Intent-to-treat analysis of the placebo-controlled trial of letrozole for extended adjuvant therapy in early breast cancer: NCIC CTG MA.17

10 years or less of extended adjuvant endocrine therapy for postmenopausal breast cancer patients: A systematic review and network meta-analysis

INTRODUCTION

Adjuvant hormonal therapy, with or without prior chemotherapy, has been widely recognised as the preferred treatment strategy for resected breast cancer (BC) for a minimum duration of 5 years. If the effectiveness of therapy beyond a 5-year period has been established, there is still ongoing debate regarding the optimal duration for this prolonged period. A network meta-analysis (NMA) was conducted to ascertain the optimal duration of extended therapy for resected BC in postmenopausal women.

MATERIAL AND METHODS

A comprehensive search was conducted on online databases, including MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials, to identify all randomised trials on extended duration of endocrine therapy. The search was limited to trials that had been published before 30th April 2023. The study focused on evaluating disease-free survival (DFS) as the primary outcome, with overall survival (OS) as the secondary endpoint. Under the Bayesian framework, NMA was performed using the GeMTC package. The relative rankings of the treatments were determined by utilising surface under the cumulative ranking curve (SUCRA) p scores. A network meta-regression analysis was employed to ascertain the impact of the baseline characteristics of the disease and the initial treatments administered.

RESULTS

In the overall population, increasing the duration by 5 years did not result in a significantly better DFS compared to durations of 2-3 and 3-4 more years (hazard ratio [HR] = 0.97, 95% confidence interval [CI] [0.88-1.08] and HR = 0.87, 95% CI [0.72-1.06]). This effect was independent of adjuvant chemotherapy and nodal status. However, the effect of 5 more years of AI was significantly better in node-positive BC and in those who received some years of tamoxifen instead of aromatase inhibitors (AIs) as initial adjuvant therapy. OS was not affected by the administration of extended endocrine therapy.

CONCLUSIONS

We conclude that an extended course of AI lasting 2-3 years, following an initial 5-year treatment, may be considered an appropriate regimen for achieving DFS benefits. In node-positive BC cases, it has been observed that a duration of 10 years provides a greater advantage compared to shorter durations, especially when tamoxifen is administered initially. Therefore, it is suggested that a longer duration is a potential standard of care in these cases.

Extended adjuvant endocrine therapy for women with hormone receptor-positive early breast cancer: A meta-analysis with trial sequential analysis of randomized controlled trials

OBJECTIVES

The aim of the current study is to explore the association between extended adjuvant endocrine treatment and prognosis of women with hormone receptor-positive (HR+) early breast cancer.

METHODS

Databases including PubMed, Web of Science, Embase and the Cochrane Library databases were electronically searched to identify randomized controlled trials (RCTs) that reported extended endocrine therapy for women with HR+ early breast cancer. The retrieval time was limited from inception to September 2022. Two reviewers independently screened literature, extracted data, and assessed risk bias of included studies. Meta-analysis was performed by using R software Version 4.1.2 and STATA Version 12.0.

RESULTS

A total of 15 RCTs involving 29497 cases were included. The overall analysis showed that compared with the control, extended adjuvant endocrine therapy increased disease-free survival (DFS) (HR=0.814, 95% CI: 0.720-0.922, 95% PI: 0.556-1.194), overall survival (OS) (HR=0.885, 95% CI: 0.822-0.953, 95% PI: 0.771-1.035), relapse-free survival (RFS) (HR=0.833, 95% CI: 0.747-0.927, 95% PI: 0.575-1.159), distant metastatic-free survival (DMFS) (HR=0.824, 95% CI: 0.694-0.979, 95% PI: 0.300-2.089) and reduced new breast cancer cumulative incidence (NBCCI) (HR=0.484, 95% CI: 0.403-0.583, 95% PI: 0.359-0.654). For adverse events, extended adjuvant endocrine treatment was associated with a significantly higher risk of bone fracture (RR=1.446, 95% CI: 1.208-1.730, 95% PI: 1.154-1.854) and osteoporosis (RR=1.377, 95% CI: 1.018-1.862, 95% PI: 0.347-5.456).

CONCLUSION

Our study showed that extended adjuvant endocrine therapy increased DFS, OS, RFS, DMFS, the incidence of bone fracture and osteoporosis, and reduced NBCCI.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero, identifier (CRD42022351295).

Landmark trials in the medical oncology management of early stage breast cancer

With the advent of breast cancer screening programs, the majorities of patients with newly diagnosed breast cancer are diagnosed with early stage disease and are likely to experience cure with proper treatment. Significant advances have been made in the management of early-stage breast cancer to personalize treatment according to disease biology. This progress has led to improvement in survival outcomes and quality of life for our patients. In this review, we discuss landmark clinical trials in medical oncology that have shaped the current standard of care for early stage ER-positive, HER2-positive, and triple negative breast cancer.

A population-based analysis of breast cancer incidence and survival by subtype in Ontario women

Background

Breast cancer (bca) is the type of cancer most frequently diagnosed among women in Canada. Breast cancer is categorized into various molecular subtypes by the expression of estrogen receptor (er), progesterone receptor (pgr), and her2 (human epidermal growth factor receptor 2). Currently, Canada has no national cancer registry with epidemiology data by subtype. Thus, we conducted a study to determine incidence, survival, and clinicopathologic characteristics by bca subtype [triple negative breast cancer (tnbc); her2+; and hormone receptor-positive (hr+), her2-] in Canadian women newly diagnosed with bca.

Methods

Female patients diagnosed between 1 April 2012 and 31 March 2016 (fiscal 2012-2015) were identified in the Ontario Cancer Registry, and individual patient data were linked to data in provincial health administrative databases. Descriptive statistics and Kaplan-Meier curves were generated.

