Endocrine Treatment and Targeted Therapy for Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Metastatic Breast Cancer: ASCO Guideline Update

Oral Anticancer Therapies: Addressing Nonadherence in Patients With Breast Cancer

This review aims to investigate the issue of treatment nonadherence and to present the available strategies to improve adherence to oral treatments in breast cancer. A literature search was conducted to contextualise the issue of nonadherence, investigate the reasons behind nonadherence, and demonstrate strategies to address treatment nonadherence in breast cancer. Findings indicate that adherence rates decrease while discontinuation rates increase with increasing lengths of breast cancer treatment course. Lack of adherence is proven to be detrimental to treatment outcomes. Patients struggle to adhere to treatment due to inadequate relationships with healthcare providers, lack of information, psychological distress, and side effects. Healthcare providers should evaluate patient's experience to provide the necessary support. Following this assessment, healthcare providers may recommend interventions addressing patient knowledge, psychological distress or side effects. Treatment adherence remains an issue for oral therapeutics in breast cancer. After patient assessment, healthcare providers can offer personalised strategies to improve treatment adherence. The most crucial interventions address patient knowledge, psychological distress, and side effects.

Explaining the Relationships Between Age, Endocrine Therapy Persistence, and Risk of Recurrence in Hormone Receptor-Positive Early Breast Cancer: A Nationwide Cohort Study

PURPOSE

Young age is associated with increased risk of recurrence in hormone receptor (HR)-positive early-stage breast cancer (eBC). Lack of adherence to endocrine therapy (ET) is a potential reason for the lower survival proportions observed in younger patients, but the survival benefits of improving adherence to ET in young patients remain unknown.

MATERIALS AND METHODS

Using data from the French National Health Data System and target trial emulation methods, we considered three sustained ET persistence strategies (allowing treatment gaps of no more than 30, 90, or 180 continuous days) and estimated the 5-year disease-free survival (DFS) benefit of sustained ET persistence compared with observed ET persistence.

RESULTS

A total of 121,601 patients with HR-positive eBC were included in the analyses, of whom 29.8% was younger than 50 years at diagnosis. Younger patients had lower DFS and were more likely to discontinue ET than older patients. In patients 34 years and younger, strict ET persistence (≤30-day gaps) improved 5-year DFS proportions from 74.5% to 78.8% (4.3 percentage points [95% CI, 2.6 to 7.2]) compared with observed persistence. ET persistence strategies allowing for ≤90-day and ≤180-day gaps reduced the 5-year DFS benefit in patients 34 years and younger to 1.3 (95% CI, 0.2 to 3.7) and 1.0 (95% CI, -0.2 to 3.4) percentage points, respectively. By contrast, DFS benefits of improved ET persistence in patients after 50 years old did not exceed 1.9 percentage points, compared with observed persistence, regardless of the persistence definition.

CONCLUSION

The survival benefit that could be achieved with strict ET persistence in women 34 years and younger with HR-positive eBC highlights the need for tailored strategies to improve ET persistence in this population.

Treatment patterns and outcomes in HER2-low metastatic breast cancer patients previously treated with chemotherapy: a US real-world cohort study

PURPOSE

Real-world outcomes are poorly understood for patients with human epidermal growth factor receptor 2 (HER2)-low (immunohistochemistry 1+ or 2+ with negative in situ hybridization) metastatic breast cancer (mBC).

METHODS

Using for the first time a nationwide electronic health record-derived de-identified database, we assessed demographics, treatment patterns, and outcomes of patients with HER2-low mBC who previously received one line of chemotherapy in the metastatic setting. The post-chemotherapy line was termed the index line of therapy (LOT).

RESULTS

3765 patients [hormone receptor (HR)-positive: 78.8%, HR-negative: 21.0%] met the inclusion criteria (1 January 2011-30 April 2023). 61.7% of HR-positive patients received endocrine therapy prior to the index LOT. The largest patient percentage received single-agent chemotherapy at the index and subsequent two LOTs. For the overall cohort, the median real-world time to treatment discontinuation/death was 4.1 months (95% CI: 3.9-4.2) and the median real-world time to next treatment/death was 5.1 months (95% CI: 4.8-5.3) from the index LOT. Median real-world overall survival (all patients) was 15.8 months (95% confidence interval: 15.2-16.5, median follow-up = 54.5 months) from the index LOT.

CONCLUSION

These data highlight the unmet clinical needs of patients with HER2-low mBC by characterizing the treatment patterns and poor outcomes in this population on the current standard of care.

Real-world evidence from Japan regarding survival outcomes and treatment sequence in patients receiving CDK4/6 inhibitor plus endocrine therapy as first- or second-line treatment for hormone receptor-positive, HER2-negative advanced or metastatic breast cancer

BACKGROUND

A cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) plus endocrine therapy (ET) is a current standard first-/second-line treatment for hormone receptor (HR)-positive, HER2-negative advanced/metastatic breast cancer (AMBC). We aimed to provide real-world evidence regarding CDK4/6i therapy in this population.

METHODS

In this multicenter observational study, data from patients who had started CDK4/6i therapy between January 1, 2019, and December 31, 2021, as first-/second-line treatment for AMBC were used; real-world progression-free survival (rwPFS), chemotherapy-free survival, and overall survival were analyzed using the Kaplan-Meier method. Additionally, data were analyzed by separating patients with treatment-free interval (TFI) < 12 months (deemed resistant to ET) from the first-line treatment group (hereafter, the exclusive first-line treatment group).

RESULTS

Data from 745 patients were analyzed. Compared with palbociclib, abemaciclib was used in younger patients and those with expected poor prognosis. Median rwPFS was 36.8, 17.8, and 31.4 months in patients with de novo stage IV disease, TFI < 12 months, and TFI ≥ 12 months, respectively, in the first-line treatment group, and 17.4 months in the second-line treatment group. In the exclusive first-line treatment group, median rwPFS of the subsequent treatment after initial CDK4/6i plus ET was < 7 months, regardless of the type of subsequent treatment; prognosis was especially poor in those who were switched to chemotherapy.

CONCLUSIONS

The real-world survival outcomes found in this study for patients receiving first-/second-line CDK4/6i therapy were consistent with those of randomized phase 3 studies. As outcomes of subsequent treatment after initial CDK4/6i plus ET remain insufficient, further improvement in treatment is necessary.

Inavolisib plus letrozole or fulvestrant in PIK3CA-mutated, hormone receptor-positive, HER2-negative advanced or metastatic breast cancer (GO39374): An open-label, multicentre, dose-escalation and dose-expansion phase 1/1b study

BACKGROUND

A variety of treatment options continue to be explored in the post-cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) setting for hormone receptor (HR)-positive, HER2-negative locally advanced/metastatic breast cancer (LA/mBC), and optimal sequencing of therapies remains to be determined. This phase 1/1b study examined inavolisib, a potent and selective PI3Kα inhibitor that promotes mutated p110α degradation, alone and in combination with endocrine therapy (ET) ± palbociclib, in PIK3CA-mutated, HR-positive, HER2-negative LA/mBC. We report data on inavolisib plus ET, including in patients who had previously received a CDK4/6i.

METHODS

Women age ≥ 18 years received inavolisib (6 mg/9 mg orally once daily [PO QD]) plus letrozole (2·5 mg PO QD), or inavolisib (9 mg PO QD) plus fulvestrant (500 mg intramuscularly on Days 1 and 15 of Cycle 1 then every 4 weeks), until unacceptable toxicity/disease progression.

PRIMARY ENDPOINT

safety and tolerability.

FINDINGS

Thirty-seven and 60 patients were enrolled in the inavolisib plus letrozole and inavolisib plus fulvestrant arms, respectively. Overall, treatment-related adverse events (mostly low grade) occurred in 94·6 % and 93·3 % of patients, respectively; the most frequent (≥10 % of patients in either arm) were hyperglycaemia, stomatitis, nausea, and diarrhoea. Confirmed objective response rates in patients with measurable disease were 9·7 % and 25·9 %, respectively; median progression-free survival was 3·7 and 7·3 months. Among patients with previous CDK4/6i therapy (29/37 and 58/60 patients, respectively), confirmed objective response rates were 13·0 % and 25·0 %; median progression-free survival was 3·7 and 7·1 months. No drug-drug interactions were observed for any study treatment. Paired baseline and Cycle 1 Day 15 tumour biopsies and circulating tumour DNA analyses demonstrated the impact of study treatment on pharmacodynamic/pathophysiologic biomarkers of response.

INTERPRETATION

Inavolisib plus ET demonstrated a manageable safety profile and encouraging preliminary anti-tumour activity in patients with PIK3CA-mutated, HR-positive, HER2-negative LA/mBC, including those in the post-CDK4/6i setting.

FGFR2-RUNX2 activation: An unexplored therapeutic pathway in luminal breast cancer related to tumor progression

Overcoming luminal breast cancer (BrCa) progression remains a critical challenge for improved overall patient survival. RUNX2 has emerged as a protein related to aggressiveness in triple-negative BrCa, however its role in luminal tumors remains elusive. We have previously shown that active FGFR2 (FGFR2-CA) contributes to increased tumor growth and that RUNX2 expression was high in hormone-independent mouse mammary carcinomas. To elucidate the interaction between FGFR2 and RUNX2 in human BrCa, we investigated their roles in tumor progression and treatment responsiveness. Increased FGFR2 activity resulted in higher RUNX2 expression, cell proliferation, and metastasis. In contrast, silencing FGFR2 reduced these parameters. Overexpression of RUNX2 in FGFR2-silenced cells rescued the inhibitory effects, promoting a more aggressive phenotype, even if compared with the wt RUNX2-transfected cells, which also had increased aggressiveness compared with naïve-transfected cells. RUNX2-overexpressing tumors were insensitive to endocrine- or FGFR inhibitor treatments. Notably, the CBFβ-RUNX complex inhibitor, AI-14-91, demonstrated great effectiveness in vitro. In a small cohort of luminal BrCa patients, nuclear RUNX2 expression was associated with tumor recurrence. Transcriptomic analysis strongly supported these data showing that patients with luminal carcinomas with high RUNX2 activity score have a worse progression-free interval than those with low RUNX2 activity. Our findings suggest a complex interplay between FGFR2 and RUNX2 in regulating tumor aggressiveness. This study underscores the significance of RUNX2 in luminal BrCa progression and posits RUNX2 as a promising therapeutic target and as a potential prognostic biomarker in luminal BrCa patients.

