Response Rate as an Endpoint in Clinical Trials

Application of the ESMO Magnitude of Clinical Benefit Scale to assess the clinical benefit of antibody drug conjugates in solid cancer: a systematic descriptive analysis of phase III and pivotal phase II trials

OBJECTIVE

The aim of this study was to assess the clinical benefit value of approved antibody drug conjugates (ADCs) for solid tumours using the European Society for Medical Oncology Magnitude of Clinical Benefit Scale (ESMO-MCBS) V.1.1.

DESIGN

Systematic descriptive analysis.

DATA SOURCES

PubMed was searched for publications from 1 January 2000 to 18 October 2023.

ELIGIBILITY CRITERIA

We included the phase III randomised controlled trials or phase II pivotal trials leading to approval of ADCs in solid tumours.

DATA EXTRACTION AND SYNTHESIS

Two independent reviewers extracted data and discrepancies were resolved by consensus in the presence of a third investigator.

RESULTS

ESMO-MCBS Scores were calculated for 16 positive clinical trials of eight ADCs, which were first approved by the US Food and Drug Administration (FDA), the European Medicines Agency (EMA), the China National Medical Products Administration and the Japanese Pharmaceuticals and Medical Devices Agency for solid cancers. Among 16 trials, 4 (25%) met the ESMO-MCBS benefit threshold grade, while 12 (75%) of the regimens did not meet the ESMO-MCBS benefit threshold grade. 5 (31%) of the 16 trials had no published scorecard on the ESMO website due to the approval by other jurisdictions but not by the FDA or EMA. Discrepancies between our results and the ESMO scorecard were observed in 4 (36%) of 11 trials, mostly owing to integration of more recent data.

CONCLUSIONS

ESMO-MCBS is an important tool for assessing the clinical benefit of cancer drugs, but not all drugs met the meaningful benefit threshold.

Single-arm trials supporting the approval of anticancer medicinal products in the European Union: contextualization of trial results and observed clinical benefit

BACKGROUND

Single-arm trials (SATs) can sometimes be used to support marketing authorization of anticancer medicinal products in the European Union. The level and durability of antitumor activity of the product as well as context are important aspects to determine the relevance of trial results. The aim of this study is to provide details on the contextualization of trial results and to evaluate the magnitude of benefit of medicinal products approved based on SATs.

MATERIALS AND METHODS

We focused on anticancer medicinal products for solid tumors approved on the basis of SAT results (2012-2021). Data were retrieved from European public assessment reports and/or published literature. The benefit of these medicinal products was evaluated via the European Society for Medical Oncology (ESMO)-Magnitude of Clinical Benefit Scale (MCBS).

RESULTS

Eighteen medicinal products were approved based on 21 SATs-few medicinal products were supported by >1 SAT. For the majority of clinical trials, a clinically relevant treatment effect was (pre)specified (71.4%) and most often an accompanying sample size calculation was provided. For 10 studies, each testing a different medicinal product, a justification for the threshold for a clinically relevant treatment effect could be identified. At least 12 out of 18 applications included information to facilitate the contextualization of trial results, including six supportive studies. Of the pivotal SATs analyzed (n = 21), three were assigned an ESMO-MCBS score of 4, which corresponds to 'substantial' benefit.

CONCLUSIONS

The clinical relevance of the treatment effects shown by medicinal products for solid tumors tested in SATs is dependent on the effect size and context. To better facilitate regulatory decision making, prespecifying and motivating a clinically relevant effect and aligning the sample size to that effect is important. External controls may facilitate in the contextualization process, but the associated limitations must be addressed.

Tumor Response, Disease Control, and Progression-Free Survival as Surrogate Endpoints in Trials Evaluating Immune Checkpoint Inhibitors in Advanced Non-Small Cell Lung Cancer: Study- and Patient-Level Analyses

