Lessons in precision oncology from neoadjuvant endocrine therapy trials in ER+ breast cancer

Dalpiciclib plus aromatase inhibitor versus neoadjuvant chemotherapy for ER-positive, HER2-negative breast cancer

Background

The combination of cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i) with endocrine therapy (ET) has emerged as an effective alternative to neoadjuvant chemotherapy (NCT) for patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2 (HER2) -negative breast cancer (BC). This single-center study retrospectively evaluated the efficacy and safety of dalpiciclib combined with an aromatase inhibitor (AI) compared to NCT.

Methods

The clinicopathological data and treatment details of patients with HR+ HER2 negative BC who underwent either neoadjuvant endocrine therapy (NET) or NCT were collected from the Fourth Hospital of Hebei Medical University. The primary endpoint of the study was the Residual Cancer Burden (RCB), while secondary endpoints included breast pathological complete response (bpCR), clinical response rates (ORR), proliferation markers, and safety profiles.

Results

Between May 2022 and June 2023, a total of 36 patients were treated with dalpiciclib plus AI, while 137 patients received NCT for the final analysis. Prior to propensity score matching (PSM), the rates of RCB 0 were 0% in the NET group and 7.3% in the NCT group (p=0.205). The rates of bpCR were 2.8% for the NET group and 13.1% for the NCT group (p=0.142). The ORR was comparable between the two groups (p=0.397), as were the rates of BCS (p=0.608). Both treatment groups demonstrated significant reductions in Ki-67 levels, although the extent of reduction was similar (p=0.174). Notably, a Ki-67 level of ≤ 10% post-treatment was more prevalent in the NET group (p<0.0001). Only two patients in the NET group achieved a Preoperative Endocrine Prognostic Index (PEPI) 0 score. The incidence of grade 3-4 toxicities was significantly higher in the NCT group compared to the NET group (p<0.05). Following PSM, patients treated with dalpiciclib plus AI exhibited comparable clinical responses and a safety advantage relative to those receiving NCT.

Conclusion

This study indicates that the combination of dalpiciclib and AI elicits comparable responses and demonstrates improved safety profiles when compared to NCT in patients with HR+ HER2 negative breast tumors. Furthermore, RCB and pCR may not serve as optimal endpoints for evaluating the efficacy of CDK4/6i-based NET.

PKMYT1 Is a Marker of Treatment Response and a Therapeutic Target for CDK4/6 Inhibitor-Resistance in ER+ Breast Cancer

Endocrine therapies (ET) with cyclin-dependent kinase 4/6 (CDK4/6) inhibition are the standard treatment for estrogen receptor-α-positive (ER+) breast cancer, however drug resistance is common. In this study, proteogenomic analyses of patient-derived xenografts (PDXs) from patients with 22 ER+ breast cancer demonstrated that protein kinase, membrane-associated tyrosine/threonine one (PKMYT1), a WEE1 homolog, is estradiol (E2) regulated in E2-dependent PDXs and constitutively expressed when growth is E2-independent. In clinical samples, high PKMYT1 mRNA levels associated with resistance to both ET and CDK4/6 inhibition. The PKMYT1 inhibitor lunresertib (RP-6306) with gemcitabine selectively and synergistically reduced the viability of ET and palbociclib-resistant ER+ breast cancer cells without functional p53. In vitro the combination increased DNA damage and apoptosis. In palbociclib-resistant, TP53 mutant PDX-derived organoids and PDXs, RP-6306 with low-dose gemcitabine induced greater tumor volume reduction compared to treatment with either single agent. Our study demonstrates the clinical potential of RP-6306 in combination with gemcitabine for ET and CDK4/6 inhibitor resistant TP53 mutant ER+ breast cancer.

Neoadjuvant endocrine therapy in ER-positive breast cancer: evolution, indication, and tailored treatment strategy

In recent years, endocrine therapy (ET), an effective systemic treatment for the management of estrogen receptor (ER)-positive breast cancers, has regained interest as a neoadjuvant therapy based on evidence that ET can fulfill the aim of neoadjuvant systemic treatment for tumor shrinkage as well as elucidate important clinical information on endocrine sensitivity that enables the prognostication of patients. Moreover, neoadjuvant endocrine therapy (NET) potentially provides an opportunity for early assessment of the clinical efficacy of novel agents. Furthermore, recently reported trials have generated evidence for a more tailored approach for perioperative management of ER-positive breast cancer using clinical and molecular biomarkers, and this has provided a rationale that enables the broadening of clinical indications for NET. This review discusses the current evidence for NET, the evolution of NET trials, clinical indications, and NET-based treatment strategies.

