Patterns of treatment with everolimus exemestane in hormone receptor-positive HER2-negative metastatic breast cancer in the era of targeted therapy

The Importance of Cancer Stem Cells and Their Pathways in Endometrial Cancer: A Narrative Review

Endometrial cancer is one of the most common malignancies seen in women in developed countries. While patients in the early stages of this cancer show better responses to surgery, adjuvant hormonal therapy, and chemotherapy, patients with recurrence show treatment resistance. Researchers have recently focused on cancer stem cells (CSCs) in the treatment of gynecologic cancer in general but also specifically in endometrial cancer. CSCs have been investigated because of their resistance to conventional therapies, such as chemo- and radiotherapy, and their ability to induce the progression and recurrence of malignancy. The activation of alternative pathways, such as WNT, PI3K, NF-kB, or NOTCH, could be the basis of the acquisition of these abilities of CSCs. Their specific markers and signaling pathways could be treatment targets for CSCs. In this article, we discuss the importance of obtaining a better understanding of the molecular basis and pathways of CSCs in endometrial cancer and the role of CSCs, aiming to discover more specific therapeutic approaches.

Artemisitene induces apoptosis of breast cancer cells by targeting FDFT1 and inhibits the growth of breast cancer patient-derived organoids

Artemisitene (ATT) is a natural bioactive compound with anti-breast cancer activity. However, the direct target and clinical efficacy of ATT on breast cancer are still unclear. The current study aimed to identify the target protein and underlying mechanism of ATT in anti-breast cancer. Moreover, patient-derived organoids (PDOs) were employed to assess the clinical efficacy of ATT on breast cancer. Herein, molecular docking, molecular dynamics simulation, cellular thermal shift assay (CETSA) combined with Western blot, surface plasmon resonance (SPR) were applied to confirm the interactional target of ATT in breast cancer cells. Bioinformatics analysis, Western blot, flow cytometry, plasmid construction and lentivirus infection, chromatin immunoprecipitation (ChIP) assay, and quantitative real-time PCR (RT-qPCR) were performed to reveal the potential mechanism of ATT in treating breast cancer. PDOs were established to evaluate the clinical therapeutic efficiency of ATT on breast cancer. We found that ATT interacted with Farnesyl-diphosphate farnesyltransferase 1 (FDFT1) in breast cancer cells. Knockdown of FDFT1 induced NEDD4 expression and apoptosis in breast cancer cells. Overexpression of FDFT1 could rescue ATT-induced apoptosis, while interfering with FDFT1 expression decreased the level of RelA (NF-κB p65 subunit) in the nucleus in breast cancer cells. Knockdown of FDFT1 induced NEDD4 expression by regulating TNFR1/NF-κB pathway. Overexpression of FDFT1 could reverse the activation of ATT-induced TNFR1/NF-κB/NEDD4 pathway in breast cancer cells. Interestingly, the ChIP assay and RT-qPCR revealed that p65 could regulate NEDD4 transcription. Furthermore, ATT exhibited a broad-spectrum inhibitory effect on the growth of breast cancer PDOs with different pathological subtypes, and showed an excellent safety profile in comparison with that of conventional chemotherapy drugs. In summary, this work demonstrated that ATT targets FDFT1 to induce apoptosis of breast cancer cells through regulating TNFR1/NF-κB/NEDD4 pathway and suppresses breast cancer PDOs growth, which supported ATT as an effective and potential drug candidate for breast cancer treatment.

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.

Targeted therapy of cancer stem cells: inhibition of mTOR in pre-clinical and clinical research

Cancer stem cells (CSCs) are a type of stem cell that possesses not only the intrinsic abilities of stem cells but also the properties of cancer cells. Therefore, CSCs are known to have self-renewal and outstanding proliferation capacity, along with the potential to differentiate into specific types of tumor cells. Cancers typically originate from CSCs, making them a significant target for tumor treatment. Among the related cascades of the CSCs, mammalian target of rapamycin (mTOR) pathway is regarded as one of the most important signaling pathways because of its association with significant upstream signaling: phosphatidylinositol 3‑kinase/protein kinase B (PI3K/AKT) pathway and mitogen‑activated protein kinase (MAPK) cascade, which influence various activities of stem cells, including CSCs. Recent studies have shown that the mTOR pathway not only affects generation of CSCs but also the maintenance of their pluripotency. Furthermore, the maintenance of pluripotency or differentiation into specific types of cancer cells depends on the regulation of the mTOR signal in CSCs. Consequently, the clinical potential and importance of mTOR in effective cancer therapy are increasing. In this review, we demonstrate the association between the mTOR pathway and cancer, including CSCs. Additionally, we discuss a new concept for anti-cancer drug development aimed at overcoming existing drawbacks, such as drug resistance, by targeting CSCs through mTOR inhibition.