Background: To assess the usefulness of tumor response and progression-free survival (PFS) as surrogates for overall survival (OS) in non-small cell lung cancer (NSCLC) trials with immune checkpoint inhibitors (ICI), which have not been confirmed. Methods: Patient- and trial-level analyses were performed. The Response Evaluation Criteria in Solid Tumors was preferred for image assessment. For trial-level analysis, surrogacy was assessed using the weighted rank correlation coefficient (r) following "reciprocal duplication." This method duplicates all plots as if the experimental and the reference arms were switched. Monte Carlo simulations were performed for evaluating this method. Results: A total of 3312 cases were included in the patient-level analysis. Patients without response (first line (1L): hazard ratio (HR) 1.95, 95% confidence interval (CI) 1.71-2.23; second or later line (2L-): HR 4.22, 95% CI 3.22-5.53), without disease control (1L: HR 4.34, 95% CI 3.82-4.94; 2L-: HR 3.36, 95% CI 2.96-3.81), or with progression during the first year (1L: HR 3.42, 95% CI 2.60-4.50; 2L-: HR 3.33, 95% CI 2.64-4.20), had a higher risk of death. Systematic searches identified 38 RCTs including 17,515 patients for the study-level analysis. Odds ratio in the objective response rate (N = 38 × 2, r = -0.87) and HR in PFS (N = 38 × 2, r = 0.85) showed an excellent association with HR in overall survival, while this effect was not observed in the disease control rate (N = 26 × 2, r = -0.03). Conclusions: Objective response rate and PFS are reasonable surrogates for OS in NSCLC trials with ICI.

Short-term and long-term prognostic value of histological response and intensified chemotherapy in osteosarcoma: a retrospective reanalysis of the BO06 trial

OBJECTIVES

Cure rate models accounting for cured and uncured patients, provide additional insights into long and short-term survival. We aim to evaluate the prognostic value of histological response and chemotherapy intensification on the cure fraction and progression-free survival (PFS) for the uncured patients.

DESIGN

Retrospective analysis of a randomised controlled trial, MRC BO06 (EORTC 80931).

SETTING

Population-based study but proposed methodology can be applied to other trial designs.

PARTICIPANTS

A total of 497 patients with resectable highgrade osteosarcoma, of which 118 were excluded because chemotherapy was not started, histological response was not reported, abnormal dose was reported or had disease progression during treatment.

INTERVENTIONS

Two regimens with the same anticipated cumulative dose (doxorubicin 6×75 mg/m²/week; cisplatin 6×100 mg/m²/week) over different time schedules: every 3 weeks in regimen-C and every 2 weeks in regimen-DI.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome is PFS computed from end of treatment because cure, if it occurs, may happen at any time during treatment. A mixture cure model is used to study the effect of histological response and intensified chemotherapy on the cure status and PFS for the uncured patients.

RESULTS

Histological response is a strong prognostic factor for the cure status (OR 3.00, 95% CI 1.75 to 5.17), but it has no clear effect on PFS for the uncured patients (HR 0.78, -95% CI 0.53 to 1.16). The cure fractions are 55% (46%-63%) and 29% (22%-35%), respectively, among patients with good and poor histological response (GR, PR). The intensified regimen was associated with a higher cure fraction among PR (OR 1.90, 95% CI 0.93 to 3.89), with no evidence of effect for GR (OR 0.78, 95% CI 0.38 to 1.59).

CONCLUSIONS

Accounting for cured patients is valuable in distinguishing the covariate effects on cure and PFS. Estimating cure chances based on these prognostic factors is relevant for counselling patients and can have an impact on treatment decisions.

TRIAL REGISTRATION NUMBER

ISRCTN86294690.

Toward developing a metastatic breast cancer treatment strategy that incorporates history of response to previous treatments

Background

Information regarding response to past treatments may provide clues concerning the classes of drugs most or least likely to work for a particular metastatic or neoadjuvant early stage breast cancer patient. However, currently there is no systematized knowledge base that would support clinical treatment decision-making that takes response history into account.

Methods

To model history-dependent response data we leveraged a published in vitro breast cancer viability dataset (84 cell lines, 90 therapeutic compounds) to calculate the odds ratios (log (OR)) of responding to each drug given knowledge of (intrinsic/prior) response to all other agents. This OR matrix assumes (1) response is based on intrinsic rather than acquired characteristics, and (2) intrinsic sensitivity remains unchanged at the time of the next decision point. Fisher’s exact test is used to identify predictive pairs and groups of agents (BH p < 0.05). Recommendation systems are used to make further drug recommendations based on past ‘history’ of response.

