Fulvestrant 500 mg Versus Anastrozole 1 mg for the First-Line Treatment of Advanced Breast Cancer: Overall Survival Analysis From the Phase II FIRST Study

First‑line endocrine therapy for hormone receptor positive and HER‑2 negative metastatic breast cancer: A Bayesian network meta‑analysis

Endocrine therapy has become the fundamental treatment option for hormone receptor-positive (HR+) and receptor tyrosine-protein kinase erbB-2-negative (HER2-) metastatic breast cancer (mBC). While treatments incorporating cyclin-dependent kinase (CDK)4 and 6 inhibitors are more prevalent than ever, comparisons among those regimens are scarce. The aim of the present study was to identify the most effective maintenance treatment for patients with HR+ and HER2- mBC. To this end, databases including PubMed, Embase, Cochrane Library, Scopus and Google Scholar were searched from inception to August, 2023. The endpoints comprised overall survival (OS) and progression free survival (PFS). For dichotomous variants, hazard ratios (HRs) and odds ratios (ORs) were generated, while standard mean difference (SMD) was used for consecutive variants by Bayesian network meta-analysis to make pairwise comparisons among regimens, to determine the optimal therapy. These processes were conducted using Rstudio 4.2.2 orchestrated with STATA 17.0 MP. A total of 16 randomized controlled trials including 7,174 patients with 11 interventions were analyzed. Compared with aromatase inhibitor (AI), palbociclib plus AI (PalboAI) exhibited a significantly longer PFS up to the 36th month of follow-up [HR=1.7; 95% credible interval, 1.36-2.16], including on the 3rd [OR=2.22; 95% confidence interval (CI), 1.10-4.47], 6th (OR=2.39; 95% CI, 1.21-4.69), 12th (OR=1.94; 95% CI, 1.34-2.79), 18th (OR=2.38; 95% CI, 1.65-3.44), 24th (OR=2.39; 95% CI, 1.67-3.43), 30th (OR=2.10; 95% CI, 1.62-2.74) and 36th (OR=2.66; 95% CI, 1.37-5.18) month of follow-up. Additionally, abemaciclib plus fulvestrant exhibited significant effects compared with AI alone between 12 and 36 months. Ribociclib plus fulvestrant, ribociclib plus AI and dalpiciclib plus AI exerted significant effects compared with AI alone between 12 and 30 months. Considering the effect on OS and PFS together with adverse reactions, safety, medical compliance and route of administration, PalboAI was found to be the optimal treatment for HR+/HER2-mBC. However, additional head-to-head clinical trials are warranted to confirm these findings.

The impact of previous therapy on overall-survival in registration clinical trials for 1st line metastatic breast cancer a systemic review

AIM

To explore the impact of previous treatment on the efficacy of investigational new drugs in registration trials for 1st line metastatic breast cancer (MBC).

METHODS

Thirteen US Food and Drug Administration (FDA) approved indications for 1st line MBC between 1/2000-12/2023 were identified and their supporting publications were searched in the ClinicalTrials.gov and Google Scholar. Where available, hazard ratios (HRs) and 95 % confidence intervals (CI) for overall-survival (OS) were pooled into meta-analysis and the difference in the magnitude of OS benefit between treatment naïve and previously treated patients was analyzed.

RESULTS

There was no difference in the magnitude of OS benefit between treatment-naïve and previously treated patients (HR=0.72 versus 0.80,p for difference=0.25). In indications for triple-negative BC, treatment-naïve patients had higher magnitude of OS benefit compared to previously treated patients (HR=0.53 versus 0.81,p=0.03). In indications for luminal disease, the magnitude of benefit was comparable between the subgroups.

CONCLUSIONS

In trials supporting 1st line therapy for TNBC the magnitude of benefit is significantly higher in treatment naïve compared to previously treated patients. Our findings may represent a previously unrecognized bias, potentially over-estimating the benefit of triple-negative BC new drugs.

Recent progress of CDK4/6 inhibitors' current practice in breast cancer

Dysregulated cellular proliferation represents a hallmark feature across all cancers. Aberrant activation of the cyclin-dependent kinase 4 and 6 (CDK4/6) pathway, independent of mitogenic signaling, engenders uncontrolled breast cancer cell proliferation. Consequently, the advent of CDK4/6 inhibition has constituted a pivotal milestone in the realm of targeted breast cancer therapy. The combination of CDK4/6 inhibitors (CDK4/6i) with endocrine therapy (ET) has emerged as the foremost therapeutic modality for patients afflicted with hormone receptor-positive (HR + )/HER2-negative (HER2-) advanced breast cancer. At present, the Food and Drug Administration (FDA) has sanctioned various CDK4/6i for employment as the primary treatment regimen in HR + /HER2- breast cancer. This therapeutic approach has demonstrated a substantial extension of progression-free survival (PFS), often amounting to several months, when administered alongside endocrine therapy. Within this comprehensive review, we systematically evaluate the utilization strategies of CDK4/6i across various subpopulations of breast cancer and explore potential therapeutic avenues following disease progression during application of CDK4/6i therapy.

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

AIM

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

RESULTS

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

CONCLUSION

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

Next generation selective estrogen receptor degraders in postmenopausal women with advanced-stage hormone receptors-positive, HER2-negative breast cancer

Breast cancer is the most prevalent malignancy in women, and is characterized by its heterogeneity; exhibiting various subgroups identifiable through molecular biomarkers that also serve as predictive indicators. More than two thirds of breast tumors are classified as luminal with positive hormone receptors (HR), indicating that cancer cells proliferation is promoted by hormones. Endocrine therapies play a vital role in the effective treatment of breast cancer by manipulating the signaling of estrogen receptors (ER), leading to a reduction in cell proliferation and growth rate. Selective estrogen receptor modulators (SERMs), such as tamoxifen and toremifene, function by blocking estrogen's effects. Aromatase inhibitors (AI), including anastrozole, letrozole and exemestane, suppress estrogen production. On the other hand, selective estrogen receptor degraders (SERDs), like fulvestrant, act by blocking and damaging estrogen receptors. Tamoxifen and AI are widely used both in early- and advanced-stage disease, while fulvestrant is used as a single agent or in combination with other agents like the cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors (palbociclib, abemaciclib, ribociclib) or alpelisib for advanced-stage disease. Currently, SERDs are recognized as an effective therapeutic approach for the treatment of ER-positive breast cancer, showing proficiency in reducing and blocking ER signaling. This review aims to outline the ongoing development of novel oral SERDs from a practical therapeutic perspective, enhancing our understanding of the mechanisms of action underlying these compounds.

Abemaciclib plus endocrine therapy versus chemotherapy after progression on prior palbociclib in HR+/HER2- metastatic breast cancer: A single center real-world study in China

BACKGROUND

Cyclin-dependent kinase (CDK) 4/6 inhibitor plus endocrine therapy (ET) become standard-of-care for patients with hormone receptor-positive, human epidermal growth factor receptor-2 negative (HR+/HER2-) metastatic breast cancer (MBC). However, the optimal therapeutic paradigm after progression on CDK4/6 inhibitor remains unclear. This study aimed to evaluate the efficacy and safety of abemaciclib with switching ET versus chemotherapy after progression on prior palbociclib-based ET in Chinese patients with HR+/HER2- MBC.

METHODS

From 414 consecutive patients with HR+/HER2- MBC who had been treated with palbociclib plus ET from September 2018 to May 2022 in Peking University Cancer Hospital, we identified 80 patients who received abemaciclib plus switching ET or chemotherapy after progression on palbociclib, matched for age, original stage at diagnosis, disease-free interval, and tumor burden at 1:1 ratio. The primary endpoint was progression-free survival (PFS) compared using the Kaplan-Meier method. A Cox proportional hazard model was performed to identify clinical factors associated with PFS in the abemaciclib group.

RESULTS

The median PFS was 6.0 months (95% confidence interval [CI]: 3.94-8.06) in abemaciclib group and 4.0 months (95% CI, 2.52-5.49) in chemotherapy group (p = 0.667). And, there was no difference in median PFS between the sequential and nonsequential arm (6.0 vs. 6.0 months) in the abemaciclib group though fewer lines of prior systemic therapy and longer PFS from prior palbociclib in the sequential arm. However, patients with prior palbociclib as the first-line therapy had a significantly longer median PFS versus prior palbociclib as ≥2nd-line therapy (11.0 vs. 5.0 months, p = 0.043). Based on multivariable analysis, ER+/PR+ was an independent factor associated with longer PFS. There was no significant difference in overall survival between the abemaciclib and chemotherapy groups (p = 0.069).

CONCLUSION

Our findings indicate that abemaciclib plus switching ET might be one of feasible treatment options for Chinese patients with HR+/HER2- MBC after progression on prior palbociclib-based therapy in addition to chemotherapy.