Phase III Randomized, Placebo-Controlled Trial of Endocrine Therapy ± 1 Year of Everolimus in Patients With High-Risk, Hormone Receptor-Positive, Early-Stage Breast Cancer

PURPOSE

Phosphatidylinositol 3-kinase/AKT-serine threonine kinase/mammalian target of rapamycin (mTOR) pathway abnormalities contribute to endocrine resistance. Everolimus, an mTOR inhibitor, improved progression-free survival in hormone receptor-positive metastatic breast cancer (BC) when combined with endocrine therapy (ET). In this phase III randomized, placebo-controlled trial, we assessed the efficacy of everolimus + ET as adjuvant therapy in high-risk, hormone receptor-positive, human epidermal growth factor receptor 2-negative BC after adjuvant/neoadjuvant chemotherapy.

METHODS

Patients were randomly assigned 1:1 to physician's choice ET and 1 year of everolimus (10 mg orally once daily) or placebo stratified by risk group. The primary end point was invasive disease-free survival (IDFS) evaluated by a stratified log-rank test with the hazard ratio (HR) estimated by Cox regression. Subset analyses included preplanned evaluation by risk group and exploratory analyses by menopausal status and age. Secondary end points included overall survival (OS) and safety. Everolimus did not improve IDFS/OS when added to ET in patients with early-stage high-risk, hormone receptor-positive BC.

RESULTS

One thousand and nine hundred thirty-nine patients were randomly assigned with 1,792 eligible for analysis. Overall, no benefit of everolimus was seen for IDFS (HR, 0.94 [95% CI, 0.77 to 1.14]) or OS (HR, 0.97 [95% CI, 0.75 to 1.26]). The assumption of proportional hazards was not met suggesting significant variability in the HR over time since the start of treatment. In an unplanned subgroup analysis among postmenopausal patients (N = 1,221), no difference in IDFS (HR, 1.08 [95% CI, 0.86 to 1.36]) or OS (HR, 1.19 [95% CI, 0.89 to 1.60]) was seen. In premenopausal patients (N = 571), everolimus improved both IDFS (HR, 0.64 [95% CI, 0.44 to 0.94]) and OS (HR, 0.49 [95% CI, 0.28 to 0.86]). Treatment completion rates were lower in the everolimus arm compared with placebo (48% v 73%) with higher grade 3 and 4 adverse events (35% v 7%).

CONCLUSION

One year of adjuvant everolimus + ET did not improve overall outcomes. Subset analysis suggests mTOR inhibition as a possible target for patients who remain premenopausal after chemotherapy.

Everolimus plus endocrine therapy beyond CDK4/6 inhibitors progression for HR+ /HER2- advanced breast cancer: a real-world evidence cohort

PURPOSE

Everolimus in combination with endocrine therapy (ET) was formerly approved as 2nd-line therapy in HR(+)/HER2(-) advanced breast cancer (aBC) patients (pts) progressing during or after a non-steroidal aromatase inhibitor (NSAI). Since this approval, the treatment landscape of aBC has changed dramatically, particularly with the arrival of CDK 4-6 inhibitors. Endocrine monotherapy after progression to CDK4/6 inhibitors has shown a limited progression-free survival (PFS), below 3 months. Evidence of the efficacy of everolimus plus ET after CDK4/6 inhibitors is scarce.

METHODS

A retrospective observational study of patients with aBC treated with everolimus and ET beyond CDK4/6-i progression compiled from February 2015 to December 2022 in 4 Spanish hospitals was performed. Clinical and demographic data were collected from medical records. The main objective was to estimate the median progression-free survival (mPFS). Everolimus adverse events (AE) were registered. Quantitative variables were summarized with medians; qualitative variables with proportions and the Kaplan-Meier method were used for survival estimates.

RESULTS

One hundred sixty-one patients received everolimus plus ET (exemestane: 96, fulvestrant: 54, tamoxifen: 10, unknown: 1) after progressing on a CDK4/6 inhibitor. The median follow-up time was 15 months (interquartile range: 1-56 months). The median age at diagnosis was 49 years (range: 35-90 years). The estimated mPFS was 6.0 months (95%CI 5.3-7.8 months). PFS was longer in patients with previous CDK4/6 inhibitor therapy lasting for > 18 months (8.7 months, 95%CI 6.6-11.3 months), in patients w/o visceral metastases (8.0 months, 95%CI 5.8-10.5 months), and chemotherapy-naïve in the metastatic setting (7.2 months, 95%CI 5.9-8.4 months).