Breast cancer gene expression signatures: development and clinical significance-a narrative review

Background and Objective

Breast cancer gene expression signatures are developing rapidly and are expected to better understand the intrinsic features of the tumor, and also to optimize the treatment strategy in clinical practice. This review is to summarize the controversy and consensus in clinical practice of gene expression signatures, and to provide our perspective on these issues as well as recommendation for future direction.

Methods

We reviewed English publications in PubMed related to breast cancer gene expression signatures from 2002 to 2022.

Key Content and Findings

Five mature commercial gene expression signatures: Oncotype, MammaPrint, Prosigna/PAM50, EndoPredict and Breast Cancer Index (BCI) are available to provide the prognostic and predictive assessment. Although they could help to evaluate the risk of recurrence and to predict the benefits of certain treatments, their applications remain challenging. Treatment decisions should be determined by a combination of related clinical pathological factors in clinical practice.

Conclusions

Gene expression signatures could assist in the determination of the adjuvant therapy of early-stage breast cancer. The prospective randomized clinical trials showed that chemotherapy may be exempted in low-risk patients. More sufficient data are expected for the application in radiotherapy, extended endocrine therapy, and neoadjuvant treatment. The treatment cannot be determined by a single factor but by comprehensive assessments of clinicopathological factors, test purpose, and cost-effectiveness. Patients will benefit from personalized treatments with the publication of further evidence.

Study protocol: Randomized, open-label, non-inferiority clinical trial for evaluating the clinical and pathological response rates to neoadjuvant hormone therapy and chemotherapy in patients with luminal-subtype breast tumors

Background

Despite neoadjuvant hormone therapy (NHT) is being underused, it is an effective treatment for luminal tumors at a lower cost and with fewer side effects compared to those associated with neoadjuvant chemotherapy (NCT). The lack of robust comparative data between NHT and NCT is a factor that limits its use in clinical practice.

Methods

This study will be a randomized, open-label, non-inferiority clinical trial. Patients diagnosed with HER2-negative luminal-subtype breast cancer will be identified at the time of diagnosis. Menopausal patients randomized for NHT should receive anastrozole for at least six months. Premenopausal women should receive anastrozole associated with subcutaneous goserelin acetate every 12 weeks for at least six months. Patients randomized for NCT will receive a standard institutional regimen based on anthracyclines and taxanes. Sample size was calculated considering the CPS + EG as a method for evaluating response and prognosis, where a score <3 was defined as good. The non-inferiority margin for NHT was set at 15%. The study considered a power of 80%, a significance level of 5%, and an outcome proportion in each group of 69%, resulting in 118 patients in each group. We estimated at 10% of losses, resulting in a sample of 130 patients in each group.

Conclusion

The non-inferiority of NHT in relation to NCT will provide further evidence that replacing NCT with NHT is safe and effective in eligible patients, which is particularly relevant for populations with limited access to health services and for institutions with few available resources.

Neoadjuvant endocrine therapy for strongly hormone receptor-positive and HER2-negative early breast cancer: results of a prospective multi-center study

PURPOSE

For estrogen receptor (ER)-positive breast cancer, neoadjuvant endocrine therapy (NET) has been shown to be as effective as neoadjuvant chemotherapy (NACT). We evaluated the prognostic significance of Preoperative Endocrine Prognostic Index (PEPI).

METHODS

We conducted a prospective, multi-center, non-randomized, controlled trial that enrolled postmenopausal early-stage strongly ER-positive (≥ 50%) and HER2-negative breast cancer patients. All patients were given 4-month NET before surgery. The primary objective was to investigate the 5-year recurrence-free survival (RFS) in patients who had PEPI 0-1 or pathological complete response (pCR) without chemotherapy. Patients who had PEPI 0-1 or pCR were recommended to receive adjuvant endocrine therapy only and patients had PEPI ≥ 2 may receive adjuvant chemotherapy at the discretion of the treating physician.