Results

In this cohort, 3277 women (9.5%) had tnbc, 4902 (14.3%) had her2+ bca, and 22,247 (64.8%) had hr+, her2-breast cancer. The annual incidence was 15 per 100,000 for the tnbc group, 21-23 per 100,000 for the her2+ group, and 97-105 per 100,000 for the hr+, her2- group. The lowest median overall survival (mos) of 8.9 months was observed in women with clinical stage iv tnbc. In comparison, the mos was 37.3 months in those with her2+ disease and 35.2 months in those with and hr+, her2- metastatic bca.

Conclusions

In the present study, the most recent and largest administrative database analysis of a Canadian population to date, we observed a subtype distribution consistent with previously reported data, together with comparable annual incidence and overall survival patterns.

Long-term survival outcomes of triple-receptor negative breast cancer survivors who are disease free at 5 years and relationship with low hormone receptor positivity

Background:

We counsel our triple-negative breast cancer (TNBC) patients that the risk of recurrence is highest in the first 5 years after diagnosis. However, there are limited data with extended follow-up on the frequency, characteristics, and predictors of late events.

Methods:

We queried the MD Anderson Breast Cancer Management System database to identify patients with stage I–III TNBC who were disease free at 5 years from diagnosis. The Kaplan–Meier method was used to estimate yearly recurrence-free interval (RFI), recurrence-free survival (RFS), and distant relapse-free survival (DRFS), as defined by the STEEP criteria. Cox proportional hazards model was used to compute hazard ratios (HRs) and 95% confidence intervals (CIs).

Results:

We identified 873 patients who were disease free at least 5 years from diagnosis with median follow-up of 8.3 years. The 10-year RFI was 97%, RFS 91%, and DRFS 92% the 15-year RFI was 95%, RFS 83%, and DRFS 84%. On a subset of patients with oestrogen receptor and progesterone receptor percentage recorded, low hormone receptor positivity conferred higher risk of late events on multivariable analysis for RFS only (RFI: HR=1.98, 95% CI=0.70–5.62, P-value=0.200; RFS: HR=1.94, 95% CI=1.05–3.56, P-value=0.034; DRFS: HR=1.72, 95% CI=0.92–3.24, P-value=0.091).

Conclusions:

The TNBC survivors who have been disease free for 5 years have a low probability of experiencing recurrence over the subsequent 10 years. Patients with low hormone receptor-positive cancers may have a higher risk of late events as measured by RFS but not by RFI or DRFS.

Optimal Duration of Extended Adjuvant Endocrine Therapy for Early Breast Cancer; Results of the IDEAL Trial (BOOG 2006-05)

Background

The optimal duration of extended endocrine therapy beyond five years after initial aromatase inhibitor-based adjuvant therapy for postmenopausal women with hormone receptor-positive breast cancer is still unknown. Therefore, we conducted a clinical trial to compare two different extended endocrine therapy durations.

Methods

In the randomized phase III IDEAL trial, postmenopausal patients with hormone receptor-positive breast cancer were randomly allocated to either 2.5 or five years of letrozole after the initial five years of any endocrine therapy. The primary end point was disease free survival (DFS), and secondary end points were overall survival (OS), distant metastasis-free interval (DMFi), new primary breast cancer, and safety. Hazard ratios (HRs) were determined using Cox regression analysis. All analyses were by intention-to-treat principle.

Results

A total of 1824 patients were assigned to either 2.5 years (n = 909) or five years (n = 915) of letrozole, with a median follow-up of 6.6 years. A DFS event occurred in 152 patients in the five-year group, compared with 163 patients in the 2.5-year group (HR = 0.92, 95% confidence interval [CI] = 0.74 to 1.16). OS (HR = 1.04, 95% CI = 0.78 to 1.38) and DMFi (HR = 1.06, 95% CI = 0.78 to 1.45) were not different between both groups. A reduction in occurrence of second primary breast cancer was observed with five years of treatment (HR = 0.39, 95% CI = 0.19 to 0.81). Subgroup analysis did not identify patients who benefit from five-year extended therapy.

Conclusion

This study showed no superiority of five years over 2.5 years of extended adjuvant letrozole after an initial five years of adjuvant endocrine therapy.

Breast Ductal Carcinoma In Situ: A Literature Review of Adjuvant Hormonal Therapy

This review paper analyzed publications of adjuvant tamoxifen and aromatase inhibitor use following surgery for breast ductal carcinoma in situ (DCIS). Key endpoint analyses were risk of invasive and noninvasive malignancies and new contralateral breast cancers. Metaanalysis of three studies showed a relative risk of 0.69 (95% confidence interval, 0.60-0.79, P<0.05) for breast malignancies with tamoxifen treatment in a mixed radiotherapy treatment/naïve cohort. Subgroup analysis of DCIS populations in multiple studies showed a trend to benefit with aromatase inhibitor treatment.

Male breast cancer is not congruent with the female disease

It has become customary to extrapolate from the results of treatment trials for female breastcancer and apply them to males with the disease. In the absence of results from national and international randomised trials for male breast cancer (MBC) this appears superficially to be an appropriate response. Closer examination of available data reveals that aspects of the aetiology and treatment of MBC do not fit the simplistic model that men usually have endocrine sensitive tumours which behave like those in postmenopausal women. Most females and males with breast cancer have none of the recognised risk factors, indicating the gaps in our knowledge of the epidemiology of this disease. Several studies have compared epidemiological risk factors for MBC and female breast cancer (FBC) but many have been blighted by small numbers. In comparison with FBC there is a larger proportion of BRCA2 tumours, (occurring in 10% of MBC), and underrepresentation of BRCA1 tumours (found in only 1%), suggesting significant differences in the genetic aetiology of MBC and FBC. Genome-wide association studies in FBC reported single nucleotide polymorphisms (SNPs) in 12 novel independent loci were consistently associated with disease but for MBC 2 SNPs had a significantly increased risk. Molecular profiles of matched cancers in males and females showed a gender-associated modulation of major processes including energy metabolism, regulation of translation, matrix remodelling and immune recruitment. Immunohistochemistry for kinase inhibitor proteins (KIPs) p27Kip1 and p21Waf1 indicate a significant difference in the immunostaining of tumours from male patients compared with females. MBC is almost always estrogen receptor positive (ER+ve) and so systemic treatment is usually endocrine. With evidence in FBC that aromatase inhibitors are more effective than tamoxifen in the postmenopausal it was seemingly logical that the same would be true for MBC. Results however suggest less efficacy with AIs and an increase in risk of mortality compared to tamoxifen. The overall survival in male breast cancer was significantly better after adjuvant treatment with tamoxifen compared to an aromatase inhibitor. These important biological differences point the way to the development of new therapies for MBC based on differences rather than similarities with FBC.