CONCLUSION

This retrospective analysis cohort of everolimus plus ET in mBC patients previously treated with a CDK4/6 inhibitor suggests a longer estimated mPFS when compared with the mPFS with ET monotherapy obtained from current randomized clinical data. Everolimus plus ET may be considered as a valid control arm in novel clinical trial designs.

Breast Cancer Stem Cells and Tumor Heterogeneity: Characteristics and Therapeutic Strategies

Breast cancer is one of the most frequently detected malignancies worldwide. It is responsible for more than 15% of all death cases caused by cancer in women. Breast cancer is a heterogeneous disease representing various histological types, molecular characteristics, and clinical profiles. However, all breast cancers are organized in a hierarchy of heterogeneous cell populations, with a small proportion of cancer stem cells (breast cancer stem cells (BCSCs)) playing a putative role in cancer progression, and they are responsible for therapeutic failure. In different molecular subtypes of breast cancer, they present different characteristics, with specific marker profiles, prognoses, and treatments. Recent efforts have focused on tackling the Wnt, Notch, Hedgehog, PI3K/Akt/mTOR, and HER2 signaling pathways. Developing diagnostics and therapeutic strategies enables more efficient elimination of the tumor mass together with the stem cell population. Thus, the knowledge about appropriate therapeutic methods targeting both "normal" breast cancer cells and breast cancer stem cell subpopulations is crucial for success in cancer elimination.

BOLERO-5: a phase II study of everolimus and exemestane combination in Chinese post-menopausal women with ER + /HER2- advanced breast cancer

BACKGROUND

The global BOLERO-2 trial established the efficacy and safety of combination everolimus (EVE) and exemestane (EXE) in the treatment of estrogen receptor positive (ER +), HER2-, advanced breast cancer (ABC). BOLERO-5 investigated this combination in a Chinese population (NCT03312738).

METHODS

BOLERO-5 is a randomized, double-blind, multicenter, placebo controlled, phase II trial comparing EVE (10 mg/day) or placebo (PBO) in combination with EXE (25 mg/day). The primary endpoint was progression-free survival (PFS) per investigator assessment. Secondary endpoints included PFS per blinded independent review committee (BIRC), overall survival (OS), overall response rate (ORR), clinical benefit rate (CBR), pharmacokinetics, and safety.

RESULTS

A total of 159 patients were randomized to EVE + EXE (n = 80) or PBO + EXE (n = 79). By investigator assessment, treatment with EVE + EXE prolonged median PFS by 5.4 months (HR 0.52; 90% CI 0.38, 0.71), from 2.0 months (PBO + EXE; 90% CI 1.9, 3.6) to 7.4 months (EVE + EXE; 90% CI 5.5, 9.0). Similar results were observed following assessment by BIRC, with median PFS prolonged by 4.3 months. Treatment with EVE + EXE was also associated with improvements in ORR and CBR. No new safety signals were identified in BOLERO-5, with the incidence of adverse events in Chinese patients consistent with the safety profile of both drugs.

CONCLUSION

The efficacy and safety results of BOLERO-5 validate the findings from BOLERO-2, and further support the use of EVE + EXE in Chinese post-menopausal women with ER + , HER2- ABC. NCT03312738, registered 18 October 2017.

Systematic literature review of real-world evidence for treatments in HR+/HER2- second-line LABC/mBC after first-line treatment with CDK4/6i

BACKGROUND

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) are currently recommended by the National Comprehensive Cancer Network (NCCN) guidelines and the European Society for Medical Oncology (ESMO) guidelines as the first-line (1 L) treatment for patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative, locally advanced/metastatic breast cancer (HR+/HER2- LABC/mBC). Although there are many treatment options, there is no clear standard of care for patients following 1 L CDK4/6i. Understanding the real-world effectiveness of subsequent therapies may help to identify an unmet need in this patient population. This systematic literature review qualitatively synthesized effectiveness and safety outcomes for treatments received in the real-world setting after 1 L CDK4/6i therapy in patients with HR+/ HER2- LABC/mBC.