Results

Of the 90 compounds, 57 have sensitivity profiles significantly associated with those of at least one other agent, mostly targeted drugs. Nearly all associations are positive, with (intrinsic/prior) sensitivity to one agent predicting sensitivity to others in the same or a related class (OR > 1). In vitro conditional response patterns clustered compounds into five predictive classes: (1) DNA damaging agents, (2) Aurora A kinase and cell cycle checkpoint inhibitors; (3) microtubule poisons; (4) HER2/EGFR inhibitors; and (5) PIK3C catalytic subunit inhibitors. The apriori algorithm implementation made further predictions including a directional association between resistance to HER2 inhibition and sensitivity to proteasome inhibitors.

Conclusions

Investigating drug sensitivity conditioned on observed sensitivity or resistance to prior drugs may be pivotal in informing clinicians deciding on the next line of breast cancer treatments for patients who have progressed on their current treatment. This study supports a strategy of treating patients with different agents in the same class where an associated sensitivity was observed, likely after one or more intervening treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07912-7.

Response Rates and Durations of Response for Biomarker-Based Cancer Drugs in Nonrandomized Versus Randomized Trials

BACKGROUND

Many new targeted cancer drugs have received FDA approval based on durable responses in nonrandomized controlled trials (non-RCTs). The goal of this study was to evaluate whether the response rates (RRs) and durations of response (DoRs) of targeted cancer drugs observed in non-RCTs are consistent when these drugs are tested in RCTs.

METHODS

We used the FDA's Table of Pharmacogenomic Biomarkers in Drug Labeling to identify cancer drugs that were approved based on changes in biomarker endpoints through December 2017. We then identified the non-RCTs and RCTs for these drugs for the given indications and extracted the RRs and DoRs. We compared the RRs and median DoR in non-RCTs versus RCTs using the ratio of RRs and the ratio of DoRs, defined as the RRs (or DoRs) in non-RCTs divided by the RRs (or DoRs) in RCTs. The ratio of RRs or DoRs was pooled across the trial pairs using random-effects meta-analysis.

RESULTS

Of the 21 drug-indication pairs selected, both non-RCTs and RCTs were available for 19. The RRs and DoRs in non-RCTs were greater than those in RCTs in 63% and 87% of cases, respectively. The pooled ratio of RRs was 1.06 (95% CI, 0.95-1.20), and the pooled ratio of DoRs was 1.17 (95% CI, 1.03-1.33). RRs and DoRs derived from non-RCTs were also poor surrogates for overall survival derived from RCTs.

CONCLUSIONS

The RRs were not different between non-RCTs and RCTs of cancer drugs approved based on changes to a biomarker, but the DoRs in non-RCTs were significantly higher than in RCTs. Caution must be exercised when approving or prescribing targeted drugs based on data on durable responses derived from non-RCTs, because the responses could be overestimates and poor predictors of survival benefit.

Challenges in translating endpoints from trials to observational cohort studies in oncology

Clinical trials are considered the gold standard for examining drug efficacy and for approval of new drugs. Medical databases and population surveillance registries are valuable resources for post-approval observational research, which are increasingly used in studies of benefits and risk of new cancer drugs. Here, we address the challenges in translating endpoints from oncology trials to observational studies. Registry-based cohort studies can investigate real-world safety issues – including previously unrecognized concerns – by examining rare endpoints or multiple endpoints at once. In contrast to clinical trials, observational cohort studies typically do not exclude real-world patients from clinical practice, such as old and frail patients with comorbidity. The observational cohort study complements the clinical trial by examining the effectiveness of interventions applied in clinical practice and by providing evidence on long-term clinical outcomes, which are often not feasible to study in a clinical trial. Various endpoints can be included in clinical trials, such as hard endpoints, soft endpoints, surrogate endpoints, and patient-reported endpoints. Each endpoint has it strengths and limitations for use in research studies. Endpoints used in oncology trials are often not applicable in observational cohort studies which are limited by the setting of standard clinical practice and by non-standardized endpoint determination. Observational studies can be more helpful moving research forward if they restrict focus to appropriate and valid endpoints.