Aromatase inhibitors alone or sequentially combined with tamoxifen in postmenopausal early breast cancer compared with tamoxifen or placebo - Meta-analyses on efficacy and adverse events based on randomized clinical trials

Tamoxifen (TAM) and aromatase inhibitors (AI) are adjuvant therapy options for postmenopausal women with estrogen receptor positive (ER+) breast cancer. This systematic review of seven randomized controlled studies comparing TAM and AI, and one study comparing extended therapy with an AI with placebo after about 5 years of tamoxifen, aims to assess long-term clinical efficacy and adverse events. The literature review was performed according to the principles of the Cochrane Collaboration. The search included common databases up to 2013-01-14. Studies of high or moderate quality were used for grading of evidence. Revman™ software was utilized for meta-analyses of published data. Disease free survival (DFS) and overall survival (OS) were improved with AI monotherapy compared to TAM with high and moderate quality of evidence respectively. Sequenced therapy with AI → TAM (or vice versa) improved DFS compared with TAM with moderate quality of evidence, but did not improve OS (low quality of evidence). However, if only studies on sequenced AI therapy with randomization before endocrine therapy were considered, no improvement of DFS could be found. Fractures are more frequently associated with AI whereas the risk of endometrial cancer and venous thromboembolism are higher with TAM. For cardiovascular events no difference was found between AI (mono- or sequenced therapy) and TAM, whereas sequenced therapy compared with AI had lower risk of cardiovascular events (moderate level of evidence). AIs are superior to TAM as adjuvant hormonal therapy for postmenopausal ER-positive breast cancer. TAM can be considered for individual patients due to the different toxicity profile compared with AI. Cardiovascular events related to AI treatment deserve further attention.

St. Gallen/Vienna 2015: A Brief Summary of the Consensus Discussion

The 2015 St. Gallen Consensus Conference on early breast cancer took place in Vienna, Austria, for the first time. After 3 days of high-level presentations by international panel members of clinical trials having been reported recently in the field, the traditional Saturday voting tried to translate the assembled knowledge into clinical treatment recommendations intended to guide clinical practice of breast cancer care for the 'average' patient. This report summarizes the results of the 2015 international panel voting procedures with respect to locoregional and endocrine treatment, chemotherapy, targeted therapy, as well as adjuvant bisphosphonate use. This report is not aimed to replace the official St. Gallen consensus publication - some recommendations may even be altered in the final paper - but should serve as a preliminary rapid report of this important meeting.

Adjuvant endocrine therapy for early breast cancer: a systematic review of the evidence for the 2014 Cancer Care Ontario systemic therapy guideline

BACKGROUND

Cancer Care Ontario's Program in Evidence-Based Care (pebc) recently created an evidence-based consensus guideline on the systemic treatment of early breast cancer. The evidence for the guideline was compiled using a systematic review to answer the question "What is the optimal systemic therapy for patients with early-stage, operable breast cancer, when patient and disease factors are considered?" The question was addressed in three parts: cytotoxic chemotherapy, endocrine treatment, and her2 (human epidermal growth factor receptor 2)-targeted therapy.

METHODS

For the systematic review, the literature in the medline and embase databases was searched for the period January 2008 to May 2014. The Standards and Guidelines Evidence directory of cancer guidelines and the Web sites of major oncology guideline organizations were also searched. The basic search terms were "breast cancer" and "systemic therapy" (chemotherapy, endocrine therapy, targeted agents, ovarian suppression), and results were limited to randomized controlled trials (rcts), guidelines, systematic reviews, and meta-analyses.

RESULTS

Several hundred documents that met the inclusion criteria were retrieved. Meta-analyses from the Early Breast Cancer Trialists' Collaborative Group encompassed many of the rcts found. Several additional studies that met the inclusion criteria were retained, as were other guidelines and systematic reviews.

SUMMARY

The results of the systematic review constitute a comprehensive compilation of high-level evidence, which was the basis for the 2014 pebc guideline on systemic therapy for early breast cancer. The review of the evidence for systemic endocrine therapy (adjuvant tamoxifen, aromatase inhibitors, and ovarian ablation and suppression) is presented here; the evidence for chemotherapy and her2-targeted treatment-and the final clinical practice recommendations-are presented separately in this supplement.

Status of adjuvant endocrine therapy for breast cancer

Adjuvant endocrine therapy reduces the risk of recurrence and death from breast cancer in women with hormone receptor-positive early breast cancer. Tamoxifen has been the standard therapy for decades, and this is still the case for pre-menopausal women. Ovarian suppression is of similar efficacy but currently there is no strong evidence for adding this to tamoxifen and the additional morbidity can be considerable. Results from two important trials addressing this issue are imminent. In post-menopausal women, aromatase inhibitors (AIs) (letrozole, anastrozole, or exemestane) are superior to tamoxifen in preventing recurrence but only letrozole has been shown to improve survival. The main gain is against high-risk cancers, and tamoxifen gives very similar benefit for low-risk disease. Traditionally, treatment has been given for around 5 years, but many women remain at risk of relapse for 10 years or more. The AIs, and more recently tamoxifen, have been shown to reduce further the risk of late recurrence in women still in remission after 5 years of tamoxifen if given for a further 5 years. The comparative benefits of these two options and the selection of patients most likely to benefit from long-term adjuvant endocrine therapy are important topics for further research, as is the optimum duration of AI therapy started upfront.