Influence of tumor microenvironment on the different breast cancer subtypes and applied therapies

Despite the significant improvements made in breast cancer therapy during the last decades, this disease still has increasing incidence and mortality rates. Different targets involved in general processes, like cell proliferation and survival, have become alternative therapeutic options for this disease, with some of them already used in clinic, like the CDK4/6 inhibitors for luminal A tumors treatment. Nevertheless, there is a demand for novel therapeutic strategies focused not only on tumor cells, but also on their microenvironment. Tumor microenvironment (TME) is a very complex and dynamic system that, more than surrounding and supporting tumor cells, actively participates in tumor development and progression. During the last decades, it has become clear that the cellular and acellular components of TME differ between the various breast cancer subtypes and shape the differences regarding their severity and prognosis. The pivotal role of the TME in controlling tumor growth and influencing responses to therapy represents a potential source for novel targets and therapeutic strategies. In this review, we present a description of the multiple therapeutic options used for different breast cancer subtypes, as well as the influence that the TME may exert on the development of the disease and on the response to the distinct therapies, which in some cases may explain their failure by the occurrence of relapses and resistance. Furthermore, the ongoing studies focused on the use of TME components for developing potential cancer treatments are described.

Oral SERD, a Novel Endocrine Therapy for Estrogen Receptor-Positive Breast Cancer

Breast cancer is the most common cancer among women worldwide, and estrogen receptor-positive (ER+) breast cancer accounts for a significant proportion of cases. While various treatments are available, endocrine therapies are often the first-line treatment for this type of breast cancer. However, the development of drug resistance poses a significant challenge in managing this disease. ESR1 mutations have been identified as a common mechanism of endocrine therapy resistance in ER+ breast cancer. The first-generation selective estrogen receptor degrader (SERD) fulvestrant has shown some activity against ESR1 mutant tumors. However, due to its poor bioavailability and need for intramuscular injection, it may not be the optimal therapy for patients. Second-generation SERDs were developed to overcome these limitations. These newer drugs have improved oral bioavailability and pharmacokinetics, making them more convenient and effective for patients. Several oral SERDs are now in phase III trials for early and advanced ER+ breast cancer. This review summarizes the background of oral SERD development, the current status, and future perspectives.

Fulvestrant with or without anti-HER2 therapy in patients in a postmenopausal hormonal state and with ER-positive HER2-positive advanced or metastatic breast cancer: A subgroup analysis of data from the Safari study (JBCRG-C06)

BACKGROUND

The role of endocrine therapy in the treatment of patients in a postmenopausal hormonal state and with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-positive advanced or metastatic breast cancer (AMBC) is unclear.

METHODS

We analyzed the data from 94 patients with ER-positive HER2-positive AMBC enrolled in the Safari study (UMIN000015168), a retrospective cohort study of 1072 ER-positive AMBC patients in a postmenopausal hormonal state who received fulvestrant 500 mg (F500): (1) to compare time to treatment failure (TTF) and overall survival (OS) by treatment group, and TTF by treatment line; (2) in patients who received endocrine therapy (including F500) or anti-HER2 therapy as initial systemic therapy before chemotherapy, to investigate relations between TTF for the first-line therapy or time to chemotherapy (TTC) and OS; (3) to investigate factors associated with OS.

RESULTS

The TTF was longer in the patients treated with F500 as first- or second-line therapy (n = 20) than in those who received later-line F500 therapy (n = 74) (6.6 vs. 3.7 months; HR, 1.98; p = 0.014). In the 59 patients who received endocrine therapy or anti-HER2 therapy as initial systemic therapy before chemotherapy, those with TTC ≥3 years had longer median OS than those with TTC <3 years (10.5 vs. 5.9 years; HR, 0.32; p = 0.001). Longer TTC was associated with prolonged OS.

CONCLUSIONS

In patients with ER-positive HER2-positive AMBC enrolled in the Safari study, TTF was longer in patients who received F500 as first- or second-line therapy. In patients who received chemotherapy-free initial systemic therapy, the prolonged OS in those with TTC ≥3 years suggests that this value may be a helpful cut-off for indicating clinical outcomes.

Systemic therapy for hormone receptor-positive/human epidermal growth factor receptor 2-negative early stage and metastatic breast cancer

Hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer is defined by the presence of the estrogen receptor and/or the progesterone receptor and the absence of HER2 gene amplification. HR-positive/HER2-negative breast cancer accounts for 65%-70% of all breast cancers, and incidence increases with increasing age. Treatment varies by stage, and endocrine therapy is the mainstay of treatment in both early stage and late-stage disease. Combinations with cyclin-dependent kinase 4/6 inhibitors have reduced distant recurrence in the early stage setting and improved overall survival in the metastatic setting. Chemotherapy is used based on stage and tumor biology in the early stage setting and after endocrine resistance for advanced disease. New therapies, including novel endocrine agents and antibody-drug conjugates, are now changing the treatment landscape. With the availability of new treatment options, it is important to define the optimal sequence of treatment to maximize clinical benefit while minimizing toxicity. In this review, the authors first discuss the pathologic and molecular features of HR-positive/HER2-negative breast cancer and mechanisms of endocrine resistance. Then, they discuss current and emerging therapies for both early stage and metastatic HR-positive/HER2-negative breast cancer, including treatment algorithms based on current data.

Nanoparticle-Based Combination Therapy Enhances Fulvestrant Efficacy and Overcomes Tumor Resistance in ER-Positive Breast Cancer

Nanoparticles (NP) spanning diverse materials and properties have the potential to encapsulate and to protect a wide range of therapeutic cargos to increase bioavailability, to prevent undesired degradation, and to mitigate toxicity. Fulvestrant, a selective estrogen receptor degrader, is commonly used for treating patients with estrogen receptor (ER)-positive breast cancer, but its broad and continual application is limited by poor solubility, invasive muscle administration, and drug resistance. Here, we developed an active targeting motif-modified, intravenously injectable, hydrophilic NP that encapsulates fulvestrant to facilitate its delivery via the bloodstream to tumors, improving bioavailability and systemic tolerability. In addition, the NP was coloaded with abemaciclib, an inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6), to prevent the development of drug resistance associated with long-term fulvestrant treatment. Targeting peptide modifications on the NP surface assisted in the site-specific release of the drugs to ensure specific toxicity in the tumor tissues and to spare normal tissue. The NP formulation (PPFA-cRGD) exhibited efficient tumor cell killing in both in vitro organoid models and in vivo orthotopic ER-positive breast cancer models without apparent adverse effects, as verified in mouse and Bama miniature pig models. This NP-based therapeutic provides an opportunity for continual and extensive clinical application of fulvestrant, thus indicating its promise as a treatment option for patients with ER-positive breast cancer.

SIGNIFICANCE

A smart nanomedicine encapsulating fulvestrant to improve its half-life, bioavailability, and tumor-targeting and coloaded with CDK4/6 inhibitor abemaciclib to block resistance is a safe and effective therapy for ER-positive breast cancer.

Retrospective Evaluation of Fulvestrant Efficacy and Clinical Results in Patients Using Fulvestrant

AIM

Fulvestrant is a drug used in the treatment of metastatic hormone receptor-positive breast cancer (mHRPBC). Although clinical trials have shown the efficacy of fulvestrant, real-life data are limited and data from clinical trials and real-life settings sometimes may be seen differently. Therefore, we retrospectively reviewed mHRPBC patients followed in our center and taking fulvestrant to evaluate the efficacy and clinical outcomes of the drug and also to identify factors affecting the efficacy and clinical outcomes of fulvestrant.

MATERIALS AND METHODS

Patients who were followed up with the diagnosis of metastatic breast cancer between 2010 and 2022 and using fulvestrant were retrospectively analyzed.

RESULTS

The median progression-free survival (PFS) time was 9 [95% confidence interval (CI): 7.13-10.18] months and the median overall survival time was 28 (95% CI: 22.53-34.93) months. According to multivariate analyses, PFS was associated with age (p=0.041), body mass index (BMI) (p=0.043), brain metastasis (p=0.033), fulvestrant line (p=0.002), and use of pre-fulvestrant chemotherapy (p=0.032).

CONCLUSION

Fulvestrant is an effective drug in mHRPBC. Fulvestrant is more effective in patients whose BMI index is under 30, without brain metastases, without prior chemotherapy, under 65 years of age, and used fulvestrant in the early treatment line. The efficacy of fulvestrant may vary according to age and BMI.

New tamoxifen analogs for breast cancer therapy: synthesis, aromatase inhibition and in silico studies

A new class of tamoxifen analogues, using McMurry reaction conditions, is described. The scheme involved the conversion of ketoprofen (6) into amide derivatives 7 and 8, by coupling with N1,N1-substituted propan-1,3-diamine derivatives in the presence DIC and HOB. Treatment of 7 and 8 with various ketones under McMurry reaction conditions afforded the tamoxifen analogues 9-16. All the analogues were screened in vitro for their aromatase inhibitory and antiproliferative activity against MCF-7 breast cancer cells. Compounds 10, 11 and 12 showed a potent activity against MCF-7 cell lines breast cancer with IC50 values of 0.070, 0.042 and 0.077 µM of selectivity index (SI) 3.0, 2.5 and 2.6, respectively. Further, 12 exhibited potent activity against estrogen receptor (14.7 ± 2.4 nM), while compound 10 was the most active analogues against aromatase with IC50 of (0.070 nM). Furthermore, all new compounds were docked into human placental aromatase enzyme and estrogen receptor and showed very good correlations with experimental IC50. Therefore, we can consider these designed compounds as starting scaffold to design an efficient drug against estrogen receptor and aromatase.Communicated by Ramaswamy H. Sarma.