Progression-Free Survival, Response Rate, and Disease Control Rate as Predictors of Overall Survival in Phase III Randomized Controlled Trials Evaluating the First-Line Chemotherapy for Advanced, Locally Advanced, and Recurrent Non-Small Cell Lung Carcinoma

INTRODUCTION

Recent improvements in chemotherapy agents have prolonged postprogression survival of non-small cell lung cancer. Thus, primary outcomes other than overall survival (OS) have been frequently used for recent phase III trials to obtain quick results. However, no systematic review had assessed whether progression-free survival (PFS), response rate (RR), and disease control rate (DCR) can serve as surrogates for OS at the trial level in the phase III first-line chemotherapy setting.

METHODS

We included phase III randomized clinical trials (RCTs) comparing two arms that were reported as a full article regardless of their primary end point. We included only RCTs that evaluated chemonaive patients with advanced, locally advanced, or metastatic non-small cell lung cancer and were published after January 1, 2005. We systematically searched four public electronic databases. Two investigators independently screened and scrutinized candidate articles. How surrogate outcomes represented hazard ratios (HRs) for OS was examined.

RESULTS

Among 1907 articles, we ultimately found 44 eligible articles covering 22,709 subjects. HR for PFS, median PFS in the experimental arm minus median PFS in the control arm in months, OR for RR (ORrr), and OR for DCR were evaluated in 34, 35, 44, and 35 RCTs, respectively. HR for OS (HRos), median PFS in the experimental arm minus median PFS in the control arm, ORrr, and OR for DCR had weighted Spearman's rank correlation coefficients with an HRos of 0.496, 0.477, 0.570, and 0.470, respectively; the standardized weighted regression coefficients were 0.439, -0.376, -0.605, and -0.381, respectively; and the adjusted weighted coefficients of determination were 0.224, 0.161, 0.350, and 0.176, respectively.

CONCLUSIONS

ORrr, followed by HRpfs, had the strongest association with HRos at the trial level. However, these measures were not strong enough to replace OS.

Statistical considerations and endpoints for clinical lung cancer studies: Can progression free survival (PFS) substitute overall survival (OS) as a valid endpoint in clinical trials for advanced non-small-cell lung cancer?

In the last decades significant progress has been achieved in the biological understanding of non-small-cell lung cancer (NSCLC) and its tumor heterogeneity has become more evident. The identification of novel tumor targets with different pathways has stimulated the search for anti-tumor agents with a specific target directed mode of action, stipulating the need of testing these agents in clinical trials with an appropriate choice of the study endpoint. Gold standard as an endpoint has been so far overall survival (OS). By definition there are 3 categories of classical endpoints applied generally in clinical lung cancer studies: survival time endpoints, symptom endpoints, and endpoints relying on patients' reporting. Beside classical endpoints like OS which are tending to show the direct clinical effect of treatment, efforts have been taken to substitute these classical endpoints by surrogates. As a surrogate candidate for OS progression-free survival (PFS) should have the inherent considerable advantage, that it can detect subpopulations with longer PFS intervals early. Based on the (sub-) population treated and having in mind the risk-benefit profile of the drug under consideration, PFS can be considered for regulatory decision making. If accompanied by some independent measures like quality of life or treatment toxicity, PFS should be able to cover the clinical benefit achieved by treatment. Selecting PFS as primary endpoint in Phase III trials of advanced NSCLC may be based on a number of questions such as: Does the definition of PFS fit into the setting used by other trials? Are there accepted consensus standards? Are there consistent surveillance intervals? Is validation for each agent group planned? Is the incremental improvement of PFS big enough (≥30%)? And are there some additional measures to confine clinical benefit? OS is still accepted as the gold standard in trials investigating advanced NSCLC. OS is easy to measure and precise but it may be difficult to interpret if treatment action takes place only in a small subinterval of overall survival. PFS with some additional measures has become attractive when it seems advisable to make study results available earlier. Candidates for supporting PFS as "additional measures" may be treatment toxicity and quality of life measures. PFS allows a more precise detection and attribution to effects of the investigational treatment without being compromised by subsequent treatments. Therefore "enriched PFS" can be considered as an alternative primary endpoint replacing OS in studies investigating advanced NSCLC. The endpoint selection process should always be performed carefully considering all true and surrogate endpoint options in respect to the hypotheses to be proven.

Role of pemetrexed in advanced non-small-cell lung cancer: meta-analysis of randomized controlled trials, with histology subgroup analysis

PURPOSE

Platinum-based regimens represent the standard first-line treatment for non-small-cell lung cancer (nsclc). However, newer data have established a role for pemetrexed in the treatment of this disease. Such data suggest that histology represents a determining factor in the selection of treatment.