METHODS

MEDLINE®, Embase, and Cochrane were searched using the Ovid® platform for real-world evidence studies published between 2015 and 2022. Grey literature was searched to identify relevant conference abstracts published from 2019 to 2022. The review was conducted in accordance with PRISMA guidelines (PROSPERO registration: CRD42023383914). Data were qualitatively synthesized and weighted average median real-world progression-free survival (rwPFS) was calculated for NCCN/ESMO-recommended post-1 L CDK4/6i treatment regimens.

RESULTS

Twenty records (9 full-text articles and 11 conference abstracts) encompassing 18 unique studies met the eligibility criteria and reported outcomes for second-line (2 L) treatments after 1 L CDK4/6i; no studies reported disaggregated outcomes in the third-line setting or beyond. Sixteen studies included NCCN/ESMO guideline-recommended treatments with the majority evaluating endocrine-based therapy; five studies on single-agent ET, six studies on mammalian target of rapamycin inhibitors (mTORi) ± ET, and three studies with a mix of ET and/or mTORi. Chemotherapy outcomes were reported in 11 studies. The most assessed outcome was median rwPFS; the weighted average median rwPFS was calculated as 3.9 months (3.3-6.0 months) for single-agent ET, 3.6 months (2.5-4.9 months) for mTORi ± ET, 3.7 months for a mix of ET and/or mTORi (3.0-4.0 months), and 6.1 months (3.7-9.7 months) for chemotherapy. Very few studies reported other effectiveness outcomes and only two studies reported safety outcomes. Most studies had heterogeneity in patient- and disease-related characteristics.

CONCLUSIONS

The real-world effectiveness of current 2 L treatments post-1 L CDK4/6i are suboptimal, highlighting an unmet need for this patient population.

MYC is a clinically significant driver of mTOR inhibitor resistance in breast cancer

Targeting the PI3K-AKT-mTOR pathway is a promising therapeutic strategy for breast cancer treatment. However, low response rates and development of resistance to PI3K-AKT-mTOR inhibitors remain major clinical challenges. Here, we show that MYC activation drives resistance to mTOR inhibitors (mTORi) in breast cancer. Multiomic profiling of mouse invasive lobular carcinoma (ILC) tumors revealed recurrent Myc amplifications in tumors that acquired resistance to the mTORi AZD8055. MYC activation was associated with biological processes linked to mTORi response and counteracted mTORi-induced translation inhibition by promoting translation of ribosomal proteins. In vitro and in vivo induction of MYC conferred mTORi resistance in mouse and human breast cancer models. Conversely, AZD8055-resistant ILC cells depended on MYC, as demonstrated by the synergistic effects of mTORi and MYCi combination treatment. Notably, MYC status was significantly associated with poor response to everolimus therapy in metastatic breast cancer patients. Thus, MYC is a clinically relevant driver of mTORi resistance that may stratify breast cancer patients for mTOR-targeted therapies.

XENERA-1: a randomised double-blind Phase II trial of xentuzumab in combination with everolimus and exemestane versus everolimus and exemestane in patients with hormone receptor-positive/HER2-negative metastatic breast cancer and non-visceral disease

BACKGROUND

Xentuzumab is a humanised monoclonal antibody that binds to IGF-1 and IGF-2, neutralising their proliferative activity and restoring inhibition of AKT by everolimus. This study evaluated the addition of xentuzumab to everolimus and exemestane in patients with advanced breast cancer with non-visceral disease.

METHODS

This double-blind, randomised, Phase II study was undertaken in female patients with hormone-receptor (HR)-positive/human epidermal growth factor 2 (HER2)-negative advanced breast cancer with non-visceral disease who had received prior endocrine therapy with or without CDK4/6 inhibitors. Patients received a weekly intravenous infusion of xentuzumab (1000 mg) or placebo in combination with everolimus (10 mg/day orally) and exemestane (25 mg/day orally). The primary endpoint was progression-free survival (PFS) per independent review.

RESULTS

A total of 103 patients were randomised and 101 were treated (n = 50 in the xentuzumab arm and n = 51 in the placebo arm). The trial was unblinded early due to high rates of discordance between independent and investigator assessment of PFS. Per independent assessment, median PFS was 12.7 (95% CI 6.8-29.3) months with xentuzumab and 11.0 (7.7-19.5) months with placebo (hazard ratio 1.19; 95% CI 0.55-2.59; p = 0.6534). Per investigator assessment, median PFS was 7.4 (6.8-9.7) months with xentuzumab and 9.2 (5.6-14.4) months with placebo (hazard ratio 1.23; 95% CI 0.69-2.20; p = 0.4800). Tolerability was similar between the arms, with diarrhoea (33.3-56.0%), fatigue (33.3-44.0%) and headache (21.6-40.0%) being the most common treatment-emergent adverse events. The incidence of grade ≥ 3 hyperglycaemia was similar between the xentuzumab (2.0%) and placebo (5.9%) arms.