Shifting Treatment Paradigms: Improvements in HR-Positive, HER-2- Negative Breast Cancer Care in Poland from a Clinical Perspective

Patients with hormone-receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer constitute about 70% of the breast cancer population. About 35% of these patients develop distant metastases and their treatment will be palliative. Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors were shown to significantly improve the outcomes of these patients. In combination with endocrine therapy, they have become the standard first-line treatment for HR-positive, HER2-negative breast cancer. In Poland, treatment with CDK4/6 inhibitors is reimbursed only for patients participating in the drug program of the Ministry of Health. However, fulfilling the eligibility criteria for the program may be challenging both for patients and for clinicians. This may lead to a delay in treatment with CDK4/6 inhibitors or a decision to use older and less effective drugs that are more widely available. The aim of this review was to compare the efficacy of first-line therapies in patients with HR-positive, HER2-negative metastatic breast cancer depending on the use of CDK4/6 inhibitors. We compared the efficacy of previous standard therapies with that of ribociclib, a CDK4/6 inhibitor, based on the median progression-free survival (PFS) as an outcome. Median PFS is not affected by the efficacy of subsequent treatment lines and is easy to interpret both for clinicians and for patients. The first-line treatment with chemotherapy or endocrine therapy (without CDK4/6 inhibitors) prolongs median PFS by several months and even to over a dozen months. The first-line treatment with endocrine therapy plus CDK4/6 inhibitors provides an opportunity to achieve a median PFS of more than 25 months and to prolong it by about 9 to 14 months.

Risk of seizures in a population of women with BRCA-positive metastatic breast cancer from an electronic health record database in the United States

BACKGROUND

Incidence and risk factors for seizures among women with advanced breast cancer (BC) and brain metastases are not well characterized across treatment-related or clinical subtypes. This study leveraged a large real-world dataset to describe incidence and risk factors for seizures in BRCA-associated metastatic breast cancer.

METHODS

The Optum® de-identified electronic health records database was used. Females with a BC diagnoses between 2008 and 2018, with clinic visits 12 months before BC index date, evidence of BRCA mutation (BRCA+), evidence of metastasis, and no previous cancers were included. Analyses were stratified by the overall BRCA+ cohort and 4 molecular phenotypes: HER2+/HR- (human epidermal growth factor 2/hormone receptor), HER2-/HR+, HER2+/HR+, and triple negative BC (TNBC; HER2-/HR-). Seizures were identified using diagnosis codes and natural language processing. Incidence, occurrence rates, and cumulative incidence of seizures from the diagnosis of metastasis to the end of follow up were calculated. Comparisons were made between phenotypes and stratified on PARP inhibitor use, diagnosed brain metastases, history of seizures, and anticonvulsants use before BC. All comparisons included age at metastasis, number of prior lines of treatment, and metastasis location as covariates.

RESULTS

27.8% of 7941 BRCA+ patients had ≥1 seizure over a mean follow-up time of 2.35 years. Incidence and occurrence rates were 11.83 (95% CI: 11.35-12.33) and 201.3 (95% CI: 198.05-204.50), respectively, per 100 person-years. HER2-/HR+ and TNBC patients had the lowest and highest seizure incidence rates, respectively (10.94 [95% CI: 10.23-11.71] and 16.83 [95% CI: 15.34-18.46]). With HER2-/HR+ as the reference group in a competing risk analysis, TNBC (hazard ratio, HR = 1.35; 95%CI: 1.21, 1.52; p < 0.001) and HER2+/HR- (HR = 1.29; 95%CI: 1.07, 1.56; p < 0.01) patients had a greater risk of seizures. Patients with diagnosed brain metastases or a history of seizures had higher seizure rates. Incidence trended higher with PARP inhibitor use, but patient numbers were low.

CONCLUSIONS

This study provides novel real-world evidence on seizure incidence rates in BRCA+ BC patients, even those without diagnosed brain metastases, and underscores the need to understand patients' tumor phenotypes when assessing seizure risk. These findings may have implications for clinical practice and assessment of benefit-risk ratios of new therapeutic agents.

HR+/HER2- de novo metastatic breast cancer: a true peculiar entity?

De novo metastatic breast cancer (dnMBC) accounts for ~6-10% of all breast cancers and for ~30% of MBC with increasing incidence over time. Hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR⁺/HER2^-) tumours are the most frequent subtype with a similar incidence to that observed amongst recurrent MBC (rMBC). Higher frequency of PI3KCA and ARID2 mutations and a lower frequency of ESR1 mutations and of genes involved in DNA damage, as compared with rMBC, have been reported in HR⁺/HER2^- dnMBC; however, these are not correlating with prognosis, whilst tumour mutational burden is inversely correlated with outcome. Bone represents the most frequent metastatic site, being the single site in up to 60% of patients with dnMBC. HR⁺/HER2^- dnMBC has been generally reported to have better outcomes than rMBC, with a median overall survival ranging from 26 months to nearly 5 years in patients with favourable features such as age <40 years and bone-only disease, but not when compared with patients with late recurring disease (≥2-5 years). Analyses of the de novo cohorts within randomized clinical trials and large real-world series report a better outcome after treatment with CDK4/6 inhibitors and endocrine agents as compared to rMBC. Despite the limitations of retrospective studies and controversial results of the randomized trials, locoregional treatment of the primary tumour after response to systemic therapy appears to confer a survival benefit, particularly in patients with favourable prognostic factors. Altogether genomic, biological and clinical findings highlight HR⁺/HER2^- dnMBC as a peculiar entity as compared with rMBC and deserve a dedicated treatment algorithm. This article is part of the Tackling clinical complexity in breast cancer Special Issue: https://www.drugsincontext.com/special_issues/tackling-clinical-complexity-in-breast-cancer/.

The race to develop oral SERDs and other novel estrogen receptor inhibitors: recent clinical trial results and impact on treatment options

Hormonal therapy plays a vital part in the treatment of estrogen receptor-positive (ER +) breast cancer. ER can be activated in a ligand-dependent and independent manner. Currently available ER-targeting agents include selective estrogen receptor modulators (SERMs), selective estrogen receptor degraders (SERDs), and aromatase inhibitors (AIs). Estrogen receptor mutation (ESR1 mutation) is one of the common mechanisms by which breast cancer becomes resistant to additional therapies from SERMs or AIs. These tumors remain sensitive to SERDs such as fulvestrant. Fulvestrant is limited in clinical utilization by its intramuscular formulation and once-monthly injection in large volumes. Oral SERDs are being rapidly developed to replace fulvestrant with the potential of higher efficacy and lower toxicities. Elacestrant is the first oral SERD that went through a randomized phase III trial showing increased efficacy, especially in tumors bearing ESR1 mutation, and good tolerability. Two other oral SERDs recently failed to achieve the primary endpoints of longer progression-free survival (PFS). They targeted tumors previously treated with several lines of prior therapies untested for ESR1 mutation. Initial clinical trial data demonstrated that tumors without the ESR1 mutation are less likely to benefit from the SERDs and may still respond to SERMs or AIs, including tumors previously exposed to hormonal therapy. Testing for ESR1 mutation in ongoing clinical trials and in hormonal therapy for breast cancer is highly recommended. Novel protein degradation technologies such as proteolysis-targeting chimera (PROTACS), molecular glue degrader (MGD), and lysosome-targeting chimeras (LYTACS) may result in more efficient ER degradation, while ribonuclease-targeting chimeras (RIBOTAC) and small interfering RNA (siRNA) may inhibit the production of ER protein.

An overview on Estrogen receptors signaling and its ligands in breast cancer

Estrogen governs the regulations of various pathological and physiological actions throughout the body in both males and females. Generally, 17β-estradiol an endogenous estrogen is responsible for different health problems in pre and postmenopausal women. The major activities of endogenous estrogen are executed by nuclear estrogen receptors (ERs) ERα and ERβ while non-genomic cytoplasmic pathways also govern cell growth and apoptosis. Estrogen accomplished a fundamental role in the formation and progression of breast cancer. In this review, we have hyphenated different studies regarding ERs and a thorough and detailed study of estrogen receptors is presented. This review highlights different aspects of estrogens ranging from receptor types, their isoforms, structures, signaling pathways of ERα, ERβ and GPER along with their crystal structures, pathological roles of ER, ER ligands, and therapeutic strategies to overcome the resistance.