METHODS

We undertook a systematic review of the literature for randomized controlled trials that compared the efficacy of pemetrexed with that of other treatments in advanced nsclc. Data and study quality were assessed according to published guidelines.

RESULTS

We identified five trials that compared pemetrexed with other treatments or with placebo. Overall survival for patients treated with pemetrexed was superior to that with other treatments: hazard ratio (hr): 0.89; 95% confidence interval (ci): 0.80 to 0.99. The survival benefit was limited to patients with non-squamous histology: hr: 0.82; 95% ci: 0.73 to 0.91. Pemetrexed was inferior to other chemotherapy options in patients with squamous histology: hr: 1.19; 95% ci: 0.99 to 1.43.

CONCLUSIONS

Compared with other chemotherapy agents, pemetrexed is more effective for the treatment of nsclc in patients with non-squamous histology.

Reporting trends of outcome measures in phase II and phase III trials conducted in advanced-stage non-small-cell lung cancer

BACKGROUND

The methodology of conducting clinical trials in lung cancer has been challenged by the particular characteristics of new targeted agents. Thus, the choice of correct outcome measures and selection of best study designs are essential. We assessed the trends in reporting of outcome measures in phase II and phase III trials conducted in advanced non-small-cell lung cancer (NSCLC) patients.

METHODS

Data from September 2000 to September 2012 were extracted from the ClinicalTrials.gov database, and a descriptive-comparative analysis was performed to evaluate outcome-measures reporting for the two phases.

RESULTS

We identified 459 phase II and 128 phase III trials that met our inclusion criteria. The frequently reported primary outcomes in phase II trials were progression-free survival (PFS; 32%), response rate (RR; 21.4%), and safety and toxicity (adverse events [AEs]; 14.6%). In contrast, overall survival (OS; 60.9%) and PFS (26.6%) were frequently reported primary outcomes in phase III trials. AEs were reported as a secondary outcome measure in 50.1 and 64.8% of phase II and phase III trials, respectively. Improvement in quality of life was identified as a secondary outcome measure significantly more frequently in phase III than in phase II trials.

CONCLUSIONS

Our study identified recent trends in reports of outcome measures in advanced-stage NSCLC phase II and phase III trials. The outcomes of this study can be valuable for investigators with minimal or some experience in the field of oncology who are conducting clinical research.

Opportunities and pitfalls of cancer imaging in clinical trials

Cancer treatment strategies have changed considerably over the past two decades, with increasing emphasis on cancer-specific biological therapies. This situation has led to the incorporation of biomarkers, including those obtained by medical imaging, into trial designs to better understand mechanisms of action and, hopefully, to provide early evidence of treatment efficacy at a molecular or physiological level. Unlike blood tests and tissue samples, an imaging biomarker allows assessment of treatment in the whole tumor, in all tumors in the body, and at multiple time points. This situation has increased the complexity of clinical trials, as each imaging modality has issues related to cost, ease of use, patient compatibility, data analysis, and interpretation. This article reviews strengths and limitations of the current imaging methods available in clinical cancer trials, including MRI, CT, PET, and ultrasonography. The information gained by each test, and the difficulties in acquiring the data and interpreting it are also discussed in order to help researchers plan imaging in clinical trials and interpret data from such studies.

Making the investigational oncology pipeline more efficient and effective: are we headed in the right direction?

Advances in our knowledge of the molecular mechanisms involved in cancer biology have contributed to an increase in novel target-specific oncology therapeutics. Unfortunately, clinical development of new drugs is an expensive and slow process, and the patient and financial resources needed to study the vast number of potential therapies are limited, requiring novel approaches to clinical trial design and patient recruitment. In addition, traditional efficacy endpoints may not be adequate to fully determine the therapeutic worth of the new classes of targeted agents. In this new era of drug development, it has become increasingly clear that new clinical trial design paradigms that examine nontraditional endpoints have become necessary to assist in prioritizing the development of the most promising agents. It is also vital that individual patient management be considered, and the subpopulations of patients most likely to derive benefit or experience harm from a new therapy be identified as early as possible. Phase I and II clinical trials allow investigators doing clinical research the opportunity to define these critical endpoints and subpopulations early on, before conducting large-scale randomized phase III clinical trials, which require an abundance of financial and patient resources.