CONCLUSIONS

While this study demonstrated that xentuzumab could be safely combined with everolimus and exemestane in patients with HR-positive/HER2-negative advanced breast cancer with non-visceral disease, there was no PFS benefit with the addition of xentuzumab. Trial registration ClinicalTrials.gov, NCT03659136. Prospectively registered, September 6, 2018.

Analysis of real-world data to investigate evolving treatment sequencing patterns in advanced non-small cell lung cancers and their impact on survival

Background

Although optimal sequencing of systemic therapy in cancer care is critical to achieving maximal clinical benefit, there is a lack of analysis of treatment sequencing in advanced non-small cell lung cancer (aNSCLC) in real-world settings.

Methods

A retrospective cohort study of 13,340 lung cancer patients within the Mount Sinai Health System (MSHS) was performed. Systemic therapy data of aNSCLC in 2,106 patients was the starting point in our analysis to investigate how treatment sequencing has evolved, the impact of sequencing patterns on clinical outcomes, and the effectiveness of 2nd line chemotherapy after patients progressed on immune checkpoint inhibitor (ICI)-based therapy as the 1st line of therapy (LOT).

Results

There is a significant shift to more ICI-based therapy and multiple lines of targeted therapy after 2015. We compared clinical outcomes of two patient populations with different treatment sequencing patterns, with the 1st group receiving chemotherapy as the 1st LOT followed by ICI-based treatment, and the 2nd group treated in the opposite order receiving a 1st line ICI-containing regimen followed by a 2nd line chemotherapy. No statistically significant difference in overall survival (OS) was observed between the two groups [group 2 vs. group 1, adjusted hazard ratio (aHR) =1.36, P=0.39]. We assessed the efficacy of the 2nd line chemotherapy in three patient populations given either 1st line ICI single agent, 1st line ICI-chemotherapy combination, or 1st line chemotherapy alone, there was no statistically significant difference in time-to-next treatment (TTNT) and in OS among the three patient groups.

Conclusions

Analysis of real-world data has shown two treatment sequencing patterns in aNSCLC, ICI followed by chemotherapy or chemotherapy followed by ICI, achieved similar clinical benefit. The chemotherapies routinely used following platinum doublet 1st LOT, is effective as the 2nd line option after ICI-chemotherapy combination in the 1st line setting.

Evaluating everolimus for the treatment of breast cancer

INTRODUCTION

Everolimus is an oral drug that inhibits mTOR with immunosuppressive and antiproliferative characteristics. It is commonly used in association with exemestane in hormone receptor (HR)-positive advanced breast cancer (ABC).

AREAS COVERED

The current review summarizes the publications relating to everolimus from clinical research in breast cancer. Everolimus showed treatment efficacy and an acceptable safety tolerance with prevention of side effects in Phase II/III studies. BOLERO-2 study showed a progression-free survival improvement in patients with HR-positive ABC previously treated with aromatase inhibitors (AI) and leading to its acceptance in this indication. The absence of a post CDK4/6 inhibitor (CDK4/6i.) study and the arrival of new drugs may raise questions about its current place in the therapeutic strategy.

EXPERT OPINION

Everolimus is relevant in the management of HR-positive ABC. Because of its efficacy, acceptable tolerability and the absence of drugs that have shown a greater benefit, it remains a second-line treatment option in HR-positive, HER2 negative (score 0) patients without BRCA mutation or visceral crisis and can be discuss with fulvestrant in second line after CDK4-6i. It is likely that within 5 years this treatment will be replaced in second line HR-positive breast cancer by new emerging treatments: drug-conjugated antibodies, tyrosine kinase inhibitors or immunotherapy in combination with chemotherapy.