Extended adjuvant endocrine therapy in hormone-receptor positive breast cancer

A high ongoing recurrence rate in patients with endocrine responsive breast cancer provides the rationale for offering endocrine treatment for more than five years. The MA.17 study, comparing the aromatase inhibitor (AI) letrozole for five years after an initial five years of tamoxifen to no further treatment, provided the proof-of-principle for extended endocrine treatment. These results have meanwhile been confirmed by several other studies and an EBCTCG meta-analysis. More recently, data from the ATLAS trial, comparing 10 to five years of tamoxifen, have been published, similarly showing a benefit for longer endocrine treatment with tamoxifen. In postmenopausal women -including those who had been premenopausal at initial diagnosis - a cross-trial comparison of ATLAS and the AI studies indicates superiority of switching to letrozole versus ongoing tamoxifen, similar to superiority of the AIs over tamoxifen in the metastatic and early breast cancer settings.

Adjuvant endocrine therapy for women with hormone receptor-positive breast cancer: american society of clinical oncology clinical practice guideline focused update

PURPOSE

To update the ASCO clinical practice guideline on adjuvant endocrine therapy on the basis of emerging data on the optimal duration of treatment, particularly adjuvant tamoxifen.

METHODS

ASCO convened the Update Committee and conducted a systematic review of randomized clinical trials from January 2009 to June 2013 and analyzed three historical trials. Guideline recommendations were based on the Update Committee's review of the evidence. Outcomes of interest included survival, disease recurrence, and adverse events.

RESULTS

This guideline update reflects emerging data on duration of tamoxifen treatment. There have been five studies of tamoxifen treatment beyond 5 years of therapy. The two largest studies with longest reported follow-up show a breast cancer survival advantage with 10-year durations of tamoxifen use. In addition to modest gains in survival, extended therapy with tamoxifen for 10 years compared with 5 years was associated with lower risks of breast cancer recurrence and contralateral breast cancer.

RECOMMENDATIONS

Previous ASCO guidelines recommended treatment of women who have hormone receptor-positive breast cancer and are premenopausal with 5 years of tamoxifen, and those who are postmenopausal a minimum of 5 years of adjuvant therapy with an aromatase inhibitor or tamoxifen followed by an aromatase inhibitor (in sequence). If women are pre- or perimenopausal and have received 5 years of adjuvant tamoxifen, they should be offered 10 years total duration of tamoxifen. If women are postmenopausal and have received 5 years of adjuvant tamoxifen, they should be offered the choice of continuing tamoxifen or switching to an aromatase inhibitor for 10 years total adjuvant endocrine therapy.

Scientific rationale for postmenopause delay in the use of conjugated equine estrogens among postmenopausal women that causes reduction in breast cancer incidence and mortality

High-dose synthetic estrogens were the first successful chemical therapy used in the treatment of metastatic breast cancer in postmenopausal women, and this approach became the standard of care in postmenopausal women with metastatic breast cancer between the 1950s and the end of the 1970s. The most recent analysis of the Women's Health Initiative estrogen-alone trial in hysterectomized women revealed a persistently significant decrease in the incidence of breast cancer and breast cancer mortality. Although estrogens are known to induce the proliferation of breast cancer cells, we have shown that physiologic concentrations induce apoptosis in breast cancer cells with long-term estrogen deprivation. We have developed laboratory models that illustrate the new biology of estrogen-induced apoptosis or growth to explain the effects of estrogen therapy. The key to the success of estrogen therapy lies in a sufficient period of withdrawal of physiologic estrogens (5-10 y) and the subsequent regrowth of nascent breast tumor cells that survive under estrogen-deprived conditions. These nascent tumors are now vulnerable to estrogen-induced apoptosis.

The optimal duration and selection of adjuvant endocrine therapy for breast cancer: how long is enough?

Women with estrogen receptor (ER)+ early breast cancer (BC) are at continuing risk of relapse up to at least 15 years after diagnosis, despite being on adjuvant endocrine therapy for approximately 5 years. Extended adjuvant endocrine therapy with an aromatase inhibitor (AI) after 5 years of tamoxifen further reduces the risk of recurrence in postmenopausal women. More recently, continuing tamoxifen for 10 years has also been shown to further reduce the risk of recurrence compared with 5 years. There are no direct comparative data on the relative merits of extended tamoxifen compared with an AI; indirect evidence suggests that an AI may have increased efficacy but a greater adverse effect on quality of life. Results are awaited on the need for continuing front-line adjuvant AIs for more than 5 years. The next challenge is to determine which patients will benefit from this long-term treatment. Currently, tumor size, nodal involvement, and gene expression profile as measured by the PAM50 Risk of Recurrence (ROR) score have all been shown to have prognostic significance for late recurrence beyond 5 years.

Five or more years of adjuvant endocrine therapy in breast cancer: a meta-analysis of published randomised trials

Five years of adjuvant hormonal therapy is the standard of care in early breast cancer (BC) expressing oestrogen receptors (ER+). Prolonged duration of adjuvant endocrine therapy is implemented to prevent recurrence and death; in particular, its carryover effect may prevent very late events. This meta-analysis compares the efficacy of 5 years of hormonal therapy alone with that of additional years of hormonal therapy, in patients with early BC. Randomised trials comparing 5 years versus more than 5 years of hormonal therapy in BC were identified by electronic searches of PubMed, EMBASE, ISI Web of Science and the Cochrane Central Register of Controlled Trials. Meta-analysis was performed using the fixed- or random-effects models. The primary endpoints were overall survival (OS), BC-specific survival (BCSS) and relapse-free survival (RFS) reported as odds ratios (ORs) and 95 % confidence interval (CI). Eight trials, including 29,138 patients, were identified. Overall, in ER+ BCs, extended endocrine therapy beyond 5 years of tamoxifen significantly improved OS (OR, 0.89; 95 % CI 0.80-0.99; P = 0.03), BCSS (OR, 0.78; 95 % CI 0.69-0.9; P = 0.0003) and RFS (OR 0.72; 95 % CI 0.56-0.92; P = 0.01) compared with 5 years of hormonal therapy alone. Loco-regional and distant relapses were reduced by 36 and 13 %, respectively. Compared with 5 years of tamoxifen, additional adjuvant endocrine therapy reduced risk of death and relapse of ER+ BC by ~10 and 30 %, respectively. This strategy should be considered in patients free of disease after 5 years of hormonal therapy.