RESULTS

A total of 410 patients were included and 352 patients constituted the per-protocol population. Overall, 9 patients (2.5%) had pCR (ypT0/is ypN0), 128 patients (36.4%) had PEPI = 0, and 56 patients (15.9%) had PEPI = 1. After a median follow-up of 60 months (4-104 months), patients who had PEPI 0-1 or pCR showed an improved 5-year RFS [99.5% (95% CI 98.5-99.9%) for PEPI 0-1 or pCR group vs. 93.7% (95% CI 89.6-97.8%) for PEPI ≥ 2 group, P = 0.028]. No survival difference was detected between patients received adjuvant chemotherapy vs. no chemotherapy among PEPI ≥ 2 cases.

CONCLUSION

PEPI 0-1 or pCR may be used to define a group of ER-positive and HER2-negative postmenopausal early breast cancer patients with low relapse risk for whom adjuvant chemotherapy can be safely withheld. Studies on the identification and alternative treatment options for endocrine-resistant tumors are warranted.

CLINICAL TRIAL REGISTRATION

NCT01613560.

Evaluation of Pharmacokinetics and Safety With Bioequivalence of Anastrozole in Healthy Chinese Volunteers: Bioequivalence Study Findings

Anastrozole is a third-generation aromatase inhibitor that exerts potent anti-breast cancer effects. This trial aimed to explore the pharmacokinetics (PK) and safety with bioequivalence of orally administered anastrozole provided by 2 sponsors in healthy volunteers.Two separate open-label, randomized, single-dose, crossover-design studies consisting of a fasting study (n = 23) and a fed study (n = 23, 1 participant withdrew before taking medication) were conducted. In each study, healthy volunteers were randomized to receive the test product (Haizheng Pharmaceutical Group) followed by the reference drug (AstraZeneca Pharmaceuticals LP), or vice versa. Each study subject received a 1-mg anastrozole tablet with a 21-day washout. The plasma concentrations of anastrozole were measured with liquid chromatography-tandem mass spectrometry, and PK parameters were determined by noncompartmental analysis. Forty-six healthy female volunteers were enrolled. For patients enrolled in the fasting study, the mean age was 55.0 years, mean weight was 57.1 kg, mean body mass index was 23.6 kg/m² , and mean height was 155.5 cm. For patients enrolled in the fed study, the mean age was 54.2 years, mean weight was 55.9 kg, mean body mass index was 23.9 kg/m² _, and mean height was 152.8 cm. All PK end points met the predefined criteria for PK equivalence. In fasting subjects, the median maximum plasma concentration was 23.4 and 22.6 at 1 hour for test and reference formulations, respectively. The maximum plasma concentration in fed subjects was 18.7 and 18.5 at 4 hours for test and reference formulations, respectively. Both fasting and fed studies achieved plausible bioequivalence. Anastrozole was well tolerated and exhibited a favorable safety profile at the prescribed doses. The severity of observed adverse events assessed according to the Common Terminology Criteria for Adverse Events (version CTCAE4.03) was mild, and some of the adverse events were not caused by anastrozole. Furthermore, the results of our study under fasting and fed conditions demonstrated bioequivalence of the test and reference products.

The Clinical Impact of Neoadjuvant Endocrine Treatment on Luminal-like Breast Cancers and Its Prognostic Significance: Results from a Single-Institution Prospective Cohort Study