Continuing Cyclin-Dependent Kinase 4/6 Inhibitors Beyond Progression in Advanced Breast Cancer: A Meta-Analysis

Background: The use of cyclin-dependent kinase 4/6 inhibitors (CDK 4/6i) with endocrine therapy (ET) is a first-line standard treatment for hormone receptor-positive (ER+) Human Epidermal Growth factor Receptor-2-negative (HER2-) advanced breast cancer. The data supporting incorporation of CDK 4/6i + ET beyond progression are variable. Here, we report a pooled analysis of this strategy. Methods: A systematic review identified reports of both observational and clinical studies, which evaluated the continuation of CDK4/6i beyond progression. The mean overall response rate (ORR) and progression-free survival (PFS) weighted by the study sample size were calculated. Meta-regression comprising linear regression weighted by the sample size (mixed effects) was performed to explore the association between disease and treatment-related factors and the benefit from continuing CDK4/6i. Quantitative significance was assessed using the Burnand criteria. Results: Thirteen studies comprising 1530 patients were included. The median age was 58 years, 50.8% had visceral metastases, and 48% had ESR1 mutations; the median lines of prior therapies were 1 (range 1-5), and 96.3% received palbociclib as the initial CDK4/6i. Eight studies tested a CDK4/6i switch as the intervention. The median PFS was 5.3 months, and the ORR was 14%. In randomized studies, statistically significant differences were observed between CDK4/6i continuation and control, although it is uncertain whether the magnitude of the effect is clinically meaningful. Increasing age, lack of prior chemotherapy, no visceral metastasis or ESR1 mutations, and a switch to a non-palbociclib CDK4/6i were associated with better outcomes. Conclusion: Continuing a CDK 4/6i + ET beyond progression yields modest benefits. Switching CDK4/6i likely results in improved ORR and PFS. Continuing palbociclib beyond progression is likely ineffectual.

PROteolysis TArgeting Chimera (PROTAC) Estrogen Receptor Degraders for Treatment of Estrogen Receptor-Positive Advanced Breast Cancer

The estrogen receptor (ER) signaling pathway is a key driver of breast cancer, primarily through the activation of genes that promote tumor cell survival and growth. The recommended first-line treatment for ER-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer is endocrine therapy plus a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. However, most patients experience disease progression, and there is no clear standard of care in the second-line setting. Thus, novel treatments in the advanced setting are needed. In this narrative review, we describe the unique mechanisms of action of a new class of drugs called PROteolysis TArgeting Chimera (PROTAC) ER degraders. Unlike other ER-targeted therapies, these small molecules harness the body's primary intracellular natural protein disposal machinery, the ubiquitin-proteasome system, to directly induce ER degradation. Vepdegestrant (ARV-471) is the furthest advanced PROTAC ER degrader currently in clinical development. Preclinical data demonstrate increased tumor growth inhibition with vepdegestrant alone or in combination with CDK4/6 inhibitors compared with the selective ER degrader fulvestrant. In a first-in-human phase 1/2 clinical study, vepdegestrant administered orally as monotherapy or in combination with palbociclib showed promising clinical activity and a favorable safety profile in patients with heavily pretreated ER+/HER2- advanced breast cancer. Several other PROTAC ER degraders (AC699, ERD-3111, ERD-4001, and HP568) are in early development and have demonstrated activity in preclinical breast cancer models, with some recently entering clinical trials. The data highlight the potential for PROTAC ER degraders to be a new backbone therapy in breast cancer.

Impact of the Basic Mandatory Health Insurance "AMO-Tadamon" on Continuity of Care Among Breast Cancer Patients Treated at the Oncology Center of the CHU Mohammed VI in Tangier: A Mixed Longitudinal Cohort Study

Introduction

In Morocco, AMO-Tadamon is a basic mandatory health insurance scheme designed to ensure right to health for all. Implementation of this reform is advantageous for access to healthcare services. However, its impact on continuity of care needs to be assessed. In this study, we aimed to evaluate its impact on continuity of care for breast cancer patients at the Oncology Center of CHU Mohammed VI-Tangier between September 2022 and September 2023.

Methods

This was a mixed longitudinal cohort study. Follow-up information was collected over 13 months. December 1, 2022 was the index-event. Continuity of care was measured using "Bice-Boxerman Continuity of Care Index" and "Usual Provider Continuity" over three chronological sequences.

Results/Discussion

We recorded 74 cases in total, 16/74 were lost to follow-up (21.6%). Significant association (p=0.001; CI (0.01-0.04)) was observed between AMO-Tadamon generalization and continuity of care in our patients. For both indicators (UPC and COCI), mean continuity of care scores ranged from 0.25 to 0.75 over the three reference periods. This indicates a moderate overall continuity of care. During the first 4 months of this reform, significant positive associations were found between Therapy postponement and its implementation (p=0.003; CI (0.01--0.04)). Moreover, access to expensive drugs was significantly higher in the postgeneralization period (p=0.027; CI (0.01-0.04)).

Conclusion

Our study suggests a negative impact of this reform on patient care during the period of its generalization and a positive effect on access to expensive drugs after its generalization. A long-term follow-up study is planned. This will assess the impact of this reform on survival.

Expert Perspectives on Controversies and Critical Knowledge Gaps in Breast Cancer Management: Proceedings of the First Bridging the Gaps in Breast Cancer Symposium

PURPOSE

Breast cancer is the most common type of cancer for women in the United States and accounts for nearly 25% of all cancers and 16% of cancer deaths worldwide. New treatment options continue to emerge offering improved management options for patients with breast cancer. However, as these new treatments become available, clinicians are left with many questions regarding how to best utilize these treatments and improve outcomes for patients with breast cancer.

MATERIALS AND METHOD

The Bridging the Gaps in Breast Cancer panel was assembled to address challenges in the management of breast cancer. Bridging the Gaps in Breast Cancer co-chairs and session moderators identified areas of controversy and uncertainty in breast cancer management and were responsible for organizing the presentations and discussion with the expert panel of faculty throughout the meeting.

RESULTS

The Bridging the Gaps in Breast Cancer panel discussions are presented. Key critical knowledge gaps surrounding the evolving breast cancer treatment landscape identified include how to identify which patients will benefit the most from therapeutic intervention, the mechanism of resistance to newly approved therapies, which therapies may be safely omitted from a treatment regimen without harm to the patient, and the most important metric(s) in defining successful treatment in various stages and subtypes of breast cancer.

CONCLUSIONS

The treatment armamentarium for the management of breast cancer continues to grow and evolve. With those new treatment options, new questions continue to arise for clinicians. Future studies are needed to address these critical gaps in knowledge about how to best utilize treatments for improved patient outcomes.

Optimal extension time after initial endocrine therapy for postmenopausal hormone receptor-positive early-stage breast cancer: a systematic review and meta-analysis

BACKGROUND

The optimal duration of extended endocrine therapy (ET) for women with hormone receptor-positive (HR-positive) early-stage postmenopausal breast cancer remains uncertain. This meta-analysis systematically evaluated the optimal time to prolong aromatase inhibitors ( AIs) therapy for postmenopausal early stage breast cancer who received initial endocrine therapy.

METHODS

PubMed, Web of Science, Ovid, Scopus, EmBase, and Cochrane Library were searched for randomized controlled trials (RCTs) using keywords related to breast cancer, HR-positive, AIs, and tamoxifen (TAM). Disease-free survival (DFS) was used as the primary endpoint. Meta-analysis was performed using STATA 16.0 and Revman 5.4 statistical software. Hazard ratio (HR) with its corresponding 95% confidence intervals (CI) was used as an effective indicator to assess DFS, OS, and subgroups of extended ET. Relative ratio (RR) was used to assess adverse events.

RESULTS

The study included four RCTs involving 8,748 patients with HR-positive breast cancer. Pooled data showed an improvement in DFS when extending endocrine therapy from 5 to 7-8 years (HR = 0.82, 95% CI: 0.73 ~ 0.93), especially in patients with tumor size ≥ 2 cm (HR = 0.69, 95% CI: 0.49 ~ 0.98), estrogen receptor (ER) and progesterone receptor (PR) positive (HR = 0.77, 95% CI: 0.67 ~ 0.89), human epidermal growth factor receptor 2 (HER-2) positive or negative (HR = 0.85, 95% CI: 0.74 ~ 0.97; HR = 0.44, 95% CI: 0.22 ~ 0.89) and previous chemotherapy (HR = 0.80, 95% CI: 0.68 ~ 0.95). However, DFS has not improved with the extension from 7-8 to 10 years (HR = 0.97, 95% CI: 0.85 ~ 1.10). Furthermore, we found no significant difference in overall survival (OS), adverse events (AEs) analysis revealed a significant increase in the incidence of arthralgia, osteoporosis, bone fractures and asthenia after extended AIs.

CONCLUSIONS

The proportion of patients with breast cancer receiving ET extended beyond 5 years has increased, while the extension of AIs treatment from 5 to 7-8 years may be an option for high-risk patients with well-tolerated tumor size ≥ 2 cm, HR-positive, and previous chemotherapy. However, a variety of adverse events may accompany ET therapy, the identification of factors that may benefit breast cancer patients requires further randomized controlled studies.

PROSPERO REGISTRATION NUMBER

CRD42022335497.

A Canadian real-world, multi-center, prospective, observational study assessing the treatment duration, the treatment sequence, and the overall survival for patients treated with endocrine therapy ± targeted therapy in HR + HER2-negative advanced breast cancer

PURPOSE

Understanding real-world treatment patterns and their effectiveness in HR + HER2- advanced breast cancer (aBC) in Canadian patients.

PATIENT AND METHODS

This was a multi-center, observational, prospective cohort study including men and pre-/peri-/postmenopausal women with HR + HER2- aBC receiving endocrine therapy (ET) or ET + targeted therapy (ET + TT). The primary objective was duration of treatment (DOT) with ET and ET + TT. Sequence of therapies, treatment patterns, and Overall Survival (OS) were also evaluated.