Place in Therapy of Cyclin-Dependent Kinase 4/6 Inhibitors in Breast Cancer: A Targeted Literature Review

Cyclin-dependent kinase 4 and 6 inhibitors (CDK4/6i) are the preferred regimen for patients with hormone receptor-positive and human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced or metastatic breast cancer. However, the optimal treatment sequencing for CDK4/6i with other available therapeutic options is unclear. We conducted a targeted literature review to identify the current evidence on CDK4/6i treatment patterns in patients with breast cancer. The search was initially conducted in October 2021 and subsequently updated in October 2022. Biomedical databases and gray literature were searched, and bibliographies of included reviews were screened for relevant studies. The search identified ten reviews published since 2021 and 87 clinical trials or observational studies published since 2015. The included reviews discussed CDK4/6i usage with or without endocrine therapy (ET) in first-line and second-line treatment for patients with HR+/HER2- advanced or metastatic breast cancer, followed by ET, chemotherapy, or targeted therapy with ET. Clinical studies reported similar treatment sequences consisting of ET, chemotherapy, or targeted therapy with ET prior to CDK4/6i with ET, followed by ET monotherapy, chemotherapy, targeted therapy with ET, or continued CDK4/6i with ET. Current evidence suggests CDK4/6i are effective for HR+/HER2- advanced or metastatic breast cancer in earlier lines of therapy. Efficacy of CDK4/6i as measured by progression-free survival and overall survival was similar within a line of therapy regardless of the type of prior therapy. Survival on different post-CDK4/6i treatments was also similar within the same line of therapy. Additional research is needed to investigate the optimal place in therapy of CDK4/6i and the sequencing of treatments following progression on CDK4/6i.

Long-Term Results with Everolimus in Advanced Hormone Receptor Positive Breast Cancer in a Multicenter National Real-World Observational Study

Everolimus is the first oral targeted therapy widely used in advanced HR+/HER2- breast cancer. We sought to evaluate the impact of everolimus-based therapy on overall survival in the ESME-MBC database, a national metastatic breast cancer cohort that collects retrospective data using clinical trial-like methodology including quality assessments. We compared 1693 patients having received everolimus to 5928 patients not exposed to everolimus in the same period. Overall survival was evaluated according to treatment line, and a propensity score with the inverse probability of treatment weighting method was built to adjust for differences between groups. Crude and landmark overall survival analyses were all compatible with a benefit from everolimus-based therapy. Adjusted hazard ratios for overall survival were 0.34 (95% CI: 0.16-0.72, p = 0.0054), 0.34 (95% CI: 0.22-0.52, p < 0.0001), and 0.23 (95% CI: 0.14-0.36, p < 0.0001) for patients treated with everolimus in line 1, 2, and 3 and beyond, respectively. No clinically relevant benefit on progression-free survival was observed. Causes for everolimus discontinuation were progressive disease (56.2%), adverse events (27.7%), and other miscellaneous reasons. Despite the limitations inherent to such retrospective studies, these results suggest that adding everolimus-based therapy to the therapeutic sequences in patients with advanced HR+/HER2- breast cancer may favorably affect overall survival.

Efficacy of subsequent treatments in patients with hormone-positive advanced breast cancer who had disease progression under CDK 4/6 inhibitor therapy

BACKGROUND

There is no standard treatment recommended at category 1 level in international guidelines for subsequent therapy after cyclin-dependent kinase 4/6 inhibitor (CDK4/6) based therapy. We aimed to evaluate which subsequent treatment oncologists prefer in patients with disease progression under CDKi. In addition, we aimed to show the effectiveness of systemic treatments after CDKi and whether there is a survival difference between hormonal treatments (monotherapy vs. mTOR-based).

METHODS

A total of 609 patients from 53 centers were included in the study. Progression-free-survivals (PFS) of subsequent treatments (chemotherapy (CT, n:434) or endocrine therapy (ET, n:175)) after CDKi were calculated. Patients were evaluated in three groups as those who received CDKi in first-line (group A, n:202), second-line (group B, n: 153) and ≥ 3rd-line (group C, n: 254). PFS was compared according to the use of ET and CT. In addition, ET was compared as monotherapy versus everolimus-based combination therapy.

RESULTS

The median duration of CDKi in the ET arms of Group A, B, and C was 17.0, 11.0, and 8.5 months in respectively; it was 9.0, 7.0, and 5.0 months in the CT arm. Median PFS after CDKi was 9.5 (5.0-14.0) months in the ET arm of group A, and 5.3 (3.9-6.8) months in the CT arm (p = 0.073). It was 6.7 (5.8-7.7) months in the ET arm of group B, and 5.7 (4.6-6.7) months in the CT arm (p = 0.311). It was 5.3 (2.5-8.0) months in the ET arm of group C and 4.0 (3.5-4.6) months in the CT arm (p = 0.434). Patients who received ET after CDKi were compared as those who received everolimus-based combination therapy versus those who received monotherapy ET: the median PFS in group A, B, and C was 11.0 vs. 5.9 (p = 0.047), 6.7 vs. 5.0 (p = 0.164), 6.7 vs. 3.9 (p = 0.763) months.