Serial monitoring of genomic alterations in circulating tumor cells of ER-positive/HER2-negative advanced breast cancer: feasibility of precision oncology biomarker detection

Nearly all estrogen receptor (ER)-positive (POS) metastatic breast cancers become refractory to endocrine (ET) and other therapies, leading to lethal disease presumably due to evolving genomic alterations. Timely monitoring of the molecular events associated with response/progression by serial tissue biopsies is logistically difficult. Use of liquid biopsies, including circulating tumor cells (CTC) and circulating tumor DNA (ctDNA), might provide highly informative, yet easily obtainable, evidence for better precision oncology care. Although ctDNA profiling has been well investigated, the CTC precision oncology genomic landscape and the advantages it may offer over ctDNA in ER-POS breast cancer remain largely unexplored. Whole-blood (WB) specimens were collected at serial time points from patients with advanced ER-POS/HER2-negative (NEG) advanced breast cancer in a phase I trial of AZD9496, an oral selective ER degrader (SERD) ET. Individual CTC were isolated from WB using tandem CellSearch® /DEPArray™ technologies and genomically profiled by targeted single-cell DNA next-generation sequencing (scNGS). High-quality CTC (n = 123) from 12 patients profiled by scNGS showed 100% concordance with ctDNA detection of driver estrogen receptor α (ESR1) mutations. We developed a novel CTC-based framework for precision medicine actionability reporting (MI-CTCseq) that incorporates novel features, such as clonal predominance and zygosity of targetable alterations, both unambiguously identifiable in CTC compared to ctDNA. Thus, we nominated opportunities for targeted therapies in 73% of patients, directed at alterations in phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), fibroblast growth factor receptor 2 (FGFR2), and KIT proto-oncogene, receptor tyrosine kinase (KIT). Intrapatient, inter-CTC genomic heterogeneity was observed, at times between time points, in subclonal alterations. Our analysis suggests that serial monitoring of the CTC genome is feasible and should enable real-time tracking of tumor evolution during progression, permitting more combination precision medicine interventions.

Treatment patterns, effectiveness, and patient-reported outcomes of palbociclib therapy in Chinese patients with advanced breast cancer: A multicenter ambispective real-world study

BACKGROUND

Palbociclib was the only available cyclin-dependent kinase 4/6 inhibitor in China until very recently, and its effect has not been systemically evaluated among Chinese patients. This study aims to assess the efficacy, safety and patient-reported outcomes (PROs) of palbociclib plus endocrine therapy (ET) in real-world China.

METHODS

An ambispective cohort study was conducted on patients with advanced HR+HER2- breast cancer who received palbociclib between July 2018, and November 2020 and were enrolled from 12 hospitals. Treatment patterns, survival outcomes, and safety events were documented, and PROs (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 items [EORTC QLQ-C30] and EuroQoL 5 dimensions [EQ-5D]) were analyzed. The Kaplan-Meier method was used to visualize and estimate the median progression-free survival (mPFS). Log-rank tests, Cox regressions, t tests, and chi-square tests were performed for comparison.

RESULTS

A total of 190 patients (median follow-up of 18.0 months) were enrolled. Palbociclib was mostly combined with aromatase inhibitors (66.3%), fulvestrant (32.6%), and tamoxifen (1.1%). The mPFS values were 21.0, 14.0, and 7.0 months with palbociclib administered in first- (n = 83), second- (n = 41) and subsequent-line settings (n = 66), respectively. Endocrine sensitivity was significantly associated with patient prognosis (mPFS: 23.0, 12.0, and 6.0 months for endocrine naïve, acquired, and primary resistant patients, respectively, p < 0.01). The outcome was worse for patients who failed to meet the inclusion criteria of PALOMA-3 than for those who met the criteria (later-line: 6.0 months vs. 9.0 months). The most common adverse events (AEs) were neutropenia (74.2%; grade 3/4: 30.0%), fatigue (48.4%), anemia (32.6%), and thrombocytopenia (22.1%). PRO data suggested that palbociclib plus ET significantly improved cognitive and emotional function, pain symptoms, and overall quality of life.

CONCLUSIONS

Palbociclib is effective for front-line use and for treating endocrine-sensitive patients in real-world China and is generally well tolerated. The prevalence of AEs in the Chinese population is different from that reported in the PALOMA-2/3 trials.

Overall Survival with Ribociclib plus Letrozole in Advanced Breast Cancer

BACKGROUND

In a previous analysis of this phase 3 trial, first-line ribociclib plus letrozole resulted in significantly longer progression-free survival than letrozole alone among postmenopausal patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether overall survival would also be longer with ribociclib was not known.

METHODS

Here we report the results of the protocol-specified final analysis of overall survival, a key secondary end point. Patients were randomly assigned in a 1:1 ratio to receive either ribociclib or placebo in combination with letrozole. Overall survival was assessed with the use of a stratified log-rank test and summarized with the use of Kaplan-Meier methods after 400 deaths had occurred. A hierarchical testing strategy was used for the analysis of progression-free survival and overall survival to ensure the validity of the findings.

RESULTS

After a median follow-up of 6.6 years, 181 deaths had occurred among 334 patients (54.2%) in the ribociclib group and 219 among 334 (65.6%) in the placebo group. Ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole. Median overall survival was 63.9 months (95% confidence interval [CI], 52.4 to 71.0) with ribociclib plus letrozole and 51.4 months (95% CI, 47.2 to 59.7) with placebo plus letrozole (hazard ratio for death, 0.76; 95% CI, 0.63 to 0.93; two-sided P = 0.008). No new safety signals were observed.

CONCLUSIONS

First-line therapy with ribociclib plus letrozole showed a significant overall survival benefit as compared with placebo plus letrozole in patients with HR-positive, HER2-negative advanced breast cancer. Median overall survival was more than 12 months longer with ribociclib than with placebo. (Funded by Novartis; MONALEESA-2 ClinicalTrials.gov number, NCT01958021.).

Estrogen Receptor and the Unfolded Protein Response: Double-Edged Swords in Therapy for Estrogen Receptor-Positive Breast Cancer

Estrogen receptor α (ERα) is a target for the treatment of ER-positive breast cancer patients. Paradoxically, it is also the initial site for estrogen (E₂) to induce apoptosis in endocrine-resistant breast cancer. How ERα exhibits distinct functions, in different contexts, is the focus of numerous investigations. Compelling evidence demonstrated that unfolded protein response (UPR) is closely correlated with ER-positive breast cancer. Treatment with antiestrogens initially induces mild UPR through ERα with activation of three sensors of UPR-PRK-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme 1α (IRE1α), and activating transcription factor 6 (ATF6)-in the endoplasmic reticulum. Subsequently, these sensors interact with stress-associated transcription factors such as c-MYC, nuclear factor-κB (NF-κB), and hypoxia-inducible factor 1α (HIF1α), leading to acquired endocrine resistance. Paradoxically, E₂ further activates sustained secondary UPR via ERα to induce apoptosis in endocrine-resistant breast cancer. Specifically, PERK plays a key role in inducing apoptosis, whereas IRE1α and ATF6 are involved in endoplasmic reticulum stress-associated degradation after E₂ treatment. Furthermore, persistent activation of PERK deteriorates stress responses in mitochondria and triggers of NF-κB/tumor necrosis factor α (TNFα) axis, ultimately determining cell fate to apoptosis. The discovery of E₂-induced apoptosis has clinical relevance for treatment of endocrine-resistant breast cancer. All of these findings demonstrate that ERα and associated UPR are double-edged swords in therapy for ER-positive breast cancer, depending on the duration and intensity of UPR stress. Herein, we address the mechanistic progress on how UPR leads to endocrine resistance and commits E₂ to inducing apoptosis in endocrine-resistant breast cancer.

A Randomized Trial of Fulvestrant, Everolimus, and Anastrozole for the Front-line Treatment of Patients with Advanced Hormone Receptor-positive Breast Cancer, SWOG S1222

PURPOSE

Metastatic hormone receptor (HR)-positive, HER2-negative breast cancer is an important cause of cancer mortality. Endocrine treatment with or without additional targeted therapies has been the mainstay of treatment. This trial was designed to evaluate the combination of fulvestrant plus everolimus versus fulvestrant, everolimus, and anastrozole compared with fulvestrant alone in the first-line treatment of advanced HR-positive, HER2-negative breast cancer.

PATIENTS AND METHODS

This randomized placebo-controlled trial included postmenopausal women with HR-positive, HER2-negative advanced breast cancer who had received no prior systemic therapy for metastatic disease. Participants were randomized to one of three treatment arms and the primary outcome was progression-free survival (PFS), comparing combinations of fulvestrant and everolimus with or without anastrozole with fulvestrant alone. Circulating tumor cells (CTC), as measured with two different methods, and circulating tumor DNA (ctDNA) were evaluated serially prior to treatment and the beginning of the second cycle of therapy.

RESULTS

Due in part to changes in clinical practice, the study was closed after accruing only 37 participants. There was no evidence that everolimus-containing combination treatment improved PFS or overall survival relative to fulvestrant alone. When modeled continuously, an association was observed of baseline CTC and ctDNA with poorer survival.

CONCLUSIONS

Although power of the study was limited, the findings were unable to support the routine use of everolimus combination endocrine therapy in the first-line treatment of advanced hormone-sensitive breast cancer. Prognostic impact of baseline ctDNA and copy-number variations in CTC was demonstrated.

A radiologist’s guide to novel anticancer therapies in the era of precision medicine

Novel anticancer agents have replaced conventional chemotherapy as first line agents for many cancers, with continued new and expanding indications. Small molecule inhibitors act on cell surface or intracellular targets and prevent the downstream signaling that would otherwise permit tumor growth and spread. Anticancer antibodies can be directed against growth factors or may be immunotherapeutic agents. The latter act by inhibiting mechanisms that cancer cells use to evade the immune system. Hormonal agents act by decreasing levels of hormones that are necessary for the growth of certain cancer cells. Cancer therapy protocols often include novel anticancer agents and conventional chemotherapy used successively or in combination, in order to maximize survival and minimize morbidity. A working knowledge of anti-cancer drug classification will aid the radiologist in assessing response on imaging.