RESULTS

DOT was prolonged in patients receiving ET + TT compared to ET (median DOT: ET + TT 397 days vs ET 192 days; Log-Rank test p value < .0001; HR = 0.66; 95% CI; 0.52, 0.85). An extended DOT was observed in ET + CDK4/6i subgroup when compared to ET (median DOT: ET + CDK4/6i 601 days vs ET 192 days; Log-Rank test p value < .0001). This increase was statistically significant irrespective of line of therapy at baseline (1L: median DOT: ET + CDK4/6i: 649 days vs ET: 217 days, p value =  < .0001; 2L: median DOT: ET + CDK4/6i: 487 days vs ET: 203 days, p value = 0.0013; 3L: median DOT: ET + CDK4/6i: 597 days vs ET: 143 days therapy: p value = 0.0006). ET alone and ET + CDK4/6i were the most frequently administered therapies in both 1st (ET alone: 43.5% and ET + CDK4/6i: 43.3%) and 2nd lines (ET alone: 36.3% and ET + CDK4/6i: 24.6%). Among patients who received at least one CDK4/6i in 1st, 2nd, or 3rd line, CDK4/6i were mostly administered in 1st line (61.9%) and 2nd line (38.5%).

CLINICALTRIALS

gov ID: NCT02753686; Registration Date:20-04-2016.

CONCLUSION

Results support current treatment recommendations of early introduction of CDK4/6i in HR + /HER2- aBC.

CDK4/6 inhibitors for metastatic breast cancer in routine clinical practice in Spain: survey of patterns of use and oncologists' perceptions

PURPOSE

To assess the use of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors in routine clinical practice in Spain, as well as the perceptions from oncologists.

METHODS

A survey was developed by nine oncologists, experts in breast cancer, practising in Spain. Survey responses were collected between July 2022 and April 2023.

RESULTS

Fifty-one survey responses were obtained. Most oncologists used CDK4/6 inhibitors in the first line. The first-line endocrine therapy most frequently used was an aromatase inhibitor (endocrine-sensitive disease) and fulvestrant (endocrine-resistant disease). CDK4/6 inhibitors were used for primary or secondary resistance, or visceral disease without visceral crisis. A lower-than-standard starting dose was considered (57% of respondents) for specific profiles. Strategies to manage toxicity included switching to another CDK4/6 inhibitor or delaying the next dose. CDK4/6 inhibitors were mostly considered to improve quality of life.

CONCLUSIONS

Use of CDK4/6 inhibitors in Spain follows current recommendations and aligns with the evidence.

Thymidine kinase 1 concentration and activity in metastatic breast cancer under CDK4/6 inhibitor therapy

We investigated whether TK1 concentration or activity in the blood, drawn at baseline and under therapy, might have value for therapy management in 110 hormone receptor-positive (HR+), HER2-negative (HER2-) metastatic breast cancer (mBC) patients treated with CDK4/6 inhibitors (CDK4/6i) and/or endocrine therapy (ET). TK1 concentration and activity were not significantly correlated with each other in matched samples. In the CDK4/6i cohort at baseline, high TK1 concentration and activity were significantly associated with a decreased PFS and primary resistance. Longitudinal sampling revealed a higher variability of TK1 concentration under therapy compared to TK1 activity that was reduced during therapy. Elevated TK1 activity after six months of CDK4/6i and an increase in TK1 concentration from baseline to six months under CDK4/6i significantly correlated with a decreased PFS. These results indicate a possible value of TK1 concentration and activity before and during CDK4/6i for HR+/HER2- mBC patients to guide treatment that warrants further investigation.

Clinician's guide: expert insights on the use of CDK4/6 inhibitors in patients with early breast cancer

The introduction of the cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors abemaciclib and ribociclib to the adjuvant setting marks a significant advancement in the treatment of hormone-receptor-positive, human epidermal growth factor receptor 2-negative early breast cancer (HR+, HER2- EBC). Despite significant strides in early detection and treatment, many patients continue to face the risk of disease recurrence, highlighting the need for more effective adjuvant therapies. These CDK4/6 inhibitors, combined with adjuvant endocrine therapy, have shown promising efficacy in reducing recurrence rates while maintaining a manageable safety profile, as evidenced by the monarchE and NATALEE trials. This paper explores the integration of adjuvant CDK4/6 inhibitors into clinical practice, focusing on disease-free survival and safety outcomes. Key considerations in selecting between abemaciclib and ribociclib are discussed, including patient risk profiles, efficacy and safety profiles, treatment duration, and individual patient preferences. In addition, we discuss managing adverse events to prevent premature discontinuation, with strategies that include dose holds, dose reductions, proactive symptom management, and patient education. The paper also highlights strategies to enhance patient medication adherence and the involvement of multidisciplinary care teams to support treatment delivery. As research continues to evolve, additional follow-ups of the monarchE and NATALEE trials and future trials will further refine patient selection and treatment sequencing, ultimately improving outcomes and enhancing the quality of life for patients with HR+, HER2- EBC.

Cost-effectiveness of sacituzumab govitecan for hormone receptor-positive human epidermal growth factor receptor 2-negative metastatic breast cancer based on the EVER-132-002 trial in China

BACKGROUND

The EVER-132-002 trial demonstrated the significant efficacy and manageable safety of sacituzumab govitecan in hormone receptor-positive human epidermal growth factor receptor 2-negative (HR + HER2-) metastatic breast cancer. This study evaluated the cost-effectiveness of sacituzumab govitecan compared with chemotherapy from the Chinese healthcare system perspective.

METHODS

A partitioned survival model at 21-day intervals over a 10-year time horizon was developed to evaluate the total cost, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER) at willingness-to-pay (WTP) threshold of 3 times gross domestic product per capita ($38,042.49 per QALY). Clinical data were extracted from the EVER-132-002 trial; direct medical costs and utility values were obtained from public bid-winning databases, local charges or published literature. To determine the model's robustness, scenario, one-way, two-way and probabilistic sensitivity analyses were performed.

RESULTS

Compared with chemotherapy, sacituzumab govitecan generated an additional cost of $91,273.72, with an additional QALY of 0.43, resulted in an ICER of $211,948.62 per QALY. Patient weight was the most influential parameter on base-case results, and variations in each parameter did not substantially alter the conclusion. Probabilistic sensitivity analysis demonstrated that the probability of sacituzumab govitecan to be cost-effective was zero at the WTP threshold of $38,042.49 per QALY. Scenario analysis indicated that sacituzumab govitecan would be cost-effective versus chemotherapy only if its cost was reduced by 83% ($202.65 per unit) or more.

CONCLUSIONS

Sacituzumab govitecan might not be cost-effective compared with chemotherapy in the treatment for HR + HER2- metastatic breast cancer in China.

Efficiency of Fulvestrant Monotherapy After CDK4/6 Inhibitor Exposure: Is This a Viable Choice?

Guidelines for the first-line treatment of Hormone Receptor-positive, HER2-negative advanced or recurrent breast cancer have shifted to combination therapies of a CDK4/6 inhibitor and endocrine therapy. However, determining an optimal subsequent therapy following CDK4/6 inhibitor progression remains challenging, especially for tumors lacking actionable mutations. Real-world data suggest that fulvestrant monotherapy is frequently selected in this post-CDK4/6 inhibitor setting. This review examines its therapeutic potential in this evolving landscape. A systematic literature search using PubMed and ClinicalTrials.gov identified 153 clinical trials published between 2017 and November 2024, from which ten studies met our strict inclusion criteria, focusing solely on fulvestrant monotherapy. These trials encompassed 1038 patients who had prior exposure to CDK4/6 inhibitors. The selected studies were categorized into three groups: monotherapy trials (EMERALD, SERENA-2, AMEERA-3, and ELAINE-1), combination therapy trials (CAPItello-291 and VERONICA), and CDK4/6 inhibitor rechallenge trials (post-MONARCH, PACE, PALMIRA, and MAINTAIN). The median progression-free survival for fulvestrant monotherapy was 3.18 months (range 1.9-5.3 months). Factors affecting the efficacy of fulvestrant monotherapy in second-line therapy include prior treatments, treatment duration, and genetic mutations. Given that the efficacy of fulvestrant was short-lived in the second or subsequent lines, participating in clinical trials is a vital option until a novel alternative treatment choice becomes available.

Phase I clinical trial to assess safety and efficacy of Oraxol, a novel oral paclitaxel chemotherapy agent, in patients with previously treated metastatic breast cancer

Oraxol, a novel oral paclitaxel chemotherapy agent, has emerged as a potential alternative for treating metastatic breast cancer (MBC). However, its safety and efficacy remain uncertain due to insufficient evidence supporting it. This open-label, single-arm, phase I trial was designed to assess the pharmacokinetics, safety, and preliminary antitumor activity of Oraxol in previously treated MBC. The primary objective was to investigate the pharmacokinetics of Oraxol, while secondary endpoints included assessing safety, tolerability, and antitumor activity. Twenty-four patients (median age, 53 years) were enrolled, and pharmacokinetic analysis showed consistent and reproducible absorption of Oraxol. Note that 96% patients experienced treatment-related adverse events (TRAEs) and no deaths attributed to TRAEs. The overall response rate was 34.8%, including 34.8% achieving partial response and 56.5% having stable disease. The median follow-up was 45.7 months, with median progression-free survival (PFS) of 3.41 months and median overall survival of 17.80 months. Notably, among patients with triple-negative breast cancer, the disease control rate was 100%, and the median PFS was 8.90 months, which notably exceeded the outcomes observed in other subtypes. Oraxol significantly alters metabolism and correlates with response and survival. In conclusion, Oraxol exhibited promising antitumor efficacy and manageable safety profiles in MBC patients.

Real-world quality-of-life of patients with HR+/HER2- advanced breast cancer treated with palbociclib plus endocrine therapy: EORTC QLQ-C30 results from POLARIS

PURPOSE

To evaluate patient-reported health-related quality-of-life (QoL) in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced/metastatic breast cancer (ABC) treated with palbociclib in the longitudinal real-world study, POLARIS.