CONCLUSION

Physicians preferred CT rather than ET in patients with early progression under CDKi. It has been shown that subsequent ET after CDKi can be as effective as CT. It was also observed that better PFS could be achieved with the subsequent everolimus-based treatments after first-line CDKi compared to monotherapy ET.

Clinical outcomes of tucidinostat-based therapy after prior CDK4/6 inhibitor progression in hormone receptor-positive heavily pretreated metastatic breast cancer

BACKGROUND

CDK4/6 inhibitors combined with endocrine therapy are standard first- or second-line treatment for patients with HR-positive and HER2-negative advanced breast cancer, however, there is currently no optimal recommendation for therapeutic strategies after progression on CDK4/6i. The aim of this study is to analyze the efficacy and safety of HDAC inhibitor Tucidinostat combined with endocrine therapy in patients after prior CDK4/6 inhibitor progression.

METHODS

The pathological and clinical data of 44 HR-positive and HER2-negative breast cancer patients treated with tucidinostat after progression on CDK4/6i at the Breast Oncology Department of the Fifth Medical Center of the PLA General Hospital from July 2019 to October 2021 were retrospectively analyzed. Observation indexes included progression-free survival (PFS), overall survival (OS), clinical benefit rate (CBR), objective response rate (ORR) and adverse events. At the same time, we attempted to identify potential genomic predictors using available next-generation sequencing (NGS).

RESULTS

A total of 44 patients were enrolled in this study. Median follow-up was 10 months (1-26 months) by the data cutoff date (February 2022). The CBR was 6.8% (3/44), the median PFS was 2.0 months (95% CI 1.9-2.1), and the median OS was 14 months (95% CI 6.3-21.7). The mPFS was 4.1 months (95%CI: 0-8.2) in patients with 1 metastatic site, and the mPFS was 4.5 months (95%CI: 4.2-4.8) in patients who received sequential tucidinostat after CDK4/6i failure. Multivariate analysis showed that patients with 1 metastatic site or sequential tucidinostat treatment after failure of CDK4/6i were more likely to benefit from tucidinostat combined with endocrine therapy. Preliminary data showed PIK3CA mutation may be associated with resistance of tucidinostat therapy. No grade 4 adverse events and no treatment-related deaths were recorded in the study. Dose reductions because of adverse events occurred in 4 (9.1%) patients.

CONCLUSIONS

This study preliminarily shows that tucidinostat combined with endocrine therapy may be an optional sequential strategy for patients with HR+/HER2-advanced breast cancer that has progressed on CDK4/6 inhibitor, especially for these with lower tumor burden and fewer prior palliative treatment.

Clinical management of metastatic hormone receptor-positive, HER2-negative breast cancer (MBC) after CDK 4/6 inhibitors: a retrospective single-institution study

PURPOSE

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is), in combination with endocrine therapy (ET), are standard either in the first (1L) or second-line (2L) setting for the treatment of hormone receptor (HR) positive, HER2-negative metastatic breast cancer (MBC). However, the optimal sequencing of treatments after progression on CDK4/6i remains unknown. We performed a single-institution analysis to identify treatments and outcomes after progression on a CDK4/6i.

METHODS

We identified patients with HR-positive, HER2-negative MBC prescribed a CDK4/6i in the 1L or 2L settings from December 2014 to February 2018 at Mayo Clinic in Rochester, Minnesota. Outcomes were collected through September 30, 2020.

RESULTS

Palbociclib, in combination with letrozole or fulvestrant, was the most prescribed CDK4/6i. The 1L and 2L CDK4/6i cohorts exhibited comparable overall survival (OS), but progression-free survival (PFS) was longer in the 1L than the 2L cohort [28.2 months (95% CI 19.6-34.9) vs 19.8 months (95% CI 15.7-29.6)]. The most common post-CDK4/6i treatments were PI3K/mTOR inhibitors (PI3K/mTORi), single-agent ET, or chemotherapy. PFS in the 1L CDK4/6i cohort following PI3K/mTORi was 8.5 months (95% CI 5.5 months-NE), single-agent ET was 6.0 months (95% CI 3.3-14.0 months), and chemotherapy PFS was 5.4 months (95% CI 3.3 months-NE).