Impact of premenopausal status at breast cancer diagnosis in women entered on the placebo-controlled NCIC CTG MA17 trial of extended adjuvant letrozole

BACKGROUND

MA17 showed improved outcomes in postmenopausal women given extended letrozole (LET) after completing 5 years of adjuvant tamoxifen.

PATIENTS AND METHODS

Exploratory subgroup analyses of disease-free survival (DFS), distant DFS (DDFS), overall survival (OS), toxic effects and quality of life (QOL) in MA17 were performed based on menopausal status at breast cancer diagnosis.

RESULTS

At diagnosis, 877 women were premenopausal and 4289 were postmenopausal. Extended LET was significantly better than placebo (PLAC) in DFS for premenopausal [hazard ratio (HR) = 0.26, 95% confidence interval (CI) 0.13-0.55; P = 0.0003] and postmenopausal women (HR = 0.67; 95% CI 0.51-0.89; P = 0.006), with greater DFS benefit in those premenopausal (interaction P = 0.03). In adjusted post-unblinding analysis, those who switched from PLAC to LET improved DDFS in premenopausal (HR = 0.15; 95% CI 0.03-0.79; P = 0.02) and postmenopausal women (HR = 0.45; 95% CI 0.22-0.94; P = 0.03).

CONCLUSIONS

Extended LET after 5 years of tamoxifen was effective in pre- and postmenopausal women at diagnosis, and significantly better in those premenopausal. Women premenopausal at diagnosis should be considered for extended adjuvant therapy with LET if menopausal after completing tamoxifen.

Extended adjuvant endocrine therapy in hormone dependent breast cancer: the paradigm of the NCIC-CTG MA.17/BIG 1-97 trial

Early hormone-receptor-positive breast cancer is a chronic relapsing disease that can remain clinically silent for many years. The NCIC-CTG MA.17/BIG 1-97 trial randomized disease-free early breast cancer patients who had received five years of adjuvant tamoxifen to either letrozole or placebo and was the first to demonstrate a benefit with extended endocrine therapy. MA.17/BIG 1-97 was stopped at the first interim analysis because disease free survival was strongly prolonged in the letrozole arm. Subsequent subset analyses and longer follow up have shown that this therapy improved survival across all groups, particularly among women with node-positive disease and those that were pre-menopausal at time of study enrolment. The MA.17/BIG 1-97 study should be considered a paradigm for extended adjuvant endocrine therapy in hormone-receptor-positive early breast cancer.

Putting the cardiovascular safety of aromatase inhibitors in patients with early breast cancer into perspective: a systematic review of the literature

In the adjuvant setting, the third-generation aromatase inhibitors (AIs) anastrozole, letrozole and exemestane are recommended at some point during treatment, either in the upfront, switch after tamoxifen or extended treatment setting after tamoxifen in postmenopausal patients with hormone receptor-positive early breast cancer. AIs have demonstrated superior disease-free survival and overall benefit-to-risk profiles compared with tamoxifen. Potential adverse events, including cardiovascular (CV) side effects, should be considered in the long-term management of patients undergoing treatment with AIs. AIs reduce estrogen levels by inhibiting the aromatase enzyme, thus reducing the levels of circulating estrogen. This further reduction in estrogen levels may potentially increase the risk of developing CV disease. This systematic review evaluated published clinical data for changes in plasma lipoproteins and ischaemic CV events during adjuvant therapy with AIs in patients with hormone receptor-positive early breast cancer. The electronic databases MEDLINE, EMBASE, Derwent Drug File and BIOSIS were searched to identify English-language articles published from January 1998 to 15 April 2011 that reported data on AIs and plasma lipoproteins and/or ischaemic CV events. Overall, available data did not show any definitive patterns or suggest an unfavourable effect of AIs on plasma lipoproteins from baseline to follow-up assessment in patients with hormone receptor-positive early breast cancer. Changes that occurred in plasma lipoproteins were observed soon after initiation of AI therapy and generally remained stable throughout the studies. Available data do not support a substantial risk of ischaemic CV events associated with adjuvant AI therapy; however, studies with longer follow-up are required to better characterize the CV profile of AIs.

Disease-related outcomes with long-term follow-up: an updated analysis of the intergroup exemestane study

PURPOSE

Intergroup Exemestane Study (IES), an investigator-led study in 4,724 postmenopausal patients with early-stage breast cancer has demonstrated clinically important benefits from switching adjuvant endocrine therapy after 2 to 3 years of tamoxifen to exemestane. Now, with longer follow-up, a large number of non-breast cancer-related events have been reported. Exploratory analyses describe breast cancer-free survival (BCFS) and explore incidence and patterns of the different competing events.

PATIENTS AND METHODS

Patients who were disease-free after 2 to 3 years of adjuvant tamoxifen were randomly assigned to continue tamoxifen or switch to exemestane to complete 5 years of adjuvant endocrine therapy. At this planned analysis, the median follow-up was 91 months. Principal analysis focuses on 4,052 patients with estrogen receptor (ER) -positive and 547 with ER-unknown tumors.