Profiling of high-grade central osteosarcoma and its putative progenitor cells identifies tumourigenic pathways

Background:

Osteosarcoma is the most prevalent primary malignant bone tumour in children and young adults, with poor survival in 40% of patients. To identify the signalling pathways involved in tumourigenesis, we compared gene expression in osteosarcoma with that in its presumed normal counterparts.

Methods:

Genome-wide expression profiles were generated from 25 high-grade central osteosarcoma prechemotherapy biopsies, 5 osteoblastomas, 5 mesenchymal stem cell (MSC) populations and these same MSCs differentiated into osteoblasts. Genes that were differentially expressed were analysed in the context of the pathways in which they function using the GenMAPP programme.

Results:

MSCs, osteoblasts, osteoblastomas and osteosarcomas clustered separately and thousands of differentially expressed genes were identified. The most significantly altered pathways are involved in cell cycle regulation and DNA replication. Several upstream components of the Wnt signalling pathway are downregulated in osteosarcoma. Two genes involved in degradation of β-catenin protein, the key effectors of Wnt signalling, Axin and GSK3-β, show decreased expression, suggesting that Wnt signalling is no longer under the control of regular signals. Comparing benign osteoblastomas with osteosarcomas identified cell cycle regulation as the most prominently changed pathway.

Conclusion:

These results show that upregulation of the cell cycle and downregulation of Wnt signalling have an important role in osteosarcoma genesis. Gene expression differences between highly malignant osteosarcoma and benign osteoblastoma involve cell cycle regulation.

Stathmin and tubulin expression and survival of ovarian cancer patients receiving platinum treatment with and without paclitaxel

BACKGROUND

Paclitaxel interacts with microtubules to exert therapeutic effects. Molecules that affect microtubule activity, such as betaIII-tubulin and stathmin, may interfere with the treatment. In this study, the authors analyzed betaIII-tubulin and stathmin expression in ovarian tumors and examined their associations with treatment response and patient survival.

METHODS

The study included 178 patients with epithelial ovarian cancer who underwent cytoreductive surgery followed by platinum-based chemotherapy; of these patients, 75 also received paclitaxel. Fresh tumor samples that were collected at surgery were analyzed for messenger RNA expression of betaIII-tubulin and stathmin using real-time polymerase chain reaction analysis. Associations of these molecules with treatment response, disease progression, and overall survival were evaluated.

RESULTS

High stathmin expression was associated with worse disease progression-free and overall survival compared with low stathmin expression. This association was independent of patient age, disease stage, tumor grade, histology, and residual tumor size and was observed in patients who received platinum plus paclitaxel, but not in patients who received platinum without paclitaxel, suggesting that stathmin expression in tumor tissue may interfere with paclitaxel treatment. Similar effects were not observed for betaIII-tubulin, although high betaIII-tubulin expression was associated with disease progression among patients who received platinum without paclitaxel. No associations were observed between treatment response and tubulin or stathmin expression. Expression levels of betaIII-tubulin and stathmin were correlated significantly.

CONCLUSIONS

High stathmin expression predicted an unfavorable prognosis in patients with ovarian cancer who received paclitaxel and platinum chemotherapy. This finding supports the possibility that stathmin may interfere with paclitaxel treatment, leading to a poor prognosis for patients with ovarian cancer.

Neoadjuvant chemotherapy for operable breast cancer

Background

Neoadjuvant chemotherapy for early breast cancer can avoid mastectomy by shrinkage of tumour volume. This review assesses the effectiveness of neoadjuvant chemotherapy on clinical outcome.

Methods

All randomized trials comparing neoadjuvant and adjuvant chemotherapy for early breast cancer were reviewed systematically and meta-analyses were performed.

Results

Fourteen studies randomizing 5500 women were eligible for analysis. Overall survival was equivalent in both groups. In the neoadjuvant group, the mastectomy rate was lower (relative risk 0·71 (95 per cent confidence interval (c.i.) 0·67 to 0·75)) without hampering local control (hazard ratio 1·12 (95 per cent c.i. 0·92 to 1·37)). Neoadjuvant chemotherapy was associated fewer adverse effects.

Conclusion

Neoadjuvant chemotherapy is an established treatment option for early breast cancer.