CONCLUSIONS

Following progression on a CDK 4/6i, mPFS was short, with similar PFS times comparing chemotherapy and ET, with slightly longer PFS for targeted strategies (PI3K/mTOR). These results highlight a major need to better understand the mechanisms of CDK4/6i resistance and identify new therapeutic strategies for these patients.

Biomarkers of everolimus efficacy in breast cancer therapy

OBJECTIVE

Everolimus is an inhibitor of serine/ threonine kinase mTOR. The drug is approved for the treatment of metastatic ER positive, HER2 negative breast cancers and benefits a subset of patients with these breast cancers in combination with hormonal therapies. Despite extensive efforts, no additional predictive biomarkers to guide therapeutic decisions for everolimus have been introduced in clinical practice.

DATA SOURCES

This paper discusses predictive biomarkers for everolimus efficacy in breast cancer. A search of the medline and web of science databases was performed using the words "everolimus" and "biomarkers". References of retrieved articles were manually scanned for additional relevant articles.

DATA SUMMARY

Everolimus benefits a subset of patients with metastatic ER positive, HER2 negative breast cancers in combination with hormonal therapies. Despite extensive efforts no additional predictive biomarkers to guide therapeutic decisions for everolimus therapy have been confirmed for use in clinical practice. However, promising biomarker leads for everolimus efficacy in breast cancer have been suggested and include expression of proteins in the mTOR pathway in ER positive, HER2 negative breast cancers. In HER2 positive cancers PIK3CA mutations, and PTEN expression loss are prognostic. Other clinical predictive biomarkers with more limited data include characteristics derived from whole genome sequencing, subsets of circulating leukocytes and changes in Standardized Uptake Values (SUV) of Positron Emission Tomography (PET) scans.

CONCLUSIONS

Putative predictive biomarkers for everolimus efficacy in breast cancer patients, both genomic and clinical, deserve further study and could lead to a better selection of responsive patients.

Targeted Therapy in HR+ HER2- Metastatic Breast Cancer: Current Clinical Trials and Their Implications for CDK4/6 Inhibitor Therapy and beyond Treatment Options

A metastatic state of breast cancer (MBC) affects hundreds of thousands of women worldwide. In hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) MBC, cyclin-dependent kinase (CDK)4/6 inhibitors can improve the progression-free survival (PFS), as well as the overall survival (OS), in selected patients and have been established as first- and second-line therapies. However, as MBC remains uncurable, resistance to CDK4/6 inhibitors occurs and requires alternative treatment approaches. Data on targeted therapy continue to mature, and the number of publications has been constantly rising. This review provides a summary and update on the clinical relevance, patient selection, ongoing trials of CDK4/6 inhibitors, and further targeted therapy options. It focuses on clinical aspects and practicability, as well as adverse events and patient-reported outcomes.

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

PURPOSE

To update recommendations of the ASCO systemic therapy for hormone receptor (HR)-positive metastatic breast cancer (MBC) guideline.

METHODS

An Expert Panel conducted a systematic review to identify new, potentially practice-changing data.

RESULTS

Fifty-one articles met eligibility criteria and form the evidentiary basis for the recommendations.

RECOMMENDATIONS

Alpelisib in combination with endocrine therapy (ET) should be offered to postmenopausal patients, and to male patients, with HR-positive, human epidermal growth factor receptor 2 (HER2)-negative, PIK3CA-mutated, ABC, or MBC following prior endocrine therapy with or without a cyclin-dependent kinase (CDK) 4/6 inhibitor. Clinicians should use next-generation sequencing in tumor tissue or cell-free DNA in plasma to detect PIK3CA mutations. If no mutation is found in cell-free DNA, testing in tumor tissue, if available, should be used as this will detect a small number of additional patients with PIK3CA mutations. There are insufficient data at present to recommend routine testing for ESR1 mutations to guide therapy for HR-positive, HER2-negative MBC. For BRCA1 or BRCA2 mutation carriers with metastatic HER2-negative breast cancer, olaparib or talazoparib should be offered in the 1st-line through 3rd-line setting. A nonsteroidal aromatase inhibitor (AI) and a CDK4/6 inhibitor should be offered to postmenopausal women with treatment-naïve HR-positive MBC. Fulvestrant and a CDK4/6 inhibitor should be offered to patients with progressive disease during treatment with AIs (or who develop a recurrence within 1 year of adjuvant AI therapy) with or without one line of prior chemotherapy for metastatic disease, or as first-line therapy. Treatment should be limited to those without prior exposure to CDK4/6 inhibitors in the metastatic setting.Additional information can be found at www.asco.org/breast-cancer-guidelines.