RESULTS

In all, 930 BCFS events have been reported (exemestane, 423; tamoxifen, 507), giving an unadjusted hazard ratio (HR) of 0.81 (95% CI, 0.71 to 0.92; P = .001) in favor of exemestane in the ER-positive/ER unknown group. Analysis partitioned at 2.5 years after random assignment showed that the on-treatment benefit of switching to exemestane (HR, 0.60; 95% CI, 0.48 to 0.75; P < .001) was not lost post-treatment, but that there was no additional gain once treatment had ceased (HR, 0.94; 95% CI, 0.80 to 1.10; P = .60). Improvement in overall survival was demonstrated, with 352 deaths in the exemestane group versus 405 deaths in the tamoxifen group (HR, 0.86; 95% CI, 0.75 to 0.99; P = .04). Of these, 222 were reported as intercurrent deaths (exemestane, 107; tamoxifen, 115).

CONCLUSION

The protective effect of switching to exemestane compared with continuing on tamoxifen on risk of relapse or death was maintained for at least 5 years post-treatment and was associated with a continuing beneficial impact on overall survival.

Longer-term outcomes of letrozole versus placebo after 5 years of tamoxifen in the NCIC CTG MA.17 trial: analyses adjusting for treatment crossover

PURPOSE

The interim analysis of the National Cancer Institute of Canada Clinical Trials Group MA.17 trial showed that letrozole was significantly better than placebo in disease-free survival (DFS) for postmenopausal women with hormone receptor-positive breast cancer following about 5 years of tamoxifen therapy. When patients were unblinded, those on placebo were offered letrozole. Longer-term efficacy of letrozole, especially survival, was of particular interest because the median follow-up of the first interim analysis was only 2.5 years. Efficacy was difficult to assess because more than 60% of placebo patients crossed over to letrozole after being unblinded.

PATIENTS AND METHODS

Two statistical approaches were used to adjust for the potential effects of treatment crossover: one was based on the inverse probability of censoring weighted (IPCW) Cox model and the other on a Cox model with time-dependent covariates.

RESULTS

With a median follow-up of 64 months, the hazard ratios (HRs) of letrozole and placebo from the IPCW analyses were HR of 0.52 (95% CI, 0.45 to 0.61; P < .001) for DFS, HR of 0.51 (95% CI, 0.42 to 0.61; P < .001) for distant disease-free survival (DDFS), and HR of 0.61 (95% CI, 0.52 to 0.71; P < .001) for overall survival (OS). The results from the analyses based on the Cox model with time-dependent covariates were similar for letrozole and placebo: HR of 0.58 (95% CI, 0.47 to 0.72; P < .001) for DFS, HR of 0.68 (95% CI, 0.52 to 0.88; P = .004) for DDFS, and HR of 0.76 (95% CI, 0.60 to 0.96; P = .02) for OS.

CONCLUSION

Exploratory analyses based on longer follow-up and adjusting for treatment crossover suggest that extended adjuvant letrozole was superior to placebo in DFS, DDFS, and OS.

Progress in endocrine approaches to the treatment and prevention of breast cancer

Tamoxifen had been the only available hormonal option for the systemic treatment for breast cancer from 1973 to 2000. Enormous efforts have led to the development of potent and selective third generation aromatase inhibitors including anastrozole, letrozole and exemestane. Due to their superior efficacy to tamoxifen, aromatase inhibitors are presently approved as first line agents for the treatment of advanced estrogen receptor (ER) positive breast cancer and adjuvant therapy in early ER positive early breast cancer in postmenopausal women. Selective ER Modulators (SERMS), tamoxifen and raloxifene are the only agents presently used in breast cancer prevention in high risk women and their use has increased substantially over the last decade. Third generations SERMS, lasofoxifene and bazedoxifene have shown significant reduction in bone loss compared to placebo in postmenopausal women and are currently approved in the European Union for the treatment of postmenopausal osteoporosis. This review outlines the current strategies employed in the use of endocrine therapy in the management and prevention of breast cancer.

An updated review on the efficacy of adjuvant endocrine therapies in hormone receptor-positive early breast cancer

The third-generation aromatase inhibitors (AIS) are largely replacing tamoxifen in the adjuvant treatment of early-stage breast cancer in postmenopausal women with hormone receptor–positive tumours. To date, multiple trials have been conducted comparing tamoxifen treatment with an AI, and all have demonstrated improved disease-free survival with AI treatment. Trials have included direct 5-year comparisons between tamoxifen and an AI, switching to an AI within 5 years after initial tamoxifen treatment, or extending treatment with an AI after 5 years of completed tamoxifen treatment. Some of these trials have been completed; others are ongoing; and head-to-head trial comparisons of individual AIS are also in progress. The present article summarizes the data obtained from various clinical trials of hormonal therapy for early breast cancer. It also reviews recent data so as to shed light on the current status of these therapies. The focus is on the efficacy of treatment with an AI. Toxicity is discussed in the second article in this supplement.

Declining incidence of contralateral breast cancer in the United States from 1975 to 2006

PURPOSE

Contralateral breast cancer (CBC) is the most frequent new malignancy among women diagnosed with a first breast cancer. Although temporal trends for first breast cancers have been well studied, trends for CBC are not so well established.

PATIENTS AND METHODS

We examined temporal trends in CBC incidence using US Surveillance, Epidemiology, and End Results database (1975 to 2006). Data were stratified by estrogen receptor (ER) status of the first breast cancer for the available time period (1990+). We estimated the annual percent change (EAPC) in CBC rates using Poisson regression models adjusted for the age at and time since first breast cancer diagnosis.