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Novel anticancer agents include small molecule inhibitors, antibodies and hormones.

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These agents are predominantly cytostatic and inhibit factors that provide a survival advantage to tumor cells.

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Modern cancer therapy employs a combination of novel anticancer agents and conventional chemotherapy.

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It is essential for radiologists to have a broad understanding of these agents and their mechanisms of action.

Estrogen Receptor Bio-Activities Determine Clinical Endocrine Treatment Options in Estrogen Receptor-Positive Breast Cancer

In estrogen receptor positive (ER+) breast cancer therapy, estrogen receptors (ERs) are the major targeting molecules. ER-targeted therapy has provided clinical benefits for approximately 70% of all breast cancer patients through targeting the ERα subtype. In recent years, mechanisms underlying breast cancer occurrence and progression have been extensively studied and largely clarified. The PI3K/AKT/mTOR pathway, microRNA regulation, and other ER downstream signaling pathways are found to be the effective therapeutic targets in ER+ BC therapy. A number of the ER+ (ER+) breast cancer biomarkers have been established for diagnosis and prognosis. The ESR1 gene mutations that lead to endocrine therapy resistance in ER+ breast cancer had been identified. Mutations in the ligand-binding domain of ERα which encoded by ESR1 gene occur in most cases. The targeted drugs combined with endocrine therapy have been developed to improve the therapeutic efficacy of ER+ breast cancer, particularly the endocrine therapy resistance ER+ breast cancer. The combination therapy has been demonstrated to be superior to monotherapy in overall clinical evaluation. In this review, we focus on recent progress in studies on ERs and related clinical applications for targeted therapy and provide a perspective view for therapy of ER+ breast cancer.

Development of novel tetrahydroisoquinoline-hydroxamate conjugates as potent dual SERDs/HDAC inhibitors for the treatment of breast cancer

Concomitant inhibition of estrogen receptor alpha (ERα) and histone deacetylase (HDAC) signaling has been proven effective in endocrine-resistant ER+ breast cancers. Herein, a series of tetrahydroisoquinoline (THIQ)-hydroxamate conjugates were rationally designed and synthesized as dual SERDs/HDAC inhibitors by incorporating the hydroxamate, a known HDAC pharmacophore, into a privileged THIQ scaffold of selective ERα degraders (SERDs). Some of these THIQ-hydroxamate conjugates displayed remarkable HDAC6 inhibition and improved antiproliferative activity against MCF-7 cells. Particularly, the most potent HDAC inhibitor 19k also exhibits potent ERα binding affinity, good ERα degradation efficacy and the best antiproliferative activity. Besides, 19k displayed superior antitumor efficacy than the drug combination (Fulvestrant + SAHA) through promoting ERα degradation and histone acetylation in an MCF-7 xenograft model, without causing observable toxicity. Collectively, this study validates the therapeutic potential of a dual-acting compound with potent ERα degradation efficacy and HDAC6 inhibition in breast cancer.

Matching-Adjusted Indirect Comparison of Ribociclib Plus Fulvestrant versus Palbociclib Plus Letrozole as First-Line Treatment of HR+/HER2- Advanced Breast Cancer

Purpose

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) plus endocrine therapy are recommended for first-line treatment of hormone receptor–positive/human epidermal growth factor receptor 2–negative (HR+/HER2−) advanced breast cancer (ABC). However, not all CDK4/6i trials have reported significant overall survival (OS) benefit, and there have been no head-to-head trials. Two trials have reported OS outcomes in first-line patients: MONALEESA-3 reported significant OS benefit with first- or second-line ribociclib plus fulvestrant (RIB+FUL) versus placebo plus fulvestrant (PBO+FUL), while PALOMA-1 reported no significant OS benefit for palbociclib plus letrozole (PAL+LET) versus LET in first-line postmenopausal patients. Matched-adjusted indirect comparisons (MAICs) are an established method for comparing efficacy of treatments from different trials. We used an MAIC to compare first-line patients from MONALEESA-3 and PALOMA-1.

Patients and Methods

An unanchored MAIC of progression-free survival (PFS) and OS in first-line patients with HR+/HER2− ABC treated with RIB+FUL versus PAL+LET was conducted using individual patient data from MONALEESA-3 and aggregated data from PALOMA-1. To match patients in PALOMA-1, patients in MONALEESA-3 were limited to those with no prior endocrine therapy for ABC and no (neo) adjuvant LET ≤12 months before enrollment. PFS and OS were compared using Kaplan–Meier estimators and Cox regression.

Results

A total of 329 and 178 patients from RIB+FUL and PBO+FUL arms, respectively, of MONALEESA-3 were matched to 84 and 81 patients from PAL+LET and LET arms of PALOMA-1. After weighting, OS was significantly longer for RIB+FUL versus PAL+LET (hazard ratio [HR], 0.50; 95% CI, 0.32–0.77; p = 0.0020). PFS favored RIB+FUL versus PAL+LET, although the difference was not statistically significant (HR, 0.77; 95% CI, 0.54–1.10; p = 0.1553).

Conclusion

Using MAIC to adjust for trial differences, OS comparisons favored RIB+FUL over PAL+LET as first-line treatment in postmenopausal patients with HR+/HER2− ABC. These exploratory results suggest a significant increase in OS benefit with RIB treatment compared with PAL.

A Phase I Study of LSZ102, an Oral Selective Estrogen Receptor Degrader, with or without Ribociclib or Alpelisib, in Patients with Estrogen Receptor-Positive Breast Cancer

PURPOSE

Data are sparse for oral selective estrogen receptor (ER) degraders (SERD) in cancer treatment. The investigational oral SERD LSZ102 was assessed in monotherapy and combination use in a phase I study.

PATIENTS AND METHODS

A phase I, multicenter, open-label dose-escalation study (NCT02734615) of LSZ102 alone (arm A; n = 77) or with ribociclib (arm B; n = 78) or alpelisib (arm C; n = 43) in heavily pretreated adults with histologically confirmed ER-positive breast cancer and prior disease progression. Arm A received LSZ102 200-900 mg/day; arm B, LSZ102 200-600 mg/day plus ribociclib 300-600 mg/day; arm C, LSZ102 300-450 mg/day plus alpelisib 200-300 mg/day. Key outcomes were dose-limiting toxicities (DLT) in the first 28-day treatment cycle, adverse events (AE), laboratory parameters, pharmacokinetics, biopsy ER protein, and investigator-assessed clinical response (RECIST v1.1).

RESULTS

The most common AEs were gastrointestinal. Treatment-related serious AEs occurred in 10% of participants (19/198), mostly in arm C [10/43 (23%)]. DLTs occurred in: arm A, 5% (4/77); arm B, 3% (2/78); and arm C, 19% (8/43). LSZ102 exposure was slightly greater than dose proportional. On-treatment biopsy ER reductions were observed, with a trend toward an LSZ102 dose response. Objective response rates (95% confidence interval) were: arm A, 1.3% (0.0-7.0); arm B, 16.9% (9.3-27.1); and arm C, 7.0% (1.5-19.1), and clinical benefit rates 7.8% (2.9-16.2), 35.1% (24.5-46.8), and 20.9% (10.0-36.0), respectively.

CONCLUSIONS

LSZ102 was well tolerated alone and with ribociclib and had a manageable safety profile with alpelisib. Preliminary clinical activity was observed in combination use.

Palbociclib as an early-line treatment for Japanese patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: a review of clinical trial and real-world data

Breast cancer is the most common type of cancer among women worldwide and in Japan. The majority of breast cancers are hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2‒), and endocrine therapy is an effective therapy for this type of breast cancer. However, recent substantial advances have been made in the management of HR+/HER2‒ advanced breast cancer (ABC) with the advent of targeted therapies, such as cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, resulting in significant improvements in survival outcomes versus endocrine therapy alone. To evaluate the optimal use of palbociclib, a CDK4/6 inhibitor, in HR+/HER2- ABC, this review summarizes clinical trial and real-world data for palbociclib. In addition, current biomarker studies in palbociclib clinical research are reviewed. In Japanese patients, palbociclib was shown to be effective with a manageable safety profile, although differences were observed in the frequency of adverse event and dosing parameters. Current evidence supporting palbociclib as a first-line treatment strategy for patients with HR+/HER2‒ ABC in Asia, and specifically japan, is also discussed.

Real-World Efficacy of Fulvestrant Monotherapy as the First Treatment or Maintenance Treatment in Patients with Metastatic Breast Cancer

Background

Fulvestrant 500 mg monotherapy is recommended as the first-line endocrine treatment in postmenopausal women with hormone receptor-positive metastatic breast cancer (MBC). It is also used in MBC maintenance treatment. However, few studies have compared the efficacy of fulvestrant during the initial treatment with that during maintenance treatment.

Patients and Methods

MBC patients who were treated with fulvestrant either as initial therapy for metastatic disease or after progression following one line of chemotherapy between January 2016 and December 2017 were identified from the database of the Affiliated Hospital of Qingdao University. The primary end point was progression-free survival (PFS).