Purpose: Neoadjuvant endocrine treatment (NET) has become a useful tool for the downstaging of luminal-like breast cancers in postmenopausal patients. It enables us to increase breast- conserving surgery (BCS) rates, provides an opportunity for us to assess in vivo NET effectiveness, and allows us to study any biological changes that may act as valid biomarkers. The purpose of this study was to evaluate the safety and effectiveness of NET, and to assess the role of Ki67 proliferation rate changes as an indicator of endocrine responsiveness. Methods: From 2016 to 2020, a single-institution cohort of patients, treated with NET and further surgery, was evaluated. In patients with Ki67 ≥ 10%, a second core biopsy was performed after four weeks. Information regarding histopathological and clinical changes was gathered. Results: A total of 115 estrogen receptor-positive (ER+)/HER2-negative patients were included. The median treatment duration was 5.0 months (IQR: 2.0−6.0). The median maximum size in the surgical sample was 40% smaller than the pretreatment size measured by ultrasound (p < 0.0001). The median pretreatment Ki67 expression was 20.0% (IQR: 12.0−30.0), and was reduced to 5.0% (IQR: 1.8−10.0) after four weeks, and to 2.0% (IQR: 1.0−8.0) in the surgical sample (p < 0.0001). BCS was performed on 98 patients (85.2%). No pathological complete responses were recorded. A larger Ki67 fold change after four weeks was significantly related to a PEPI score of zero (p < 0.002). No differences were observed between luminal A- and B-like tumors, with regard to fold change and PEPI score. Conclusions: In our cohort, NET was proven to be effective for tumor size and Ki67 downstaging. This resulted in a higher rate of conservative surgery, aided in therapeutic decision making, provided prognostic information, and constituted a safe and well-tolerated approach.

Cyclin-dependent kinase 4 and 6 inhibitors in combination with neoadjuvant endocrine therapy in estrogen receptor-positive early breast cancer: a systematic review and meta-analysis

The combination of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors and endocrine treatment has benefited patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER + /HER2-) metastatic breast cancer; however, its effects in the neoadjuvant setting for ER + /HER2- early breast cancer (EBC) are unclear. Systematic searches were performed in PubMed, Embase, Cochrane Library, and major oncological meetings for trials of CDK4/6 inhibitors plus neoadjuvant endocrine treatment (NET) vs. NET/neoadjuvant chemotherapy (NACT) alone up to January 30, 2021. We assessed the efficacy of CDK4/6 inhibitors plus NET vs. NET/NACT alone in ER + /HER2- EBC. Six studies that included 803 patients treated with CDK4/6 inhibitors plus NET vs. NET/NACT alone were used. Compared with NET/NACT alone, CDK4/6 inhibitors plus NET increased the complete cell cycle arrest (CCCA) rate (OR, 9.00; 95% CI, 5.42-14.96; P < 0.001). Nonsignificant differences between CDK4/6 inhibitors and NET/NACT alone occurred in the preoperative endocrine prognostic index (PEPI)-0 rate (OR, 1.13; 95% CI, 0.59-2.18; P = 0.71), pathological complete response (pCR) rate (OR, 0.75; 95% CI, 0.13-4.29; P = 0.74), objective response rate (ORR) (OR, 0.70; 95% CI, 0.21-2.29; P = 0.55), and disease control rate (DCR) (OR, 1.16; 95% CI, 0.47-2.89; P = 0.74). CDK4/6 inhibitors plus NET indicated a high risk of neutropenia (OR, 56.43; 95% CI, 15.76-202.11; P < 0.001) as an adverse effect (AE) and elevated alanine aminotransferase (ALT) level (OR, 15.30; 95% CI, 2.02-115.98; P = 0.008) as grade 3/4 AEs. Compared with NET/NACT alone, CDK4/6 inhibitors plus NET increased CCCA rate in ER + /HER2- EBC patients. CDK4/6 inhibitors plus NET did not substantially improve the PEPI-0 rate, pCR rate, ORR, or DCR. The combination increased the risk of neutropenia and elevated ALT levels. In the neoadjuvant setting, addition of CDK4/6 inhibitors to NET may be an option for treating ER + /HER2- EBC.

The Present and Future of Neoadjuvant Endocrine Therapy for Breast Cancer Treatment

Simple Summary

The treatment of breast cancer has evolved considerably over the last two decades, leading toward individualized disease management. Hormone-sensitive breast cancers constitute the vast majority of cases and endocrine therapy is the mainstay of their treatment. On the other hand, neoadjuvant or pre-surgical treatments provide a number of advantages for tumor management. In this review we will discuss the existing evidence on neoadjuvant endocrine therapy, as well as its possible future indications.