RESULTS

Before 1985, CBC incidence rates were stable (EAPC, 0.27% per year; 95% CI, -0.4 to 0.9), after which they declined with an EAPC of -3.07% per year (95% CI, -3.5 to -2.7). From 1990 forward, the declines were restricted to CBC after an ER-positive cancer (EAPC, -3.18%; 95% CI, -4.2 to -2.2) with no clear decreases after an ER-negative cancer. Estimated current age-specific CBC rates (per 100/year) after an ER-positive first cancer were: 0.45 for first cancers diagnosed before age 30 years and 0.25 to 0.37 for age 30 years or older. Rates after an ER-negative cancer were higher: 1.26 before age 30 years, 0.85 for age 30 to 35 years, and 0.45 to 0.65 for age 40 or older.

CONCLUSION

Results show a favorable decrease of 3% per year for CBC incidence in the United States since 1985. This overall trend was driven by declining CBC rates after an ER-positive cancer, possibly because of the widespread usage of adjuvant hormone therapies, after the results of the Nolvadex Adjuvant Trial Organisation were published in 1983, and/or other adjuvant treatments.

Comparing guidelines for adjuvant endocrine therapy in postmenopausal women with breast cancer: a coming of age

Following surgery for early breast cancer, the standard of care for postmenopausal women is adjuvant therapy with any combination of radiation therapy, endocrine therapy, chemotherapy and/or targeted therapy. Clinicians rely on many tools, including guidelines, to make these treatment decisions. Such guidelines include the St Gallen consensus statement, the American Society of Clinical Oncology guidelines and the National Comprehensive Cancer Network guidelines, as well as various regional and national guidelines. Recommendations may vary, because different methods and criteria were used to assess the strength of supporting data. This article provides an overview of global guidelines for the adjuvant treatment of breast cancer and points out the major differences. Ongoing changes are highlighted, particularly those regarding the adjuvant endocrine treatment of postmenopausal women with breast cancer. While previous guidelines recommended tamoxifen alone, all major guidelines now recommend using third-generation aromatase inhibitors either in sequence with tamoxifen or as upfront treatment.

American Society of Clinical Oncology clinical practice guideline: update on adjuvant endocrine therapy for women with hormone receptor-positive breast cancer

PURPOSE

To develop evidence-based guidelines, based on a systematic review, for endocrine therapy for postmenopausal women with hormone receptor-positive breast cancer.

METHODS

A literature search identified relevant randomized trials. Databases searched included MEDLINE, PREMEDLINE, the Cochrane Collaboration Library, and those for the Annual Meetings of the American Society of Clinical Oncology (ASCO) and the San Antonio Breast Cancer Symposium (SABCS). The primary outcomes of interest were disease-free survival, overall survival, and time to contralateral breast cancer. Secondary outcomes included adverse events and quality of life. An expert panel reviewed the literature, especially 12 major trials, and developed updated recommendations.

RESULTS

An adjuvant treatment strategy incorporating an aromatase inhibitor (AI) as primary (initial endocrine therapy), sequential (using both tamoxifen and an AI in either order), or extended (AI after 5 years of tamoxifen) therapy reduces the risk of breast cancer recurrence compared with 5 years of tamoxifen alone. Data suggest that including an AI as primary monotherapy or as sequential treatment after 2 to 3 years of tamoxifen yields similar outcomes. Tamoxifen and AIs differ in their adverse effect profiles, and these differences may inform treatment preferences.

CONCLUSION

The Update Committee recommends that postmenopausal women with hormone receptor-positive breast cancer consider incorporating AI therapy at some point during adjuvant treatment, either as up-front therapy or as sequential treatment after tamoxifen. The optimal timing and duration of endocrine treatment remain unresolved. The Update Committee supports careful consideration of adverse effect profiles and patient preferences in deciding whether and when to incorporate AI therapy.

Changes in protein expression after neoadjuvant use of aromatase inhibitors in primary breast cancer: a proteomic approach to search for potential biomarkers to predict response or resistance

OBJECTIVE

Aromatase inhibitors (AI) have been established as a useful hormonal therapy in hormone receptor-expressing breast carcinoma. However, changes in tumor protein expression after exposure to AIs are not necessarily well understood. These changes may provide insight into how breast carcinomas respond or develop into a state of resistance towards AIs, and lead to the discovery of potential biomarkers to predict treatment responses.

METHODS

Post-menopausal breast cancer patients were recruited to receive 3 months treatment with neoadjuvant AI. Carcinoma tissues were collected before and after the use of AIs and protein expression profiles were compared using two-dimensional gel electrophoresis. Protein spots with different levels of expression were identified using mass spectrometry.

RESULTS

A total of 14 matched pairs of tumor tissues were collected. Both up-regulated and down-regulated proteins were selected and identified as follows: heat shock protein 70 protein 2; Cyclin M3, alpha 1 antichymotrypsin precursor; carbonic anhydrase I, cancer antigen 1; SOBP protein; Rho GDP dissociation inhibitor alpha; glyoxalase I with benzyl glutathione inhibitor; lipid-free human apolipoprotein A-I and RAB4A member RAS oncogene family. Among these proteins, heat shock protein 70 demonstrated the most significant positive correlation with clinical response of the patients.

CONCLUSION

After neoadjuvant use of AI, heat shock protein 70 demonstrated the most consistent phenotypic consistency in both up-regulated and down-regulated protein expression levels among the 14 studied pairs of tumor tissue. Other proteins worthwhile exploring were also identified in this study. These proteins could serve as potential predictors for AI response.

Aromatase inhibitors versus tamoxifen as adjuvant hormonal therapy for oestrogen sensitive early breast cancer in post-menopausal women: meta-analyses of monotherapy, sequenced therapy and extended therapy

Adjuvant tamoxifen reduces relapses and prolongs survival in patients with oestrogen sensitive breast cancer. Development of resistance is however common. Tamoxifen can be given for a maximum of five years; although the risk of recurrences remains high after this period. This review examines nine randomised controlled trials including 28,632 women, which studied aromatase inhibitors (AIs) as an alternative to tamoxifen in three treatment settings: monotherapy (instead of tamoxifen), sequenced therapy (tamoxifen is switched to an AI) and extended therapy (following adjuvant tamoxifen). Disease free survival was significantly improved for monotherapy (HR 0.89, [95% CI 0.83-0.96] p = 0.002) and sequenced therapy (HR 0.72, [0.63-0.83] p < 0.00001). There was no difference in overall survival for monotherapy (HR 0.94, [0.82-1.08] p = 0.39) or extended therapy (HR 0.86 [0.79-1.16] p = 0.67). Importantly, overall survival was prolonged for patients who switched from tamoxifen to AI therapy (HR 0.78 95%CI 0.68-0.91, p = 0.001).