Results

The study included 135 MBC patients who were treated with fulvestrant; 116 patients who received fulvestrant as first-line treatment were divided into 2 groups: the no-chemotherapy treatment (NCT) group received fulvestrant as initial therapy during disease progression, and the chemotherapy treatment (CT) group received fulvestrant as maintenance following disease stabilization or response to previous chemotherapy. The median PFS was 16 months in NCT patients and 8 months in the CT group. Patients who had a longer disease-free survival, no visceral metastasis and one metastasis site, benefited from fulvestrant as first-line treatment during disease progression. Patients with 2 or more metastasis sites benefited from chemotherapy as first-line treatment and fulvestrant as maintenance treatment.

Conclusions

Fulvestrant monotherapy showed good clinical activity and safety in patients with MBC who were treated upon disease progression and in those receiving maintenance therapy.

Experimental models of endocrine responsive breast cancer: strengths, limitations, and use

Breast cancers characterized by expression of estrogen receptor-alpha (ER; ESR1) represent approximately 70% of all new cases and comprise the largest molecular subtype of this disease. Despite this high prevalence, the number of adequate experimental models of ER+ breast cancer is relatively limited. Nonetheless, these models have proved very useful in advancing understanding of how cells respond to and resist endocrine therapies, and how the ER acts as a transcription factor to regulate cell fate signaling. We discuss the primary experimental models of ER+ breast cancer including 2D and 3D cultures of established cell lines, cell line- and patient-derived xenografts, and chemically induced rodent models, with a consideration of their respective general strengths and limitations. What can and cannot be learned easily from these models is also discussed, and some observations on how these models may be used more effectively are provided. Overall, despite their limitations, the panel of models currently available has enabled major advances in the field, and these models remain central to the ability to study mechanisms of therapy action and resistance and for hypothesis testing that would otherwise be intractable or unethical in human subjects.

Management of hormone receptor-positive, human epidermal growth factor 2-negative metastatic breast cancer

Estrogen receptor (ER) is the major driver of most metastatic breast cancers (mBCs). Endocrine therapy (ET) is the most effective treatment for ER + mBC, but its effectiveness is limited by high rates of de novo and acquired resistance. A growing understanding of the biological characteristics and complexity of the ER pathway and the mechanisms of ET resistance has led to the development of a new generation of targeted therapies. One such mechanism is the cell cycle signaling pathways, which lead to the development of cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) that have, in turn, transformed the management of such tumors. Another important mechanism is the alteration of the phosphatidylinositol 3'-kinase/AKT/mammalian target of rapamycin pathway. Drugs targeting each component of these pathways are currently used in clinical practice, and several more are in development. As a result, a myriad of new targeted therapies are consistently being added to the clinical oncologist armamentarium. Navigating the evolving and highly complex treatment landscape of HR + /HER2- mBC remains both an art and a challenge. In this review, we discuss the biological features of HR + /HER2- mBC and the different mechanisms of resistance to ET. We also discuss the management of mBC as the disease changes from endocrine-sensitive to endocrine-resistant.

Response to Induction Neoadjuvant Hormonal Therapy Using Upfront 21-Gene Breast Recurrence Score Assay-Results From the SAFIA Phase III Trial

Luminal, human epidermal growth factor receptor 2–negative breast cancer represents the most common subtype of breast malignancies. Neoadjuvant strategies of operable breast cancer are mostly based on chemotherapy, whereas it is not completely understood which patients might benefit from neoadjuvant hormone therapy (NAHT).

Current and emerging estrogen receptor-targeted therapies for the treatment of breast cancer

Nearly 80% of all breast cancers are estrogen receptor positive (ER+) and require the activity of this transcription factor for tumor growth and survival. Thus, endocrine therapies, which target the estrogen signaling axis, have and will continue to be the cornerstone of therapy for patients diagnosed with ER+ disease. Several inhibitors of ER activity exist, including aromatase inhibitors (AIs), selective estrogen receptor modulators (SERMs), selective estrogen receptor degraders/down-regulators (SERDs), and ER proteolysis-targeting chimeras (ER PROTACs); drugs which differ in the mechanism(s) by which they inhibit this signaling pathway. Notwithstanding their significant impact on the management of this disease, resistance to existing endocrine therapies remains a major impediment to durable clinical responses. Although the mechanisms of resistance are complex and varied, dependence on ER is typically retained after progression on SERMs and AIs, suggesting that ER remains a bona fide therapeutic target. The discovery and development of orally bioavailable drugs that eliminate ER expression (SERDs and ER PROTACs) will likely aid in treating this growing patient population. All of the existing endocrine therapies were developed with the intent of inhibiting the cancer cell intrinsic actions of ER and/or with the objective of achieving extreme estrogen deprivation and most achieve that goal. A longstanding question that remains to be addressed, however, is how actions of existing interventions extrinsic to the cancer cells influence tumor biology. We believe that these issues need to be addressed in the development of strategies to develop the next generation of ER-modulators optimized for positive activities in both cancer cells and other cells within the tumor microenvironment (TME).

Dynamics-Based Discovery of Novel, Potent Benzoic Acid Derivatives as Orally Bioavailable Selective Estrogen Receptor Degraders for ERα+ Breast Cancer

The estrogen receptor α (ERα) is identified as an effective target for the treatment of ERα+ breast cancer; thus, discovery of novel selective estrogen receptor degraders (SERDs) are developed as an effective method to overcome the resistance of breast cancer. Herein, the hot-spot residues for protein-ligand interaction between SERDs and ERα are analyzed by molecular dynamic simulation technology, focusing on the hot-spot residues for four series of designed and synthesized SERDs. SAR studies revealed that while the acrylic acid moiety of AZD9496 is scaffold hopping into benzoic acid, compound D24 exhibits potent binding affinity with ERα, good degradation efficacy of ERα, and inhibitory effect against the MCF-7 breast cancer cell line. Besides, D24 also displays good antitumor efficacy in the MCF-7 human breast cancer xenograft model in vivo, favorable pharmacokinetic properties, excellent druggability, and good safety property, making D24 as a promising drug candidate of SERD for further evaluation.

Breast Cancer Therapeutics and Biomarkers: Past, Present, and Future Approaches

Breast cancer (BC) is the leading cause of cancer death in women and the second-most common cancer. An estimated 281 550 new cases of invasive BC will be diagnosed in women in the United States, and about 43 600 will die during 2021. Continual research has shed light on all disease areas, including tumor classification and biomarkers for diagnosis/prognosis. As research investigations evolve, new classes of drugs are emerging with potential benefits in BC treatment that are covered in this manuscript. The initial sections present updated classification and terminology used for diagnosis and prognosis, which leads to the following topics, discussing the past and present treatments available for BC. Our review will generate interest in exploring the complexity of the cell cycle and its association with cancer biology as part of the plethora of target factors toward developing newer drugs and effective therapeutic management of BC.

Endocrine-Based Treatments in Clinically-Relevant Subgroups of Hormone Receptor-Positive/HER2-Negative Metastatic Breast Cancer: Systematic Review and Meta-Analysis

A precise assessment of the efficacy of first-/second-line endocrine therapies (ET) ± target therapies (TT) in clinically-relevant subgroups of hormone receptor-positive (HR+)/HER2-negative metastatic breast cancer (MBC) has not yet been conducted. To improve our current knowledge and support clinical decision-making, we thus conducted a systematic literature search to identify all first-/second-line phase II/III randomized clinical trials (RCT) of currently approved or most promising ET ± TT. Then, we performed a meta-analysis to assess progression-free (PFS) and/or overall survival (OS) benefit in several clinically-relevant prespecified subgroups. Thirty-five RCT were included (17,595 patients). Pooled results show significant reductions in the risk of relapse or death of 26-41% and 12-27%, respectively, depending on the clinical subgroup. Combination strategies proved to be more effective than single-agent ET (PFS hazard ratio (HR) range for combinations: 0.60-0.65 vs. HR range for single agent ET: 0.59-1.37; OS HR range for combinations: 0.74-0.87 vs. HR range for single agent ET: 0.68-0.98), with CDK4/6-inhibitors(i) + ET being the most effective regimen. Single agent ET showed comparable efficacy with ET+TT combinations in non-visceral (p = 0.63) and endocrine sensitive disease (p = 0.79), while mTORi-based combinations proved to be a valid therapeutic option in endocrine-resistant tumors, as well as PI3Ki + ET in PIK3CA-mutant tumors. These results strengthen international treatment guidelines and can aid therapeutic decision-making.