METHODS

Data were prospectively collected from adult patients with HR+/HER2- ABC treated with palbociclib plus endocrine therapy (ET) in routine clinical practice. QoL was assessed with the European Organisation for Research and Treatment of Cancer Quality-of-Life Questionnaire-Core 30 (EORTC QLQ-C30) and reported at baseline and months 6, 12, and 18. Data were expressed as absolute scores at a given time and change from baseline for global QoL and functional/symptom scales. Global Heath Status (GHS)/QoL scores were also determined across 6 patient subgroup categories (e.g., age, visceral disease status). Additionally, the proportions of patients with scores below (functional scales) or above (symptom scales) EORTC-validated thresholds reflecting clinical importance of a health problem were determined.

RESULTS

Among patients treated with palbociclib plus ET (N = 1250) who completed questionnaires at any of the study timepoints, mean GHS/QoL scores at months 6 (69.3), 12 (70.1), and 18 (69.9) were higher than baseline (64.0). Similar trends were observed for functional and symptom scales. Mean GHS/QoL scores over time were consistent across the evaluated subgroups. Decreases in the proportions of patients with clinically important functional impairment/symptoms were observed for most functional/symptom scales from baseline through month 18.

CONCLUSION

Findings from this real-world study indicate patients with HR+/HER2- ABC treated with palbociclib plus ET maintain their QoL for at least 18 months.

CLINICAL TRIAL REGISTRATION

NCT03280303; registered 12 September 2017.

The Cost-Effectiveness of CDK4/6 Inhibitors in Treating HR+/HER2- Metastatic Breast Cancer Patients in the USA: When Non-medication Expenses are Considered

BACKGROUND AND OBJECTIVE

Cyclin-dependent kinase (CDK)4/6 inhibitors in combination with endocrine therapy (ET) significantly enhance progression-free survival and overall survival in patients diagnosed with HR+/HER2- metastatic breast cancer (MBC). However, they are highly expensive, and their economic impact has not been fully evaluated. This is a retrospective secondary analysis evaluating the cost effectiveness of these drugs, differentiating between medication-related and non-medication costs from a healthcare perspective.

METHODS

We identified 3879 patients diagnosed with MBC who received either CDK4/6i+ET (N = 2137) or ET alone (N = 1742) as first-line treatment between February 2015 and November 2021 using a USA-wide electronic health record-derived de-identified database. SEER-Medicare claims spending data were used to quantify monthly costs as a supplement to the database. Relevant costs included prescribed medications (ET and/or CDK4/6i) and overall other costs. The effectiveness was measured as progression-free duration in months. The incremental cost effectiveness ratio (ICER) analysis was conducted to examine the cost effectiveness of first-line CDK4/6i as compared with first-line ET alone.

RESULTS

For medication costs, CDK4/6i+ET (mean cost: $240,723.7; mean effect: 19.2 months of delayed progression) compared with ET alone (mean cost: $5159.7; mean effect: 16 months without progression) resulted in an ICER of $73,098 per month of delayed progression. For non-medication costs, CDK4/6i+ET (mean cost: $43,656.6) compared with ET alone (mean cost: $66,083.5) resulted in an ICER of - $7178 per month of delayed progression.

CONCLUSION

The cost of treating HR+/HER2- MBC is driven by the cost of CDK4/6i. Using CDK4/6i+ET reduces non-medication costs compared to ET alone, but these savings are offset by high CDK4/6i medication costs. Lowering the market cost of CDK4/6i or targeting those who can benefit the most could improve the cost effectiveness of CDK4/6i from Medicare perspective.

CDK4/6 inhibitor plus endocrine therapy for advanced breast cancer: results from a web-based survey in Japan

BACKGROUND

Though efforts have been made toward standardizing access to quality cancer care in Japan, there are still geographical and institutional disparities in the level of cancer care availability. We investigated the utilization of cyclin-dependent kinase 4/6 inhibitors plus endocrine therapy (CDK4/6i+ET) as first-line (1 L) treatment for hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC) in Japan.

RESEARCH DESIGN AND METHODS

This cross-sectional survey included physicians who had treated ≥3 1 L patients with HR+/HER2- ABC in the past year.

RESULTS

Of 41,695 physicians invited, 300 were included in the analysis. The mean percentage share of CDK4/6i+ET and ET monotherapy was 38.3% and 42.2%, respectively. Common challenges facing CDK4/6i+ET prescription were adverse reaction management, prohibitive cost, and a preference for ET monotherapy for treating elderly patients. Key solutions included reducing the burden of adverse reaction management, improving financial support, and preparing educational videos for medical staff.

CONCLUSIONS

The study concluded that CDK4/6i+ET is not well established as a 1 L option in Japan as of 2022. More effective ways of creating awareness and supportive tools are needed for CDK4/6i+ET to be adopted as standard of care in Japan.

TRIAL REGISTRATION NUMBER

UMIN000050760.

CARDIAC-STAR: prevalence of cardiovascular comorbidities in patients with HR + /HER2 - metastatic breast cancer

BACKGROUND

Cardiovascular (CV) comorbidities and concurrent medications with risk of heart rate-corrected QT interval (QTc) prolongation can impact treatment decisions and safety discussions for patients with breast cancer. However, limited data are available regarding their prevalence in patients with HR + /HER2- metastatic breast cancer (mBC). We evaluated the prevalence of CV comorbidities, the use of concurrent medications with risk of QTc prolongation, and treatment patterns in patients with newly diagnosed HR + /HER2 - mBC.

METHODS

This retrospective analysis utilized claims data from Merative™ Marketscan® Commercial and Medicare databases. Claims-based algorithms identified patients with newly diagnosed HR + /HER2- mBC between January 2016 and December 2022. The index date was defined as the first date of an mBC claim during this period. For each patient, data on pre-existing CV comorbidities and first-line treatments were captured for 12 months before and 6 months after the index date, respectively.

RESULTS

A total of 6525 patients with newly diagnosed HR + /HER2 - mBC were identified. At mBC diagnosis, 61.7% of patients had ≥ 1 CV comorbidity. Of patients with CV comorbidities, 22.5% and 30.6% took 1 or ≥ 2 medications, respectively, with risk of QTc prolongation. First-line use of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors increased from 22.1% of patients with CV comorbidities diagnosed in 2016-2017 to 31.5% of those diagnosed in 2018-2022.

CONCLUSIONS

We found that CV comorbidities and use of medications with risk of QTc prolongation were common in patients with newly diagnosed HR + /HER2 - mBC. These factors should inform treatment decision-making (including CDK4/6 inhibitor selection), safety discussions with patients, and CV monitoring.

Datopotamab Deruxtecan Versus Chemotherapy in Previously Treated Inoperable/Metastatic Hormone Receptor-Positive Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer: Primary Results From TROPION-Breast01

PURPOSE

The global, phase 3, open-label, randomized TROPION-Breast01 study assessed the trophoblast cell surface antigen 2-directed antibody-drug conjugate datopotamab deruxtecan (Dato-DXd) versus investigator's choice of chemotherapy (ICC) in hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer.

METHODS

Adult patients with inoperable/metastatic HR+/HER2‒ breast cancer, who had disease progression on endocrine therapy, for whom endocrine therapy was unsuitable, and had received one to two previous lines of chemotherapy in the inoperable/metastatic setting, were randomly assigned 1:1 to Dato-DXd (6 mg/kg once every 3 weeks) or ICC (eribulin/vinorelbine/capecitabine/gemcitabine). Dual primary end points were progression-free survival (PFS) by blinded independent central review (BICR) and overall survival (OS).

RESULTS

Patients were randomly assigned to Dato-DXd (n = 365) or ICC (n = 367). Dato-DXd significantly reduced the risk of progression or death versus ICC (PFS by BICR hazard ratio [HR], 0.63 [95% CI, 0.52 to 0.76]; P < .0001). Consistent PFS benefit was observed across subgroups. Although OS data were not mature, a trend favoring Dato-DXd was observed (HR, 0.84 [95% CI, 0.62 to 1.14]). The rate of grade ≥3 treatment-related adverse events (TRAEs) with Dato-DXd was lower than ICC (20.8% v 44.7%). The most common TRAEs (any grade; grade ≥3) were nausea (51.1%; 1.4%) and stomatitis (50%; 6.4%) with Dato-DXd and neutropenia (grouped term, 42.5%; 30.8%) with ICC.

CONCLUSION

Patients receiving Dato-DXd had statistically significant and clinically meaningful improvement in PFS and a favorable and manageable safety profile, compared with ICC. Results support Dato-DXd as a novel treatment option for patients with inoperable/metastatic HR+/HER2‒ breast cancer who have received one to two previous lines of chemotherapy in this setting.

(E)-1-(3-(3-Hydroxy-4-Methoxyphenyl)-1-(3,4,5-Trimethoxyphenyl)allyl)-1H-1,2,4-Triazole and Related Compounds: Their Synthesis and Biological Evaluation as Novel Antimitotic Agents Targeting Breast Cancer

Background/Objectives: The synthesis of (E)-1-(1,3-diphenylallyl)-1H-1,2,4-triazoles and related compounds as anti-mitotic agents with activity in breast cancer was investigated. These compounds were designed as hybrids of the microtubule-targeting chalcones, indanones, and the aromatase inhibitor letrozole. Methods: A panel of 29 compounds was synthesized and examined by a preliminary screening in estrogen receptor (ER) and progesterone receptor (PR)-positive MCF-7 breast cancer cells together with cell cycle analysis and tubulin polymerization inhibition. Results: (E)-5-(3-(1H-1,2,4-triazol-1-yl)-3-(3,4,5-trimethoxyphenyl)prop-1-en-1-yl)-2-methoxyphenol 22b was identified as a potent antiproliferative compound with an IC50 value of 0.39 mM in MCF-7 breast cancer cells, 0.77 mM in triple-negative MDA-MB-231 breast cancer cells, and 0.37 mM in leukemia HL-60 cells. In addition, compound 22b demonstrated potent activity in the sub-micromolar range against the NCI 60 cancer cell line panel including prostate, melanoma, colon, leukemia, and non-small cell lung cancers. G2/M phase cell cycle arrest and the induction of apoptosis in MCF-7 cells together with inhibition of tubulin polymerization were demonstrated. Immunofluorescence studies confirmed that compound 22b targeted tubulin in MCF-7 cells, while computational docking studies predicted binding conformations for 22b in the colchicine binding site of tubulin. Compound 22b also selectively inhibited aromatase. Conclusions: Based on the results obtained, these novel compounds are suitable candidates for further investigation as antiproliferative microtubule-targeting agents for breast cancer.