Abstract

Endocrine therapy (ET) has established itself as an efficacious treatment for estrogen receptor-positive (ER+) breast cancers, with a reduction in recurrence rates and increased survival rates. The pre-surgical approach with chemotherapy (NCT) has become a common form of management for large, locally advanced, or high-risk tumors. However, a good response to NCT is not usually expected in ER+ tumors. Good results with primary ET, mainly in elderly women, have encouraged studies in other stages of life, and nowadays neoadjuvant endocrine treatment (NET) has become a useful approach to many ER+ breast cancers. The aim of this review is to provide an update on the current state of art regarding the present and the future role of NET.

Mismatch repair deficiency predicts response to HER2 blockade in HER2-negative breast cancer

Resistance to endocrine treatment occurs in ~30% of ER+ breast cancer patients resulting in ~40,000 deaths/year in the USA. Preclinical studies strongly implicate activation of growth factor receptor, HER2 in endocrine treatment resistance. However, clinical trials of pan-HER inhibitors in ER+/HER2- patients have disappointed, likely due to a lack of predictive biomarkers. Here we demonstrate that loss of mismatch repair activates HER2 after endocrine treatment in ER+/HER2- breast cancer cells by protecting HER2 from protein trafficking. Additionally, HER2 activation is indispensable for endocrine treatment resistance in MutL- cells. Consequently, inhibiting HER2 restores sensitivity to endocrine treatment. Patient data from multiple clinical datasets supports an association between MutL loss, HER2 upregulation, and sensitivity to HER inhibitors in ER+/HER2- patients. These results provide strong rationale for MutL loss as a first-in-class predictive marker of sensitivity to combinatorial treatment with endocrine intervention and HER inhibitors in endocrine treatment-resistant ER+/HER2- breast cancer patients.

Neoadjuvant endocrine therapy for luminal breast cancer treatment: a first-choice alternative in times of crisis such as the COVID-19 pandemic

The epidemiological emergency caused by CoV-2 (COVID-19) has changed priorities in breast cancer management. In those places where the pandemic has had the greatest effect, it is of paramount importance for most patients to be at home, reducing or postponing their attendance at clinics, as well as avoiding surgeries. In this scenario, neoadjuvant endocrine treatment could be an appropriate alternative treatment for hormone receptor positive breast cancer (luminal-like tumours) in order to minimise hospital admissions and to delay elective surgeries. Accordingly, we present a simple protocol that can be applied to most cases of luminal-like breast cancer and is appropriate for the majority of secondary or tertiary medical centres, or even primary care.

Utility of Ki67 labeling index, cyclin D1 expression, and ER-activity level in postmenopausal ER-positive and HER2-negative breast cancer with neoadjuvant chemo-endocrine therapy

In this study, we investigated the relationships of pathological response after neoadjuvant chemo-endocrine therapy with alterations in the Ki67 labeling index (LI), expression of cyclin D1 (CCND1) and progesterone receptor (PgR), and estrogen receptor (ER) activity in breast cancer. A total of 43 Japanese post-menopausal ER-positive and human epidermal growth factor receptor 2-negative invasive breast cancer patients with tumors >2 cm or positive lymph nodes were enrolled. Exemestane alone was administered for 2 months. Neoadjuvant chemo-endocrine therapy included four cycles of doxorubicin plus paclitaxel followed by weekly paclitaxel. The immunohistochemical expression of Ki67 LI, CCND1, and PgR, and ER activity were evaluated using core needle biopsy samples at the pretreatment and post-exemestane alone stages. ER activity was evaluated through transfection of an adenovirus vector carrying an estrogen-response element-green fluorescent protein gene. In current study, marked pathological responses (including 4.7% with pathological complete response) were obtained in 34.9% of patients. Ki67 LI and PgR expression were significantly decreased after treatment. High Ki67 LI at pretreatment was a significant predictive factor of marked pathological response. At the stage of post-exemestane alone, Ki67 LI was not significantly associated with pathological response; however, high CCND1 expression was significantly correlated with high Ki67 LI. Moreover, low-level ER activity at the post-exemestane alone stage was significantly associated with marked pathological response. In conclusions, pretreatment Ki67 LI was a predictor of response to neoadjuvant chemo-endocrine therapy. CCND1 expression and ER activity at the post-endocrine therapy alone stage may be useful in determining further treatments.