Real-world data of fulvestrant as first-line treatment of postmenopausal women with estrogen receptor-positive metastatic breast cancer

Goals of endocrine therapy for advanced breast cancer (ABC) include prolonging survival rates, maintaining the quality of life, and delaying the initiation of chemotherapy. We evaluated the effectiveness of fulvestrant as first-line in patients with estrogen receptor (ER)-positive ABC with relapse during or after adjuvant anti-estrogenic therapy in real-world settings. Retrospective, observational study involving 171 postmenopausal women with ER-positive ABC who received fulvestrant as first-line between January 2011 and May 2018 in Spanish hospitals. With a median follow-up of 31.4 months, the progression-free survival (PFS) with fulvestrant was 14.6 months. No differences were seen in the visceral metastatic (14.3 months) versus non-visceral (14.6 months) metastatic subgroup for PFS. Overall response rate and clinical benefit rate were 35.2% and 82.8%. Overall survival was 43.1 months. The duration of the clinical benefit was 19.2 months. Patients with ECOG performance status 0 at the start of treatment showed a significant greater clinical benefit rate and overall survival than with ECOG 1–2. Results in real-world settings are in concordance with randomized clinical trials. Fulvestrant continues to demonstrate clinical benefits in real-world settings and appears be well tolerated as first-line for the treatment of postmenopausal women with ER-positive ABC.

Meta-analyses of visceral versus non-visceral metastatic hormone receptor-positive breast cancer treated by endocrine monotherapies

Endocrine therapy (ET) is recommended as first-line therapy for the majority of patients with hormone receptor-positive (HR+), human epidermal growth factor 2-negative advanced breast cancer (ABC); however, the efficacy of ET in patients with visceral metastases (VM) versus patients whose disease is limited to non-visceral metastases (non-VM) is debated. Meta-analyses including available data from randomised controlled trials of first- and second-line endocrine monotherapies for patients with HR+ ABC were performed to address this question. In one and two-stage meta-analyses, progression-free survival (PFS), overall survival (OS), clinical benefit rate (CBR) and duration of clinical benefit (DoCB) outcomes were analysed. In the first-line meta-analysis (seven trials; n = 1988) tamoxifen and fulvestrant significantly improved PFS, OS and CBR for patients with non-VM versus those whose disease included VM. The most substantial hazard ratios were observed for fulvestrant 500 mg; 0.56 (95% confidence interval [CI] 0.45-0.70) and 0.55 (95% CI 0.42-0.72) for PFS and OS, respectively. In the second-line meta-analysis (seven trials; n = 2324), all ET combined was more effective (in terms of PFS, OS and DoCB) for non-VM versus VM. In both meta-analyses, patients with non-liver VM had better clinical outcomes than patients with liver VM for all types of ET. Patients whose disease included non-VM sites had better clinical outcomes with endocrine monotherapy compared with patients whose disease included VM. These findings may facilitate better informed treatment decision-making.

Aromatase and CDK4/6 Inhibitor-Induced Musculoskeletal Symptoms: A Systematic Review

BACKGROUND

Treatment with aromatase inhibitors (AIs) is fundamental in women with hormone receptor-positive breast cancer in the adjuvant as well as the metastatic setting. Even though it is considered to be a well-tolerated therapy, aromatase inhibitor-associated musculoskeletal syndrome (AIMSS) is the most common adverse event encountered by breast cancer patients. CDK4/6 inhibitors have emerged as a new treatment strategy in metastatic hormone receptor-positive breast cancer. However, the impact of CDK4/6 inhibitors on musculoskeletal symptoms caused by AIs is not well-defined.

OBJECTIVES

This systematic review aims to identify the frequency of joint symptoms induced by treatment with AIs and CDK4/6 inhibitors in the metastatic setting.

SEARCH STRATEGY

Eligible articles were identified by a search of existing literature for the period 2005/01/01-2021/01/01; The algorithm consisted of a predefined combination of the following keywords "breast", "cancer", "aromatase inhibitors", "CDK4/6", "phase III".

SELECTION CRITERIA

This study was performed in accordance with PRISMA guidelines. All randomized controlled Phase III trials (RCTs) evaluating the administration of third-generation aromatase inhibitors (AIs) and CDK4/6 inhibitors in postmenopausal women in the metastatic setting were considered eligible for this review.

DATA COLLECTION

Overall, 16 randomized control trials (RCTs) were retrieved, of which nine studies explored the administration of AIs in the metastatic setting and seven studies investigated the combination of CDK4/6 inhibitors and AIs. Arthralgia was reported in 1-47% of patients treated with AIs and 5.8-33.3% of patients treated with CDK4/6 inhibitors. Myalgias occurred in 2-23.7% of patients receiving AIs compared with 4.8-11.9% of patients treated with CDK4/6 inhibitors. The incidence of back pain was 7-32.9% vs. 2.9-8.5% in postmenopausal women with metastatic disease treated with AIs and CDK4/6 inhibitors, respectively. Bone pain was reported in 7-32.9% of postmenopausal women treated with AIs and 2.9-8.5% of women treated with CDK4/6 inhibitors.

CONCLUSIONS

AI treatment-induced musculoskeletal syndrome is an adverse event affecting over one-third (20-47%) of postmenopausal patients treated with AIs that often leads to treatment discontinuation. Data from RCTs provide evidence that the incidence of musculoskeletal symptoms is relatively decreased upon CDK4/6 inhibitor administration. CDK4/6 inhibitors may provide a protective role against AIMSS development.

Meta-analyses of phase 3 randomised controlled trials of third generation aromatase inhibitors versus tamoxifen as first-line endocrine therapy in postmenopausal women with hormone receptor-positive advanced breast cancer

BACKGROUND

Four randomised controlled trials (RCTs) in postmenopausal women with advanced breast cancer (ABC) comparing aromatase inhibitors (AIs) versus the selective estrogen receptor modulator tamoxifen, each individually reported significantly longer progression-free survival (PFS) but none showed a significant difference in overall survival (OS). In these trials between 6.8% and 55% of tumours were hormone receptor (HR) status unknown or negative. This meta-analysis restricted the comparison to HR-positive (HR+) tumours.

METHODS

Anonymised individual patient data were obtained from three RCTs, EORTC (exemestane versus tamoxifen), Study 0027 and Study 0030 (both anastrozole versus tamoxifen). For the remaining RCT (Femara Study PO25; letrozole versus tamoxifen), odds ratio (OR) or hazard ratio (HzR), with confidence intervals were obtained from the clinical study report, for patients with HR+ tumours, in addition to published data. In total, data were obtained from 2296 patients; 1560 (68%) had HR+ ABC.

FINDINGS

The OR for clinical benefit rate was 1.56, in favour of AIs (p < 0.001). The duration of clinical benefit was not significantly increased by AIs (HzR 0·88; p = 0.08). For PFS the HzR (0.82) was in favour of AIs (p = 0·007). However, for OS the HzR (1.05) was not significantly different between AIs and tamoxifen (p = 0.42).

INTERPRETATION

Although third generation AIs put significantly more patients into 'clinical benefit', their tumours were not controlled for significantly longer. Overall, while this resulted in a significantly greater PFS in favour of the AIs, this did not translate into improvement in OS.

Clinical Challenges in the Management of Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer: A Literature Review

Endocrine therapy (ET) is integral to the treatment of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). Aromatase inhibitors (AIs; e.g., anastrozole, letrozole, exemestane), selective estrogen receptor modulators (e.g., tamoxifen), and the selective estrogen receptor degrader, fulvestrant, inhibit tumor cell proliferation by targeting ER signaling. However, the efficacy of ET could be limited by intrinsic and acquired resistance mechanisms, which has prompted the development of targeted agents and combination strategies. In recent years, the treatment landscape for HR+, HER2- MBC has evolved rapidly. AIs, historically the first-line treatment for postmenopausal patients with HR+, HER2- MBC, have been challenged by more effective ET, such as fulvestrant alone or in combination with an AI, and the cyclin-dependent kinase (CDK)4/6 inhibitors, which have increasingly become the new standard of care. For endocrine-resistant disease (≥ second-line), clinical trials demonstrated that the mammalian target of rapamycin inhibitor, everolimus, enhanced the efficacy of exemestane or fulvestrant after progression on an AI. CDK4/6 inhibitors in combination with fulvestrant have demonstrated superior progression-free survival and overall survival versus fulvestrant alone. Recently, the combination of fulvestrant with alpelisib in phosphatidylinositol-4,5-bisphosphate 3-kinase (PIK3CA) mutated HR+, HER2- MBC following progression on or after ET was approved, based on the SOLAR-1 study. However, the optimal sequencing of treatments is unknown, especially following disease progression on a CDK4/6 inhibitor. This review aims to provide practical guidance for the management of HR+, HER2- MBC based on available data and the utility of genomic biomarkers, including germline breast cancer genes 1 and 2 (BRCA1/2) mutations, and somatic estrogen receptor alpha gene (ESR1), HER2, and PIK3CA mutations.

Cost-effectiveness of pembrolizumab for treatment of platinum-resistant recurrent or metastatic head and neck squamous cell carcinoma in China: an economic analysis based on a randomised, open-label, phase III trial

BACKGROUND

Pembrolizumab was recently demonstrated to have survival benefit in patients with recurrent or metastatic head and neck squamous cell carcinoma (r/mHNSCC). However, the cost-effectiveness of pembrolizumab versus chemotherapy in China remains uncertain.

OBJECTIVE

This analysis aimed to describe the cost-effectiveness of pembrolizumab versus standard-of-care (SOC) therapy in r/mHNSCC in China.