Endocrine treatment mechanisms in triple-positive breast cancer: from targeted therapies to advances in precision medicine

Triple-positive breast cancer (TPBC), defined by the co-expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), poses unique therapeutic challenges due to complex signaling interactions and resulting treatment resistance. This review summarizes key findings on the molecular mechanisms and cross-talk among ER, PR, and HER2 pathways, which drive tumor proliferation and resistance to conventional therapies. Current strategies in TPBC treatment, including endocrine and HER2-targeted therapies, are explored alongside emerging approaches such as immunotherapy and CRISPR/Cas9 gene editing. Additionally, we discuss the tumor microenvironment (TME) and its role in treatment resistance, highlighting promising avenues for intervention through combination therapies and predictive biomarkers. By addressing these interdependent pathways and optimizing therapeutic strategies, precision medicine holds significant potential for improving TPBC patient outcomes and advancing individualized cancer care.

Efficacy and safety of antibody-drug conjugates in pretreated HER2-low metastatic breast cancer: A systematic review and network meta-analysis

INTRODUCTION

Antibody-drug conjugates (ADCs) trastuzumab-deruxtecan (T-DXd) and sacituzumab-govitecan (SG) provided significant progression-free survival (PFS) and overall survival (OS) improvements over chemotherapy (CT) in pretreated hormone receptor-positive (HR+) and triple-negative (TN)/HER2-low metastatic breast cancer (MBC). However, no direct comparison between the two exists, nor with the more recent datopotamab-deruxtecan (Dato-DXd).

METHODS

We conducted a network meta-analysis (NMA) to compare efficacy and safety of T-DXd and SG in CT-pretreated HR+ and TN/HER2-low MBC and assess their benefit over standard CT, exploring also a comparison with Dato-DXd. Hazard ratios (HRs) with 95 % confidence intervals (CI) were calculated for PFS/OS. P-score was used for treatment ranking.

RESULTS

Three RCTs (956 patients) were included in the primary analysis and 5 (1,445) in the exploratory NMA with Dato-DXd. In HR+/HER2-low, T-DXd showed no significant difference in PFS and OS when compared to SG. Similarly, in TN/HER2-low, PFS and OS did not differ significantly between the two ADCs. The P-score analysis favored T-DXd over SG in HR+/HER2-low in PFS (0.90 vs. 0.60) and OS (0.89 vs. 0.60). SG was favored over T-DXd in OS in TN/HER2-low (0.80 vs. 0.69). Similar results were obtained for HR+ MBC when including Dato-Dxd, which showed the worst performance, while T-DXd was the only ADC significantly outperforming CT in OS. The ADCs showed significantly better PFS and OS than CT in HR+/HER2-low and TN/HER2-low (all p < 0.001). SG had higher rates of neutropenia, diarrhea and alopecia vs. T-DXd, which showed more thrombocytopenia, fatigue and nausea. Pneumonitis and cardiotoxicity were typically T-DXd-related, and T-DXd showed more toxicity-related discontinuations.

CONCLUSIONS

Similar efficacy with T-DXd and SG in HER2-low MBC was observed, regardless of HR status. Safety profile, local drug-approval criteria and guidelines, patients' preferences and overall quality of evidence should ultimately guide therapeutic decision-making. Dato-DXd role remains uncertain.

Safety and pharmacokinetics of vepdegestrant in Japanese patients with ER+ advanced breast cancer: a phase 1 study

BACKGROUND

Vepdegestrant (ARV-471) is an oral PROteolysis TArgeting Chimera (PROTAC) estrogen receptor (ER) degrader.

METHODS

This phase 1 study (NCT05463952) investigated safety, pharmacokinetics, and antitumor activity of vepdegestrant in Japanese patients with ER-positive (ER+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer at the 200-mg once daily (QD) recommended phase 3 dose. Eligible patients had ER+/HER2- advanced breast cancer resistant to standard therapy, with no standard therapy available, or had received two or more prior endocrine therapies in any setting. The primary endpoint was dose-limiting toxicities (DLTs) in cycle 1; secondary endpoints included safety, pharmacokinetics, and antitumor activity.

RESULTS

Six female patients (median age, 58 [range: 47-62] years) were treated. For advanced disease, three (50.0%) patients received three or more prior regimens and five (83.3%) patients received prior cyclin-dependent kinase 4/6 inhibitors. At data cutoff, median treatment duration was 9.8 (range: 6-28) weeks; two patients remained on treatment. No DLTs were observed. Four (66.7%) patients experienced adverse events; none led to dose reduction or discontinuation. Four (66.7%) patients had treatment-related adverse events; all were grade 1 except anemia (grade 2). Geometric mean maximum plasma concentration and 24-h area under the plasma concentration-time curve of vepdegestrant were 630.9 ng/mL and 10,400 ng∙hr/mL after a single dose and 1056 ng/mL and 18,310 ng∙hr/mL after multiple doses. Two (33.3%) patients demonstrated stable disease at week 24.

CONCLUSION

Vepdegestrant 200 mg QD was well tolerated in Japanese patients with ER+/HER2- advanced breast cancer with no notable differences in pharmacokinetics from Western patients.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT05463952 (date of registration: July 19, 2022).

Association between cyclin-dependent kinase 4/6 inhibitors and nephrotoxicity in patients with breast cancer: A Systematic Review and meta-analysis

Nephrotoxic adverse events (AEs) have been observed in patients with breast cancer receiving cyclin-dependent kinase (CDK) 4/6 inhibitors. This study aimed to evaluate the risk of nephrotoxicity associated with these inhibitors through a meta-analysis of 17 randomized controlled trials involving 19,638 patients. The results indicate a significant increase in all-grade nephrotoxic AEs, including elevated blood creatinine levels, acute kidney injury, and renal impairment (RR = 3.12, 95% CI [2.11, 4.63]). The incidence of grade 3 or higher nephrotoxicity was also more prevalent among treated patients (RR = 3.12, 95% CI [1.74, 5.58]). Subgroup analyses revealed varying risks among 4 different CDK 4/6 inhibitors. Furthermore, analysis of FDA Adverse Event Reporting System data corroborated these findings, emphasizing the occurrence of nephrotoxicity in real-world settings. Clinicians should remain vigilant in monitoring renal function indicators when prescribing CDK4/6 inhibitors.

ChatGPT's Agreement with the Recommendations from the 18th St. Gallen International Consensus Conference on the Treatment of Early Breast Cancer

Breast cancer is the most common cancer in women worldwide [...].

First-Line (1L) Treatment Decision Patterns and Survival of Hormone Receptor (HR)-Positive/HER2-Negative Advanced Breast Cancer (ABC) Patients in a Latin American (LATAM) Public Institution

Advanced breast cancer is an incurable disease, with a median overall survival of 3 years, including in countries without access problems. Although chemotherapy is reserved in some cases, it is still used in many countries as a first-line therapy. The aim of our study is to evaluate the first-line treatment choices and the factors that influence therapeutic decisions. A retrospective analysis was conducted of hormone receptor (+)/HER2 (-) advanced breast cancer patients classified into three groups according to the first-line and second-line treatment received: endocrine therapy-chemotherapy, endocrine therapy-endocrine therapy and chemotherapy-endocrine therapy. Additionally, we explored the overall survival of sequencing therapy groups. First-line chemotherapy was chosen in 34% of patients. Also, around 60% of our patients met the "aggressive disease" criteria from the RIGHT Choice trial, justifying the use of chemotherapy in a population with poor prognosis. Furthermore, de novo and progressive disease were prognostic factors that influenced the use of chemotherapy as a first-line treatment. Regarding overall survival, the sequencing treatment groups in this trial saw an increase in survival compared with patients of the MONALEESA trials (endocrine therapy alone arms). No significant differences in progression-free survival or overall survival were found in the treatment sequencing groups. There was a higher use of chemotherapy as a first-line therapy, with de novo and "aggressive disease" criteria being the main factors to influence the decision.

Rare Breast Cancers Review

BACKGROUND/OBJECTIVES

Breast cancer is one of the most common malignancies in women, with rare subtypes presenting unique clinical challenges. This review provides a comprehensive analysis of rare breast cancers, including both epithelial and non-epithelial subtypes, and explores their epidemiology, pathology, prognosis, and treatment approaches.

METHODS

A systematic review was conducted focusing on recent advancements in the treatment of rare breast cancer subtypes. Articles were selected based on criteria emphasizing studies from the past five years, with older foundational studies included where necessary. The analysis incorporated molecular profiling, clinical trials, and advancements in targeted and immunotherapies, where possible.

RESULTS

Rare epithelial subtypes, such as tubular, mucinous, and medullary carcinomas, demonstrate distinct clinical and pathological features, with generally favorable prognoses compared to invasive ductal carcinoma (IDC). Non-epithelial cancers, including sarcomas and primary breast lymphomas, require individualized treatment due to aggressive behavior and poor prognosis in certain cases. Recent advancements in targeted therapies (e.g., HER2 inhibitors, PI3K inhibitors, and PARP inhibitors) and immunotherapies (e.g., PD-1 inhibitors) have shown promise in improving outcomes for specific molecularly characterized subtypes.

CONCLUSIONS

While the management of common breast cancers has become increasingly sophisticated, rare subtypes continue to pose challenges due to limited research and small patient populations. Advances in molecular profiling and next-generation sequencing are pivotal in identifying actionable mutations and expanding personalized treatment options. Future research should focus on clinical trials and collaborative efforts to refine treatment strategies and improve outcomes for these rare subtypes.