Letrozole: a review of its use in the treatment of postmenopausal women with hormone-responsive early breast cancer

Letrozole (Femara) is a third-generation, nonsteroidal aromatase inhibitor. Adjuvant therapy with letrozole is more effective than tamoxifen in postmenopausal women with hormone-responsive early breast cancer, and extended adjuvant therapy with letrozole after the completion of adjuvant tamoxifen therapy is more effective than placebo in this patient population; letrozole is generally well tolerated. Ongoing trials will help answer outstanding questions regarding the optimal duration of letrozole therapy in early breast cancer and its efficacy compared with other third-generation aromatase inhibitors such as anastrozole. In the meantime, letrozole should be considered a valuable option in the treatment of postmenopausal women with hormone-responsive early breast cancer, both as adjuvant and extended adjuvant therapy.

Patterns of care in Dutch postmenopausal patients with hormone-sensitive early breast cancer participating in the Tamoxifen Exemestane Adjuvant Multinational (TEAM) trial

BACKGROUND

The Tamoxifen and Exemestane Adjuvant Multinational (TEAM) trial investigates the efficacy and safety of adjuvant exemestane alone and in sequence after tamoxifen in postmenopausal women with hormone-sensitive early breast cancer. As there was a nationwide participation in The Netherlands, we studied the variations in patterns of care in the Comprehensive Cancer Centre Regions (CCCRs) and compliance with national guidelines.

METHODS

Clinicopathological characteristics, carried out local treatment strategies and adjuvant chemotherapy data were collected.

RESULTS

From 2001 to January 2006, 2754 Dutch patients were randomised to the study. Mean age of patients was 65 years (standard deviation 9). Tumours were < or =2 cm in 46% (within CCCRs 39%-50%), node-negative disease varied from 25% to 45%, and PgR status was determined in 75%-100% of patients. Mastectomy was carried out in 55% (45%-70%), sentinel lymph node procedure in 68% (42%-79%) and axillary lymph node dissections in 77% (67%-83%) of patients, all different between CCCRs (P < 0.0001). Adjuvant chemotherapy was given in 15%-70% of eligible patients (P < 0.001).

DISCUSSION

In spite of national guidelines, breast cancer treatment on specific issues widely varied between the various Dutch regions. These data provide valuable information for breast cancer organisations indicating (lack of) guideline adherence and areas for breast cancer care improvement.

Long-term efficacy and safety of letrozole for the adjuvant treatment of early breast cancer in postmenopausal women: a review

Aromatase inhibitors (AIs) are becoming more widely used than tamoxifen as adjuvant hormonal therapy for postmenopausal women (PMW) with early breast cancer (EBC). It is clear that these drugs offer important efficacy benefits over tamoxifen and differ from tamoxifen in their safety profile. The accepted strategies for adjuvant AI therapy include initial adjuvant treatment following surgery, switching and/or sequencing from prior tamoxifen, and extended adjuvant therapy following the full 5 years of tamoxifen treatment. Among the available AIs, letrozole has been evaluated in large, well-controlled, double-blind clinical trials in the initial adjuvant, extended adjuvant, and more recently, the sequential adjuvant settings. Letrozole is the most potent of the AIs and provides near complete suppression of plasma estrogens in PMW. Letrozole also significantly reduces the occurrence of early distant metastases, the most lethal type of recurrence event, which can lead to improved survival. Clinical comparisons of letrozole with both tamoxifen and placebo have also provided important long-term safety data on the use of AIs as adjuvant therapy in PMW with EBC. The weight of clinical evidence indicates that letrozole is a safe and effective option for adjuvant hormonal therapy across all three AI treatment settings.

Tamoxifen: the drug that came in from the cold

Despite the perception of many oncologists that tamoxifen is an inferior drug, and should be substituted by an aromatase inhibitor in post-menopausal women, the current evidence strongly supports the view that AIs should be used 2-3 years after tamoxifen to achieve the maximal overall survival (OS) advantage.

Extended adjuvant endocrine therapy in breast cancer: current status and future directions

Women with hormone receptor-positive breast cancer have traditionally been treated with 5 years of adjuvant tamoxifen to reduce their risk of subsequent recurrent disease. Among those who experience subsequent disease recurrence, the majority do so after 5 years, suggesting that longer durations of endocrine therapy might be beneficial. Two options tested include longer tamoxifen and, in postmenopausal women, a switch to an aromatase inhibitor (AI). In the National Cancer Institute of Canada Cooperative Trials Group MA.17 trial, we tested the AI letrozole given to postmenopausal women for 5 years after tamoxifen as extended adjuvant therapy because of its efficacy in patients with advanced breast cancer in progression on previous tamoxifen. The first interim analysis (median, 2.4 patient years) showed substantial benefits from letrozole, and all patients were unblinded and offered the option of letrozole. Despite two thirds of the patients crossing over to letrozole, an intent-to-treat analysis at 54 months' follow-up continued to demonstrate the strong beneficial effect of extended adjuvant letrozole. Furthermore, significant benefit was demonstrated among patients who had been randomized to placebo but elected to take letrozole after a prolonged washout from previous tamoxifen (late extended adjuvant therapy). A trial examining the merits of > 5 years of treatment with an AI, MA.17R, is ongoing, as are a number of other trials of duration of therapy. This article reviews results from MA.17 and the design of these trials of duration.