross resistance with tamoxifen. Randomized phase III trials for toremifene and idoxifene in over 1500 patients showed no significant difference compared with tamoxifen. Fewer clinical data exist for the "fixed ring" SERMs and it remains unclear whether any clinical advantage exists for the "fixed ring" SERMs over tamoxifen as first-line therapy. The main advantage for SERMs such as tamoxifen and raloxifene probably remains in early-stage disease (adjuvant therapy or prevention). Fulvestrant and the other SERDs have a high affinity for the estrogen receptor (ER) compared to tamoxifen, but none of its agonist activities. Of the SERDs, only fulvestrant has entered the clinic and this new agent is showing promising clinical activity in the treatment of advanced breast cancer. Recently published phase III studies have shown fulvestrant to be at least as effective as the third-generation aromatase inhibitor anastrozole in patients whose disease has relapsed or progressed on prior endocrine therapy. Surprisingly, however, in a phase III trial versus tamoxifen for the first-line therapy of advanced breast cancer fulvestrant did not attain the requirements for equivalence to tamoxifen, and in terms of time-to-treatment failure was inferior (5.9 versus 7.8 months for fulvestrant and tamoxifen, respectively; P=0.029). Future clinical studies will evaluate fulvestrant in the neoadjuvant setting together with its optimal sequencing in relation to tamoxifen and other endocrine therapies in advanced disease.

Effects of ospemifene, a novel SERM, on hormones, genital tract, climacteric symptoms, and quality of life in postmenopausal women: a double-blind, randomized trial

OBJECTIVE

Ospemifene, a novel selective estrogen receptor modulator, shows a potential for prevention and treatment of osteoporosis in postmenopausal women. We studied the effects of ospemifene on hormone levels, genital tract organs, climacteric symptoms, and quality of life.

DESIGN

A double-blinded study in which 160 postmenopausal women were randomly allocated to receive either ospemifene at three different daily doses (30, 60, or 90 mg) or placebo for 3 months.

RESULTS

No significant differences were observed among the study groups in clinical characteristics or parameters reflecting estrogen action at baseline. Ospemifene reduced follicle-stimulating hormone and insulin-like growth factor I levels, whereas estradiol failed to change at all, and luteinizing hormone was reduced only in the 90-mg group of ospemifene. In the vast majority of participants, the endometrium remained atrophic after 3 months of treatment with ospemifene. Although the rate of proliferative endometrium slightly increased in all groups, including placebo, no hyperplasia or bleeding occurred in any participant. Ospemifene had no effect on the appearance of proliferation marker Ki-67 in the endometrium as compared with placebo, and endometrial thickness increased by mean 0.4 to 0.6 mm (P < 0.01, P < 0.05 and P < 0.05 for 30, 60 and 90 mg ospemifene, respectively). Uterine volume slightly increased (8.4%-14.7%) in the ospemifene groups (P > 0.05), perhaps as a result of increased uterine blood flow. The most conspicuous finding was the significant estrogenic effect on vaginal epithelium, as evidenced by an increase in intermediate and superficial cells in repeat Pap smears. Ospemifene was not observed to aggravate climacteric symptoms or cause adverse events, nor did it suppress climacteric symptoms.

CONCLUSIONS

Ospemifene at daily doses of 30 to 90 mg did not stimulate endometrium or aggravate hot flashes but clearly had a rather strong estrogenic effect on the vaginal epithelium during a 3-month treatment period. Such effects would be advantageous if ospemifene were found to be effective in the long-term prevention of osteoporosis.

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

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

Effects of low dose tamoxifen on normal breast tissue from premenopausal women

The aim of this study was to determine the effects of low doses of tamoxifen (5 and 10mg/day) for 50 days compared with the standard dose (20 mg/day) on breast biomarkers measured in normal breast tissue from premenopausal patients. A randomised double-blind study was performed using tissue from 56 premenopausal women with a diagnosis of fibroadenoma of the breast. Excisional biopsy was performed on the 50th day of therapy. Normal breast tissue samples were collected during surgery. The patients were divided in groups: A (placebo, n=11); group B (5 mg, n=16), group C (10 mg, n=14) and group D (20 mg, n=15). In this cross-sectional study, differences in the expression of Oestrogen Receptor alpha (ERalpha), Progesterone Receptor (PR), Ki-67, apoptotic bodies and mitotic index between the different groups after treatment can be seen on the normal breast tissue. We believe that a lower dose of tamoxifen could reduce the side-effects associated with treatment without affecting its chemopreventive activity in the breast.

Neurologic complications of cancer therapy

Neurologic complications of chemotherapy are relatively common. The diagnosis of chemotherapy-associated neurotoxicity remains a clinical one, and is largely based on the exclusion of other possible causes. The goal of this review is to describe the neurotoxicity associated with established chemothrerapeutic agents and with some of the newer biologic agents, monoclonal antibodies and targeted molecular therapies used in the treatment of cancer.

Antiaromatase agents: evolving role in adjuvant therapy

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

Role of antiestrogens and aromatase inhibitors in breast cancer treatment

This review explores the recent experience with, and the basis for, the use of selective estrogen receptor modulators to treat and prevent breast cancer. As new agents are unveiled, they will continue to be tested against tamoxifen. A number of new selective estrogen receptor modulators are in clinical development in an attempt to decrease the unwanted effects of tamoxifen. Raloxifene holds the promise of treating osteoporosis with the beneficial side effect of breast cancer prevention. Additionally, two different classes of hormonal agents, the aromatase inhibitors and estrogen receptor down-regulators, which have no estrogen-like properties at any site, appear to be promising new treatments for advanced breast cancer.