Trastuzumab Deruxtecan after Endocrine Therapy in Metastatic Breast Cancer

BACKGROUND

Outcomes in patients with hormone receptor-positive metastatic breast cancer worsen after one or more lines of endocrine-based therapy. Trastuzumab deruxtecan has shown efficacy in patients with metastatic breast cancer with low expression of human epidermal growth factor receptor 2 (HER2) after previous chemotherapy.

METHODS

We conducted a phase 3, multicenter, open-label trial involving patients with hormone receptor-positive metastatic breast cancer with low HER2 expression (a score of 1+ or 2+ on immunohistochemical [IHC] analysis and negative results on in situ hybridization) or ultralow HER2 expression (IHC 0 with membrane staining) who had received one or more lines of endocrine-based therapy and no previous chemotherapy for metastatic breast cancer. Patients were randomly assigned in a 1:1 ratio to receive trastuzumab deruxtecan or the physician's choice of chemotherapy. The primary end point was progression-free survival (according to blinded independent central review) among the patients with HER2-low disease. Secondary end points included progression-free survival among all the patients who had undergone randomization, overall survival, and safety.

RESULTS

Of the 866 patients who underwent randomization, 713 had HER2-low disease, and 153 had HER2-ultralow disease. Among the patients with HER2-low disease, the median progression-free survival was 13.2 months (95% confidence interval [CI], 11.4 to 15.2) in the trastuzumab deruxtecan group and 8.1 months (95% CI, 7.0 to 9.0) in the chemotherapy group (hazard ratio for disease progression or death, 0.62; 95% CI, 0.52 to 0.75; P<0.001); the results were consistent in the exploratory HER2-ultralow population. Data for overall survival were immature. Adverse events of grade 3 or higher occurred in 52.8% of the patients in the trastuzumab deruxtecan group and in 44.4% of those in the chemotherapy group. Adjudicated interstitial lung disease or pneumonitis occurred in 49 patients (11.3%; three events were grade 5 in severity) and in 1 patient (0.2%; grade 2), respectively.

CONCLUSIONS

Among patients with hormone receptor-positive, HER2-low or HER2-ultralow metastatic breast cancer who had received one or more lines of endocrine-based therapy, treatment with trastuzumab deruxtecan resulted in longer progression-free survival than chemotherapy. No new safety signals were identified. (Funded by AstraZeneca and Daiichi Sankyo; DESTINY-Breast06 ClinicalTrials.gov number, NCT04494425.).

Molecular Profiling of Endocrine Resistance in HR+/HER2-Metastatic Breast Cancer: Insights from Extracellular Vesicles-Derived DNA and ctDNA in Liquid Biopsies

Standard treatments in hormone receptor-positive (HR+)/HER2-metastatic breast cancer (mBC) typically involve endocrine therapy (ET) combined with CDK4/6 inhibitors, yet resistance to ET remains a persistent challenge in advanced cases. A deeper knowledge of the use of liquid biopsy is crucial for the implementation of precision medicine in mBC with real-time treatment guidance. Our study assesses the prognostic value of PIK3CA and ESR1 mutations in DNA derived from extracellular vesicles (EV-DNA) in longitudinal plasma from 59 HR+/HER2-mBC patients previously exposed to aromatase inhibitors, with a comparative analysis against circulating tumor DNA (ctDNA). Mutations were evaluated by digital PCR. PIK3CA and ESR1 mutations were found in 22 and 25% of patients. Baseline ESR1 mutations in EV-DNA were associated with shorter progression-free survival (PFS) across the cohort, with the Y537S mutation showing a particularly strong impact on the outcome of fulvestrant-treated patients. In contrast, PIK3CA mutations in EV-DNA did not significantly correlate with PFS, whereas in ctDNA, they were linked to poor outcomes. Altogether, this study positions EV-DNA as a valuable biomarker alongside ctDNA, enriching the understanding of different analytes in liquid biopsy and supporting strategies for HR+/HER2-mBC in precision oncology.

A Preoperative Window-of-Opportunity Study of Oral SERD, Imlunestrant, in Newly Diagnosed ER-Positive, HER2-Negative Early Breast Cancer: Results from the EMBER-2 Study

PURPOSE

Imlunestrant is an oral selective estrogen receptor degrader with favorable safety and preliminary efficacy in patients with advanced breast cancer. Pharmacodynamic (PD) biomarker data can optimize drug dosing; in this study, we present PD data from the EMBER-2 study.

PATIENTS AND METHODS

Postmenopausal women with untreated, operable estrogen receptor (ER)-positive, HER2-negative early breast cancer were randomized to 400 versus 800 mg of imlunestrant daily for ∼2 weeks before surgery. A single arm study tested a daily dose of 200 mg. PD biomarker changes (ER, progesterone receptor, Ki-67 by IHC, and mRNA expression of ER-related genes) were evaluated in paired tumor samples (pre-/posttreatment). Safety and pharmacokinetics were also assessed.

RESULTS

Among evaluable paired samples (n = 75), PD profiles demonstrated consistent ER targeting between 400- and 800-mg doses, with less toxicity at the 400-mg dose. Although inducing the lowest rate of complete cell-cycle arrest, PD and pharmacokinetic results were similar for the 200-mg dose.

CONCLUSIONS

EMBER-2 combined with existing phase I data has identified 400 mg as the optimal imlunestrant dose.

Sacituzumab govitecan in HR+HER2- metastatic breast cancer: the randomized phase 3 EVER-132-002 trial

Sacituzumab govitecan (SG) significantly improved progression-free survival (PFS) and overall survival (OS) versus chemotherapy in hormone receptor-positive human epidermal growth factor receptor 2-negative (HR+HER2-) metastatic breast cancer (mBC) in the global TROPiCS-02 study. TROPiCS-02 enrolled few Asian patients. Here we report results of SG in Asian patients with HR+HER2- mBC from the EVER-132-002 study. Patients were randomized to SG (n = 166) or chemotherapy (n = 165). The primary endpoint was met: PFS was improved with SG versus chemotherapy (hazard ratio of 0.67, 95% confidence interval 0.52-0.87; P = 0.0028; median 4.3 versus 4.2 months). OS also improved with SG versus chemotherapy (hazard ratio of 0.64, 95% confidence interval 0.47-0.88; P = 0.0061; median 21.0 versus 15.3 months). The most common grade ≥3 treatment-emergent adverse events were neutropenia, leukopenia and anemia. SG demonstrated significant and clinically meaningful improvement in PFS and OS versus chemotherapy, with a manageable safety profile consistent with prior studies. SG represents a promising treatment option for Asian patients with HR+HER2- mBC (ClinicalTrials.gov identifier no. NCT04639986 ).

Using bioinformatics and artificial intelligence to map the cyclin-dependent kinase 4/6 inhibitor biomarker landscape in breast cancer

A cyclin-dependent kinase 4/6 (CDK4/6) inhibitor combined with endocrine therapy is the standard-of-care for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer. However, not all patients respond to the treatment, resistance often occurs and efficacy outcomes from early breast cancer trials have been mixed. To identify biomarkers associated with CDK4/6 inhibitor response or resistance, we combined bioinformatic-database analyses, artificial intelligence-assisted literature review, and manual literature review (Embase and OVID Medline; search window: January 2012-October 2022) to compile data to comprehensively describe the CDK4/6 inhibitor biomarker landscape. Based on these results, and validation by external experts, we identified 15 biomarkers of clinical importance (AR , AURKA, ERBB2, ESR1, CCNE1, CDKN1A/B, CDK2, CDK6, CDK7, CDK9, FGFR1/2, MYC, PIK3CA/AKT, RB1 and STAT3) that could guide future breast cancer research.

Neutrophil-to-lymphocyte ratio at the end of treatment with CDK4/6 inhibitors is an independent prognostic factor for ER-positive HER2-negative advanced breast cancer

PURPOSE

The aim of this study was to elucidate the clinical significance of peripheral blood biomarkers, including absolute lymphocyte count (ALC) and neutrophil-to-lymphocyte ratio (NLR), at the end of treatment (EOT) with CDK4/6 inhibitors abemaciclib and palbociclib in patients with estrogen receptor-positive human epidermal growth factor receptor 2-negative advanced breast cancer.

METHODS

We included 67 patients treated with fulvestrant plus abemaciclib or palbociclib. Overall survival (OS) since the EOT with CDK/4/6 inhibitors was compared in relation to the levels of ALC and NLR. The cut-off values of ALC and NLR were set at 1000/μL and 3, respectively.

RESULTS

Patients with a high ALC at EOT showed significantly longer OS than those with a low ALC (p = 0.0358). Moreover, patients with a low NLR at EOT showed significantly longer OS than those with a high NLR at EOT (p = 0.0044). Looking at the changes of ALC and NLR between baseline and the EOT, patients with a high ALC both at baseline and at the EOT showed significantly longer OS than others (p = 0.0201). Similarly, patients with a low NLR both at baseline and at the EOT showed significantly longer OS after EOT than others (p = 0.0136). Multivariable analysis revealed that the NLR at EOT (low vs. high) and changes in NLR (low at baseline to low at EOT vs. others) were significant and independent prognostic factors for OS after EOT (p = 0.0337, p = 0.0039, respectively).

CONCLUSION

NLR at EOT with CDK4/6 inhibitors is a significant and independent prognostic marker for patients with ER-positive HER2-negative advanced breast cancer.

Evaluation of CDK4/6 inhibitors in first-line in symptomatic and asymptomatic patients with metastatic breast cancer

BACKGROUND

This study aimed to compare the efficacy of CDK4/6 inhibitors plus endocrine therapy in two groups of patients with HR-positive/HER2-negative metastatic breast cancer: those with symptomatic, high tumor burden disease and those with asymptomatic disease.

DESIGN AND METHODS

This retrospective study included 193 patients who received either ribociclib or palbociclib in combination with first-line ET. Patients were divided into symptomatic and asymptomatic groups and compared regarding baseline characteristics and progression-free survivals (PFS).

RESULTS

Symptomatic patients had a significantly shorter mPFS than asymptomatic patients (22.7 months vs. 35.0 months, p = 0.009). Among symptomatic patients, those treated with ribociclib had a longer mPFS than those treated with palbociclib (28.26 months vs. 17.18 months, p = 0.021). Multivariate analysis identified the symptomatic disease and liver metastasis as independent predictors of shorter mPFS (HR; 1.835, 95% CI; 1.146-2.939 and HR; 2.433, 95% CI; 1.329-4.454, respectively).