Network-guided prediction of aromatase inhibitor response in breast cancer

Prediction of response to specific cancer treatments is complicated by significant heterogeneity between tumors in terms of mutational profiles, gene expression, and clinical measures. Here we focus on the response of Estrogen Receptor (ER)+ post-menopausal breast cancer tumors to aromatase inhibitors (AI). We use a network smoothing algorithm to learn novel features that integrate several types of high throughput data and new cell line experiments. These features greatly improve the ability to predict response to AI when compared to prior methods. For a subset of the patients, for which we obtained more detailed clinical information, we can further predict response to a specific AI drug.

Breast cancer is the second most common type of cancer in women, with an incidence rate of over 250,000 cases per year, and breast cancer cases show significant heterogeneity in clinical and omic measures. Estrogen receptor positive (ER+) tumors typically grow in response to estrogen, and in post menopausal women, estrogen is only produced in peripheral tissues via the aromatase enzyme. Inhibition of aromatase is often an effective treatment for ER+ tumors, but aromatase inhibitor therapy is not effective for all tumors, and causes of this heterogeneity in response are largely not known. In this work, we present a feature construction and classification method to predict response to aromatase inhibitor therapy. We use network smoothing techniques to combine tumor omic data into predictive features, which we use as input to standard machine learning algorithms. We train predictive models using clinical data, including high-quality clinical data from UPMC patients, and show that our method outperforms previous approaches in predicting response to aromatase inhibitor therapy.

Effects of psoralen on the pharmacokinetics of anastrozole in rats

CONTEXT

Psoralen and anastrozole are always used together for breast cancer patients in Chinese clinics.

OBJECTIVE

This study investigates the effects of psoralen on the pharmacokinetics of anastrozole in rats and its potential mechanism.

MATERIALS AND METHODS

The pharmacokinetics of orally administered anastrozole (0.5 mg/kg) with (test group) or without (Control group) psoralen pretreatment (20 mg/kg/day for 10 days) in male Sprague-Dawley rats (six rats in each group) were investigated. The plasma concentration of anastrozole was determined using a sensitive and reliable LC-MS/MS method. Additionally, the effects of psoralen on the intestine transport and metabolic stability of anastrozole (1 μM) were investigated using a Caco-2 cell transwell model and rat liver microsome incubation systems.

RESULTS

The results indicated that psoralen could significantly increase the C_max (from 56.74 ± 3.17 ng/mL to 83.26 ± 6.87 ng/mL), and t_1/2 (from 10.80 ± 1.05 to 14.29 ± 1.38 h) of anastrozole (p < 0.05). Psoralen could also significantly decrease the efflux ratio of anastrozole from 1.88 to 1.32 (p < 0.05). Additionally, the intrinsic clearance rates of anastrozole decreased significantly (from 62.83 to 43.97 μL/min/mg protein) (p < 0.05) with psoralen pretreatment in rat liver microsome incubation systems.

DISCUSSION AND CONCLUSIONS

This study indicates that when the rats were pretreated with psoralen, the system exposure of anastrozole would be increased significantly. The results showed that the herb-drug interaction between psoralen and anastrozole might occur when they were co-administered, and future studies in humans also need to investigate its herb-drug interaction potential.

Predictive markers of endocrine response in breast cancer

Ongoing clinical and research efforts seek to optimise the use of endocrine therapy in the treatment of breast cancer. Accurate biomarkers are needed that predict response for individual patients. The presence of the estrogen receptor (ER) as the direct (for tamoxifen and fulvestrant) or indirect (for aromatase inhibitors) target molecule for endocrine therapy remains the foremost biomarker and determinant of response. However, ER expression only poorly predicts outcome and further indicators of response or resistance are required. The development and application of molecular signature assays such as Oncotype Dx, Prosigna, Mammaprint and Endopredict have provided valuable information on prognosis and these are being used to support clinical decision making on whether endocrine therapy alone alongside surgery is sufficient for ER-positive early stage breast cancers or whether combination of endocrine with chemotherapy are also warranted. Ki67, the proliferation marker, has been widely used in the neo-adjuvant (pre-operative) setting to help predict response and long term outcome. Gene expression studies within the same setting have allowed monitoring of changes of potential predictive markers. These have identified frequent changes in estrogen-regulated and proliferation genes. Specific molecules such as mutant ER may also prove helpful biomarkers in predicting outcome and monitoring response to treatment.