DESIGN

A Markov model consisting of three health states (stable, progressive and dead) was developed to compare the cost and effectiveness of pembrolizumab with SOC in platinum-resistant r/mHNSCC. Model inputs for transition probabilities and toxicity were collected from the KEYNOTE-040 trial, while health utilities were estimated from a literature review. Cost data were acquired for the payer's perspective in China. Costs and outcomes were discounted at an annual rate of 3.0%. Sensitivity analyses were conducted to test the uncertainties surrounding model parameters.

OUTCOME MEASURES

The primary outcome was incremental cost-effectiveness ratios (ICERs), which were calculated as the cost per quality-adjusted life years (QALYs).

RESULTS

The total mean cost of pembrolizumab and SOC was US$45 861 and US$41 950, respectively. As for effectiveness, pembrolizumab yielded 0.31 QALYs compared with 0.25 QALYs for SOC therapy. The ICER for pembrolizumab versus SOC was US$65 186/QALY, which was higher than the willingness-to-pay threshold (WTP) of US$28 130/QALY in China. The univariate sensitivity analysis indicated that utility values for progressive state, probability from stable to progressive in the SOC group, as well as cost of pembrolizumab were the three most influential variables on ICER. The probabilistic sensitivity analysis demonstrated that standard therapy was more likely to be cost-effective compared with pembrolizumab at a WTP value of US$28 130/QALY. Results were robust across both univariate analysis and probabilistic sensitivity analysis.

CONCLUSIONS

Pembrolizumab is not likely to be a cost-effective strategy compared with SOC therapy in patients with platinum-resistant r/mHNSCC in China.

TRIAL REGISTRATION NUMBER

NCT02252042; Post-results.

Clinical Outcomes of 130 Patients with Hormone Receptor-Positive and Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer Treated with Palbociclib plus Endocrine Therapy and Subsequent Therapy: A Real-World Single-Center Retrospective Study in China

BACKGROUND This retrospective single-center study conducted in China aimed to investigate the clinical outcomes of patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC) treated with palbociclib plus endocrine therapy (ET) and subsequent therapy. MATERIAL AND METHODS Eligible patients were women with HR+ and HER2- MBC who initiated palbociclib plus ET between September 2016 and August 2019 at Fudan University Shanghai Cancer Center. Clinical characteristics and efficacy data were retrospectively recorded from the electronic medical record system. RESULTS In total, 130 patients were included in the study, of whom 87.0% of patients started palbociclib on 125 mg/day, 8.5% of patients had dose reduction, and 2.3% of patients discontinued the treatment because of toxicity. Overall, the disease control rate was 77.4% and clinical benefit rate was 63.4%. After a median follow-up period of 10.6 months, the median progression-free survival was 9.2 months. There was limited efficacy in patients who received palbociclib as no less than a fourth line of ET, except for patients who added palbociclib to the ET, which they had acquired resistance to. After disease progression on palbociclib, further treatment with chemotherapy and ET had similar efficacy (P=0.571). CONCLUSIONS The findings from this real-world single-center study in China showed that treatment with palbociclib plus ET exhibited favorable efficacy and good tolerance in patients with HR+ and HER2- MBC, even in patients who were initially resistant to endocrine therapy, and there was no difference in outcomes between subsequent treatment with chemotherapy and ET.

A Phase II Study of Fulvestrant 500 mg as Maintenance Therapy in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Patients with Advanced Breast Cancer After First-Line Chemotherapy

LESSONS LEARNED

Fulvestrant 500 mg maintenance therapy showed a clinical benefit rate of 76% and median progression-free survival of 16.1 months in patients who achieved objective responses or disease control after first-line chemotherapy. Adverse events with fulvestrant maintenance therapy were consistent with the known safety profile of the drug.

BACKGROUND

Evidence for maintenance hormonal therapy after chemotherapy for estrogen receptor (ER)-positive/human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer is scarce. This study aimed to evaluate the efficacy of fulvestrant 500 mg maintenance therapy in patients after first-line chemotherapy.

METHODS

We enrolled postmenopausal women with ER-positive/HER2-negative advanced breast cancer who attained tumor responses or disease control with four to eight cycles of chemotherapy as first-line treatment. Fulvestrant 500 mg was injected on days 1, 15, and 29 and every 28 (±3) days thereafter. The primary endpoint was the clinical benefit rate (CBR); the secondary endpoints included the objective response rate (ORR), progression-free survival (PFS), and safety.

RESULTS

We included 58 patients; the median follow-up duration was 32.6 months. The CBR since commencing fulvestrant maintenance therapy was 76% (95% confidence interval [CI], 63%-86%), and ORR was 14% (95% CI, 6%-25%); eight patients achieved partial response. The median PFS for fulvestrant maintenance therapy was 16.1 months (95% CI, 10.3-21.0 months). Thirty-nine patients (67%) reported at least one adverse event, of which most were grade 1/2, whereas three patients (5%) reported grade 3 adverse events.

CONCLUSION

Fulvestrant 500 mg is a feasible and promising hormonal maintenance strategy in patients with ER-positive/HER2-negative advanced breast cancer who have no disease progression after first-line chemotherapy.

Ribociclib plus fulvestrant in the treatment of breast cancer

INTRODUCTION

Endocrine therapy (ET) is a standard first-line treatment for hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC) Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have demonstrated significantly improved progression-free survival (PFS) with ET in patients with ABC. Recent reports indicate that the addition of the CDK4/6i ribociclib to ET, including fulvestrant, significantly improves PFS and overall survival (OS).

AREAS COVERED

This review summarizes the efficacy and safety of ribociclib plus fulvestrant in HR+/HER2- ABC and its role in clinical practice. Various post-progression strategies are discussed.

EXPERT OPINION

In MONALEESA-3, ribociclib +fulvestrant significantly improved PFS and OS in postmenopausal patients who received no prior chemotherapy and ≤1 prior line of ET for ABC and benefited many patient subgroups, including those with visceral metastases and ET resistance. The safety of this combination is manageable and consistent with the known safety profile of ribociclib, with myelosuppression being a common and expected toxicity; other relevant toxicities requiring monitoring that occur at a low rate include hepatobiliary toxicity, pneumonitis, and QTc prolongation. There is an important role for CDK4/6i + ET, including ribociclib + fulvestrant, in clinical practice. The optimal position of CDK4/6i in first or subsequent lines of treatment and the optimal post-CDK4/6i progression strategies are not yet elucidated.

Therapy Algorithms for the Diagnosis and Treatment of Patients with Early and Advanced Breast Cancer

Background

In order to offer optimal treatment approaches based on available evidence, the Commission Breast of the Working Group Gynecologic Oncology (AGO) of the German Cancer Society developed therapy algorithms for eight complex treatment situations in primary and advanced breast cancer.

Summary

Therapy algorithms for the following complex treatment situations are outlined in this paper: (neo)adjuvant therapy of human epidermal growth factor receptor 2 (HER2)-positive breast cancer; axillary surgery and neoadjuvant chemotherapy; adjuvant endocrine therapy in premenopausal patients; adjuvant endocrine therapy in postmenopausal patients; hormone receptor (HR)-positive/HER2-negative metastatic breast cancer: strategies; HR-positive/HER2-negative metastatic breast cancer: endocrine-based first-line treatment; HER2-positive metastatic breast cancer: first to third-line; metastatic triple-negative breast cancer.

Key Messages

The therapy options shown in these algorithms are based on the current AGO recommendations updated in January 2020 but cannot represent all evidence-based treatment options. Prior therapies, performance status, comorbidities, patient preference, etc. must be taken into account for the actual treatment choice. Therefore, in individual cases, other evidence-based treatment options not listed here may also be appropriate and justified.

Development and validation of a nomogram in survival prediction among advanced breast cancer patients

Background

The overall survival (OS) among patients with advanced breast cancer (ABC) varies greatly. Although molecular subtype is known as the most important factor in OS differentiation, significant differences in OS among patients with the same molecular subtype still occur, leading to the need for a more accurate prognostic prediction model. This study aimed to develop a prediction model (nomogram) based on current diagnosis and treatment to predict the OS of newly diagnosed ABC patients in China.

Methods

From the institution’s database, we collected data of 368 ABC patients from Sun Yat-sen Memorial Hospital (national hospital) as a training set to establish a nomogram with prognostic risk factors that calculated the predicted probability of survival. Nomograms were independently validated with 278 patients with ABC from two other institutions using the concordance index (C-index), calibration plots and risk group stratifications.

Results

The initial primary tumor stage, molecular subtype, disease-free survival (DFS), presence of brain metastasis, and the tumor burden of metastasis disease (local recurrence, oligo-metastatic disease, or multiple-metastatic disease) were included in the prognostic nomogram. The nomogram had a C-index of 0.77 and 0.71 in the training and the validation sets, respectively. The nomogram was able to stratify patients into different risk groups, respectively (HR 6.81, 95% CI: 4.69 to 9.89, P<0.001). In the lower risk score group (risk score <11), there was no significant difference between the OS with chemotherapy and hormone therapy (HR 0.81, 95% CI: 0.44 to 1.47, P=0.48).

Conclusions

We have constructed a novel prediction nomogram that can guide the physicians to select personalized treatment options. Furthermore, our study is the first to add oligo-metastatic disease and primary endocrine/trastuzumab resistance into the prognostic models.