CONCLUSION

Our analysis revealed that although symptomatic individuals who underwent CDK4/6 inhibitor plus ET experienced a significant reduction in mPFS durations compared to asymptomatic patients, the 22-month mPFS indicated that CDK4/6 inhibitor plus ET is an effective treatment option.

Patient with hormone receptor‑positive Her2‑negative metastatic breast cancer with visceral crisis with good response to abemaciclib and letrozole: A case report and review of the literature

Combined chemotherapy is typically the preferred treatment for patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC) experiencing a visceral crisis. However, the emergence of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) has introduced a potential alternative: The combination of CDK4/6i with endocrine therapy (ET). The present study reported a case of HR+/HER2-MBC with extensive liver and bone metastases who responded well to abemaciclib and letrozole. The patient achieved a rapid partial response and continuous clinical stabilization and the progression-free survival of this patient reaches 30 months and counting. Furthermore, the side effects were manageable and no dose reductions were necessary during treatment. These findings suggest that the combination of CDK4/6i and ET in the treatment of HR+/HER2-advanced breast cancer cannot be underestimated.

Phase I/Ib Trial of Inavolisib Plus Palbociclib and Endocrine Therapy for PIK3CA-Mutated, Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced or Metastatic Breast Cancer

PURPOSE

To investigate the safety, tolerability, pharmacokinetics (PK), and preliminary antitumor activity of inavolisib, a potent and selective small-molecule inhibitor of p110α that promotes the degradation of mutated p110α, in combination with palbociclib and endocrine therapy (ET), in a phase I/Ib study in patients with PIK3CA-mutated, hormone receptor-positive/human epidermal growth factor receptor 2-negative locally advanced/metastatic breast cancer (ClinicalTrials.gov identifier: NCT03006172).

METHODS

Women ≥18 years of age received inavolisib, palbociclib, and letrozole (Inavo + Palbo + Letro arm) or fulvestrant (Inavo + Palbo + Fulv arm) until unacceptable toxicity or disease progression. The primary objective was to evaluate safety or tolerability.

RESULTS

Fifty-three patients were included, 33 in the Inavo + Palbo + Letro arm and 20 in the Inavo + Palbo + Fulv arm. Median duration of inavolisib treatment was 15.7 and 20.8 months (cutoff: March 27, 2023), respectively. Treatment-related adverse events (TRAEs) occurred in all patients; the most frequent were stomatitis, hyperglycemia, and diarrhea; grade ≥3 any TRAE rates were 87.9% and 85.0%; 6.1% and 10.0% discontinued any treatment due to TRAEs in the Inavo + Palbo + Letro and Inavo + Palbo + Fulv arms, respectively. No PK drug-drug interactions (DDIs) were observed among the study treatments when administered. Confirmed objective response rates were 52.0% and 40.0% in patients with measurable disease, and median progression-free survival was 23.3 and 35.0 months in the Inavo + Palbo + Letro and Inavo + Palbo + Fulv arms, respectively. Available paired pre- and on-treatment tumor tissue and circulating tumor DNA analyses confirmed the effects of study treatment on pharmacodynamic and pathophysiologic biomarkers of response.

CONCLUSION

Inavolisib plus palbociclib and ET demonstrated a manageable safety profile, lack of DDIs, and promising preliminary antitumor activity.

First- vs second-line CDK 4/6 inhibitor use for patients with hormone receptor positive, human epidermal growth-factor receptor-2 negative, metastatic breast cancer in the real world setting

PURPOSE

To compare CDK4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) in the first- versus second-line setting for treatment of hormone receptor positive (HR+), HER2 negative, metastatic breast cancer (MBC) using real-world evidence.

METHODS

Patients with HR+, HER2 negative MBC, diagnosed between 2/3/2015 and 11/2/2021 and having ≥ 3 months follow-up were identified from the nationwide electronic health record-derived Flatiron Health de-identified database. Treatment cohorts included: (1) first-line ET with a CDK 4/6i (1st-line CDK4/6i) versus (2) first-line ET alone followed by second-line ET with a CDK4/6i (2nd-line CDK4/6i). Differences in baseline characteristics were tested using chi-square tests and two-sample t-tests. Time to third-line therapy, time to start of chemotherapy, and overall survival were compared using Kaplan-Maier method.

RESULTS

The analysis included 2771 patients (2170 1st-line CDK4/6i and 601 2nd-line CDK4/6i). Patients receiving 1st-line CDK4/6i were younger (75% vs 68% < 75 years old, p = 0.0001), less likely uninsured or not having insurance status documented (10% vs. 13%, p = 0.04), of better performance status (50% vs 43% with ECOG 0, p = 0.03), and more likely to have de novo MBC (36% vs. 24%, p < 0.001). Time to third-line therapy (49 vs 22 months, p < 0.001) and time to chemotherapy (68 vs 41 months, p < 0.001) were longer in those receiving first-line CDK4/6i. Overall survival (54 vs 49 months, p = 0.33) was similar between groups.

CONCLUSION

Use of CDK4/6i with first-, vs second-, line ET was associated with longer time to receipt of 3rd-line therapy and longer time to receipt of chemotherapy.

Hormones as a double-edged sword: the role of hormones in cancer progression and the potential of targeted hormone therapies

Cancer remains a significant cause of mortality in the world, with increasing prevalence worldwide. There are numerous treatments ranging from surgery to chemotherapy and radiotherapy, but since cancer is a heterogeneous disease, only few patients possibly respond to treatments. However, it opens a huge space for the advent of targeted therapies such as hormone therapy, immunotherapy, and target-specific drugs. Hormonal therapy using hormone agonists/antagonists or hormone receptor inhibitors-called the next-generation hormonal agents-hits distinct hormonal pathways that are involved in breast, prostate and ovarian cancer. Preliminary results show that through combination of drugs, it is possible that the synergistic effects may actually lead to better survival than with the use of single drugs. With manageable adverse effects, hormonal therapy offers much hope for treatment of this rather challenging malignancy of the hormone-sensitive cancers, especially in combination with other treatments.

Clinical characterization, prognostic, and predictive values of HER2-low in patients with early breast cancer in the PALLAS trial (ABCSG-42/AFT-05/BIG-14-13/PrE0109)

BACKGROUND

Bidirectional crosstalk between HER2 and estrogen receptor (ER) pathways may influence outcomes and the efficacy of endocrine therapy (ET). Low HER2 expression levels (HER2-low) have emerged as a predictive biomarker in patients with breast cancer (BC).

METHODS

PALLAS is an open, international, phase 3 study evaluating the addition of palbociclib for 2 years to adjuvant ET in patients with stage II-III ER-positive/HER2-negative BC. To assess the impact of HER2 expression on patient outcomes in the phase III PALLAS trial, we analyzed (1) the association between rate of HER2-low with demographic and clinicopathological parameters, (2) the prognostic value of HER2-low status on invasive disease-free survival (iDFS), distant relapse-free survival (DRFS), and overall survival (OS) and (3) HER2 expression's value as a predictive biomarker of response to palbociclib. HER2-low was defined as HER2 immunohistochemistry (IHC) 1 + or IHC 2 + with negative in situ hybridization (ISH). All pathologic evaluation was performed locally. Prognostic and predictive power of HER2 were assessed with Cox models.

RESULTS

From the original PALLAS intention-to-treat population (N = 5753), 5304 patients (92.2%) were included in this analysis. Among these, 2254 patients (42.5%) were classified as having HER2 IHC 0 (HER2-0), and 3050 (57.5%) as having HER2-low disease (1838 with IHC 1 + and 1212 with IHC 2 +). Median follow-up was 59.8 months. HER2-low prevalence varied significantly across 21 participating countries (range 16.7% to 75.6%; p < 0.001) and was more frequent in patients enrolled in North America (63.1%) than in Europe (53.4%) or other regions (53.4%) (p < 0.001). HER2 status was not significantly associated with iDFS in a multivariable Cox model (hazard ratio 0.93, 95% confidence interval 0.81 - 1.06). No significant interaction was observed between treatment arm and HER2 status for iDFS (p = 0.43). Similar results were obtained for DRFS and OS.

CONCLUSIONS

In this large, prospective, global patient cohort, no differences were observed in clinical parameters, prognosis, or differential benefit from palbociclib between HER2-0 and HER2-low tumors. Significant geographic variability was observed in the prevalence of HER2-low status, suggesting a high degree of variation in pathologic assessment of HER2 expression without impact on outcomes.

Quality of life in women with early-stage and metastatic hormone receptor-positive, HER2-negative breast cancer receiving endocrine therapy

INTRODUCTION

Early discontinuation of endocrine therapy (ET) is higher among patients with early breast cancer (EBC) compared to patients with metastatic hormone receptor-positive (HR+) breast cancer (MBC). In our clinical experience the reasons for this may include a significant burden of ET side effects impacting quality of life (QOL) in patients with EBC. We hypothesized that QOL is lower in patients with HR + EBC compared to patients with HR + MBC on ET.

METHODS

We conducted a cross-sectional observational study to assess QOL utilizing FACT-ES & EORTC QLQ C30 tools among patients with EBC and MBC receiving ET across 5 Irish hospitals.

RESULTS

A total of 417 patients were enrolled-EBC (79% n = 331) and MBC 21% (n = 86). Using the FACT-ES, we found no difference in overall QOL by stage (139.2 vs 141, P  = .33). Patients with HR + MBC had a lower symptom burden from ET compared to HR + EBC (61.4 vs 54, P < .01). In adjusted multivariate linear regression models, there was no difference in QOL for patients with EBC and MBC receiving ET.

CONCLUSIONS

There was no significant difference in overall QOL for patients with EBC and MBC. However, patients with EBC experienced more endocrine symptoms. In adjusted multivariate linear regression models, the stage did not predict QOL. Our results suggest that endocrine symptoms are significant contributors to impaired QOL for patients with EBC but the role of other determinants of QOL (eg, stage) is less clear. Future work could include the development of stage-specific QOL tools and utilization of electronic patient-reported outcomes (ePROs) to identify and manage emergent toxicities.