Neoadjuvant Endocrine Therapy in Breast Cancer Upregulates the Cytotoxic Drug Pump ABCG2/BCRP, and May Lead to Resistance to Subsequent Chemotherapy

INTRODUCTION

Neoadjuvant treatments for primary breast cancer are becoming more common; however, little is known about how these impact on response to subsequent adjuvant therapies. Conveniently, neoadjuvant therapy provides opportunities to consider this question, by studying therapy-induced expression changes using comparisons between pre- and posttreatment samples. These data are relatively lacking in the context of neoadjuvant endocrine therapy, as opposed to the more common neoadjuvant chemotherapy. Here, we investigate the relevance of expression of the xenobiotic transporter ABCG2/BCRP, a gene/protein associated with chemoresistance, in the context of neoadjuvant endocrine therapy and particularly with reference to subsequent chemotherapy treatment.

MATERIALS AND METHODS

ABCG2/BCRP expression was assessed by immunohistochemistry or by expression arrays in matched patient samples pre- and post-neoadjuvant endocrine therapy. Cell culture was used to model the impact of endocrine therapy-induced changes in ABCG2/BCRP on subsequent chemotherapy response, using Western blots, quantitative polymerase chain reaction, survival assays, and cell cycle analyses.

RESULTS

ABCG2/BCRP was commonly and significantly upregulated in breast cancers after treatment with neoadjuvant endocrine therapy in 3 separate cohorts encompassing a total of 200 patients. Treatment with the endocrine therapeutic tamoxifen similarly induced ABCG2/BCRP upregulation in a relevant model cell line, the estrogen receptor-positive line T47D. Critically, this upregulation was associated with significantly increased chemoresistance to subsequent treatment with epirubicin, an anthracycline commonly used in breast cancer adjuvant chemotherapy.

CONCLUSION

Our data suggest that neoadjuvant endocrine therapy may induce poor responses to adjuvant chemotherapy, and therefore, that clinical outcomes following this treatment sequence warrant further study.

Perspective on the interpretation of research and translation to clinical care with therapy-associated metastatic breast cancer progression as an example

This commentary was written as a collaboration between the Board of the Metastasis Research Society and two patients with metastatic breast cancer. It was conceived in response to how preclinical scientific research is sometimes presented to non-scientists in a way that can cause stress and confusion. Translation of preclinical findings to the clinic requires overcoming multiple barriers. This is irrespective of whether the findings relate to exciting responses to new therapies or problematic effects of currently used therapies. It is important that these barriers are understood and acknowledged when research findings are summarized for mainstream reporting. To minimize confusion, patients should continue to rely on their oncology care team to help them interpret whether research findings presented in mainstream media have relevance for their individual care. Researchers, both bench and clinical, should work together where possible to increase options for patients with metastatic disease, which is still in desperate need of effective therapeutic approaches.

Protein biomarkers for subtyping breast cancer and implications for future research

INTRODUCTION

Breast cancer subtypes are currently defined by a combination of morphologic, genomic, and proteomic characteristics. These subtypes provide a molecular portrait of the tumor that aids diagnosis, prognosis, and treatment escalation/de-escalation options. Gene expression signatures describing intrinsic breast cancer subtypes for predicting risk of recurrence have been rapidly adopted in the clinic. Despite the use of subtype classifications, many patients develop drug resistance, breast cancer recurrence, or therapy failure. Areas covered: This review provides a summary of immunohistochemistry, reverse phase protein array, mass spectrometry, and integrative studies that are revealing differences in biological functions within and between breast cancer subtypes. We conclude with a discussion of rigor and reproducibility for proteomic-based biomarker discovery. Expert commentary: Innovations in proteomics, including implementation of assay guidelines and standards, are facilitating refinement of breast cancer subtypes. Proteomic and phosphoproteomic information distinguish biologically functional subtypes, are predictive of recurrence, and indicate likelihood of drug resistance. Actionable, activated signal transduction pathways can now be quantified and characterized. Proteomic biomarker validation in large, well-designed studies should become a public health priority to capitalize on the wealth of information gleaned from the proteome.