Elacestrant in ER+, HER2- Metastatic Breast Cancer with ESR1-Mutated Tumors: Subgroup Analyses from the Phase III EMERALD Trial by Prior Duration of Endocrine Therapy plus CDK4/6 Inhibitor and in Clinical Subgroups

PURPOSE

Elacestrant significantly prolonged progression-free survival (PFS) with manageable safety versus standard-of-care (SOC) endocrine therapy (ET) in patients with estrogen receptor-positive (ER+), HER2- metastatic breast cancer and tumors harboring estrogen receptor 1 (ESR1) mutation following ET plus a cyclin-dependent kinase 4/6 inhibitor (ET+CDK4/6i). In patients with ESR1-mutated tumors, we evaluated the efficacy and safety of elacestrant versus SOC based on prior ET+CDK4/6i duration and in clinical subgroups with prior ET+CDK4/6i ≥12 months.

PATIENTS AND METHODS

EMERALD, an open-label phase III trial, randomly assigned patients with ER+, HER2- metastatic breast cancer who had received 1-2 prior lines of ET, mandatory CDK4/6i, and ≤1 chemotherapy to elacestrant (345 mg daily) or SOC (aromatase inhibitor or fulvestrant). PFS was assessed across subgroups in post hoc exploratory analyses without adjustment for multiple testing.

RESULTS

In patients with ESR1-mutated tumors and prior ET+CDK4/6i ≥12 months, the median PFS for elacestrant versus SOC was 8.6 versus 1.9 months (HR, 0.41; 95% confidence interval, 0.26-0.63). In this population, the median PFS (in months) for elacestrant versus SOC was 9.1 versus 1.9 (bone metastases), 7.3 versus 1.9 (liver and/or lung metastases), 9.0 versus 1.9 (<3 metastatic sites), 10.8 versus 1.8 (≥3 metastatic sites), 5.5 versus 1.9 (PIK3 catalytic subunit α mutation), 8.6 versus 1.9 (tumor protein p53 gene mutation), 9.0 versus 1.9 (HER2-low), 9.0 versus 1.9 (ESR1D538G-mutated tumors), and 9.0 versus 1.9 (ESR1Y537S/N-mutated tumors). Subgroup safety was consistent with the overall population.

CONCLUSIONS

The duration of prior ET+CDK4/6i ≥12 months in metastatic breast cancer was associated with a clinically meaningful improvement in PFS for elacestrant compared with SOC and was consistent across all subgroups evaluated in patients with ER+, HER2-, ESR1-mutated tumors.

Dalpiciclib in combination with letrozole/anastrozole or fulvestrant in HR-positive and HER2-negative advanced breast cancer: results from a phase Ib study

Background

Dalpiciclib is a novel cyclin-dependent kinase 4/6 inhibitor which showed tolerability and preliminary efficacy as monotherapy for pretreated advanced breast cancer (BC).

Objectives

To further assess dalpiciclib with endocrine therapy (ET) in hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative BC.

Design

A multicenter, open-label, phase Ib trial.

Methods

Patients with locally recurrent or metastatic BC were enrolled in five cohorts. Patients without prior treatment for advanced disease (cohorts 1-2) were given dalpiciclib (125 or 150 mg) plus letrozole/anastrozole; patients who progressed after ET (cohorts 3-5) were given dalpiciclib (125, 150, or 175 mg) plus fulvestrant. Dalpiciclib was administered orally once daily in 3-weeks-on/1-week off schedule. The primary endpoint was safety.

Results

A total of 58 patients received dalpiciclib with letrozole/anastrozole and 46 received dalpiciclib with fulvestrant. No maximum tolerated dose of dalpiciclib was reached with letrozole/anastrozole or fulvestrant. Across all cohorts, 86.7%-93.8% of patients had a grade ⩾3 adverse event, with the most common being neutropenia (grade 3, 40.0% for dalpiciclib 175 mg and 61.8%-87.5% for lower doses; grade 4, 46.7% and 4.2%-20.6%, respectively) and leukopenia (grade 3, 80.0% for 175 mg and 33.3%-54.2% for lower doses; grade 4, 0% for all doses). At tested dose levels, steady-state areas under the concentration curve and peak concentration of dalpiciclib increased with dose when combined with letrozole/anastrozole and fulvestrant. Dalpiciclib at 150 mg was associated with a numerically higher objective response rate in both patients untreated for advanced disease (67.6%; 95% confidence interval (CI) 49.5-82.6) and patients progressing after ET (53.3%; 95% CI 26.6-78.7); as of July 30, 2022, the median progression-free survival with dalpiciclib 150 mg was 24.1 months (95% CI 16.9-46.0) with letrozole/anastrozole and 16.7 months (95% CI 1.9-24.1) with fulvestrant.

Conclusion

Dalpiciclib plus letrozole/anastrozole or fulvestrant showed an acceptable safety profile. The recommended phase III dose of dalpiciclib was 150 mg.

Trial registration

ClinicalTrials.gov identifier: NCT03481998.

Real-world treatment patterns and outcomes in patients with HR+/HER2- metastatic breast cancer treated with chemotherapy in the United States

BACKGROUND

Until recently, treatment options for patients with hormone receptor-positive/human epidermal growth factor 2-negative (HR+/HER2-) metastatic breast cancer (mBC) and resistance to endocrine therapy were limited to chemotherapy. This real-world study describes treatment patterns and outcomes in patients treated with chemotherapy in the United States before approval of antibody-drug conjugates.

PATIENTS AND METHODS

This retrospective, observational study included adults with HR+/HER2- mBC from the ConcertAI Patient360™ Breast Cancer dataset who initiated their first chemotherapy in the metastatic setting between January 2011 and June 2021. Treatment patterns were described; real-world overall survival, time to next treatment or death, and real-world progression-free survival were evaluated for all eligible patients and patients treated with subsequent chemotherapy. Index dates were the start date of each chemotherapy treatment.

RESULTS

Among 1545 eligible patients, 76% were white, 12% had Eastern Cooperative Oncology Group performance status ≥2, 38% had de novo mBC, and median age was 61 years (range, 52-69 years). Within the index period, capecitabine was used the most as the first chemotherapy agent and decreased in later treatments, while the use of eribulin increased between first and fourth chemotherapies. Median (95% confidence interval) real-world overall survival was 23.3 months (21.3-25.4 months) from start of first chemotherapy, time to next treatment or death was 6.5 months (5.9-7.1 months), and real-world progression-free survival was 6.9 months (6.4-7.6 months); median times from second, third, and fourth chemotherapies decreased with each additional chemotherapy treatment.

CONCLUSIONS

This real-world study demonstrates that for patients with HR+/HER2- mBC, chemotherapy provides relatively limited survival benefit which decreases with each additional chemotherapy line, and highlights the need for improved treatment options.

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.

Palbociclib: Randomized Studies and Real-world Evidence as the Basis for Therapeutic Planning in Metastatic Breast Cancer

Endocrine-based combination therapy with an inhibitor of the cyclin-dependent kinases 4 and 6 (CDK4/6 inhibitors) is currently the first-line therapy of choice for patients with hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-), locally advanced or metastatic breast cancer (mBC). The efficacy and safety of the treatment with palbociclib, the first CDK4/6 inhibitor approved for this indication, have been confirmed in large randomized controlled clinical trials (RCTs) with strictly defined patient cohorts. Since then, many relevant questions about CDK4/6 inhibition with palbociclib for mBC have been investigated in RCTs and real-world studies. Based on this evidence, palbociclib is widely used in clinical practice since many years because of its efficacy and good tolerability. The aim of this review is to summarize findings from RCTs and RWE considering clinically relevant aspects such as safety, tolerability, quality of life and efficacy with a focus on specific questions and patient characteristics. A critical discussion and review of the overall evidence for endocrine-based therapy with the CDK4/6 inhibitor palbociclib can contribute to support therapy decisions in daily clinical practice.

Cost-effectiveness of early vs delayed use of abemaciclib combination therapy for patients with high-risk hormone receptor-positive/human epidermal growth factor receptor 2-negative early breast cancer

BACKGROUND

Abemaciclib was newly approved for hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) high-risk early breast cancer (EBC). Clinical guidelines recommended abemaciclib as the first-line treatment for HR+/ HER2- EBC (early use) or HR+/ HER2- metastatic breast cancer (MBC) (delayed use).

OBJECTIVE

To compare the cost-effectiveness of early vs delayed use of abemaciclib for treatment of HR+/HER2- high-risk EBC. Early use was defined as combined abemaciclib and endocrine therapy as first-line therapy for EBC, followed by treatment with fulvestrant for MBC. Delayed use was defined as endocrine therapy for EBC, followed by combined abemaciclib and fulvestrant therapy for MBC.

METHODS

A 5-state model was developed to estimate lifetime costs, life-years (LYs), and quality-adjusted life-years (QALYs) of hypothetical patients with HR+/ HER2- EBC from a third-party US payer's perspective. Key clinical and safety data were derived from the monarchE and MONARCH 2 clinical trials. Costs, utilities, and disutility values of adverse events were obtained from the literature. We calculated the incremental cost-effectiveness ratio (ICER) of early vs delayed abemaciclib use and compared it with a willingness-to-pay (WTP) threshold of $100,000 per LY or QALY. Deterministic and probabilistic sensitivity analyses (PSAs) were performed to test the robustness of the base-case model.

RESULTS

Base-case analysis showed early use yielded 21.08 LYs and 17.93 QALYs for $586,213 and delayed use yielded 11.14 LYs and 9.38 QALYs for $157,576. The ICER of early vs delayed use was $43,136/LY and $50,104/QALY, which was cost-effective at the WTP threshold of $100,000. The PSA result indicated that a 94.6% likelihood of early use (vs delayed use) was cost-effective at the WTP threshold of $100,000 per QALY.

CONCLUSIONS

This study suggests that giving abemaciclib in the early stage rather than waiting until patients develop metastatic disease (current standard of care in MBC) is a cost-effective strategy.