Comparative efficacy of first- versus second-line CDK4/6 inhibition in hormone receptor-positive, HER2-negative metastatic breast cancer.

Purpose: The greater progression-free survival (PFS) improvements observed in first-line (1L) versus second-line (2L) CDK4/6 inhibitor (CDK4/6i) trials underpin current guideline recommendations establishing these agents as standard 1L therapy in hormone receptor-positive, HER2-negative (HR+/HER2-) metastatic breast cancer (mBC). While earlier CDK4/6i use is associated with increased cumulative toxicity and costs, comparative survival data of earlier versus deferred use remain scarce.

Methods: We performed a systematic review and meta-analysis, searching PubMed, Embase, Cochrane, and conference proceedings for observational studies and randomized clinical trials (RCTs) including patients treated with first- and/or 2L CDK4/6i.

Gedatolisib Combined with Palbociclib and Letrozole in Patients with No Prior Systemic Therapy for Hormone Receptor Positive, HER2 Negative Advanced Breast Cancer.

Purpose: Nonclinical evidence demonstrating that estrogen receptor (ER), CDK4/6, and PI3K/AKT/mTOR (PAM) pathways cross-promote tumor proliferation in HR+/HER2- breast cancer cell lines led to development of CDK4/6 inhibitors and agents inhibiting single PAM pathway nodes to treat HR+/HER2- advanced breast cancer (ABC). Simultaneous blockade of ER, CDK4/6 and PAM pathways may optimize anti-tumor control in the treatment-naïve ABC setting. Gedatolisib, a pan-PI3K/mTOR inhibitor, was evaluated as first-line therapy, combined with standard-of-care palbociclib and letrozole, for patients with HR+/HER2- ABC.

A 40-year-old woman with early-stage triple-negative breast cancer and a retinal lesion.

The development of highly sensitive diagnostic imaging tools has created a challenge in localized cancer therapy; incidental findings can complicate staging and decision making. In the absence of clinical symptoms suggestive of metastatic disease, the diagnostic approach to localized breast cancer typically does not mandate staging scans. While metastatic disease is often referred to as an incurable entity, oligometastatic disease, confined to a limited number of sites, may be amenable to curative-intent ablative therapy.

A bedside-to-bench translational analysis of NF1 alterations and CDK4/6 inhibitor resistance in hormone receptor-positive metastatic breast cancer.

Background: CDK4/6 inhibitors (CDK4/6i) are used for management of hormone receptor-positive (HR+) metastatic breast cancer (MBC), and activation of the RAS/MAPK and PI3K/AKT signalling pathways has been implicated in resistance to these agents. Pathogenic NF1 mutations (pNF1m) dysregulate RAS signalling, but NF1 has not been linked to CDK4/6i resistance. We analysed multi-institutional data, real-world evidence, and preclinical models to characterise the impact of pNF1m on CDK4/6i sensitivity.

Diffuse peritoneal inclusion cysts masquerading as disseminated gynecologic malignancy in post-menopausal females: Two cases and a review of the literature.

Peritoneal inclusion cysts are an important and underrecognized cause of benign pelvic and abdominal masses in post-menopausal patients. Diffuse peritoneal cysts in this population can be difficult to distinguish from disseminated gynecologic malignancy on imaging and laboratory evaluation and will often be managed by gynecologists and gynecologic oncologists. Preoperative diagnosis may be suspected in the setting of findings of thin-walled cystic lesions on imaging with indicative surgical or clinical history; however, given the risk of malignancy in this population, tissue diagnosis is necessary to exclude more serious diagnoses.

After a CDK4/6 Inhibitor: State of the Art in Hormone Receptor-Positive Metastatic Breast Cancer.

CDK 4/6 inhibitors (CDK4/6i) remain part of the standard first-line treatment for patients with hormone receptor-positive metastatic breast cancer, offering demonstrable improvements in both progression-free survival and overall survival. However, resistance inevitably develops, and the optimal treatment sequencing after CDK4/6i progression remains undefined. Tumor heterogeneity and diverse resistance mechanisms-including alterations in and -complicate treatment decisions in the post-CDK4/6i setting.

ELAINE 3: phase 3 study of lasofoxifene plus abemaciclib to treat ER+/HER2-, -mutated, metastatic breast cancer.

Endocrine therapy (ET) is recommended for patients with estrogen receptor-positive (ER+) metastatic breast cancer (mBC), but most patients will develop treatment resistance, often due to mutations in the ER-α-coding gene, . Therapeutic options are limited for endocrine-resistant mBC, particularly following treatment with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i). Lasofoxifene had anti-tumor activity in two separate phase 2, open-label studies (ELAINE 1 and 2) when given as monotherapy or combined with abemaciclib.

Cell cycle dysregulation in cancer.

Cancer is a systemic manifestation of aberrant cell cycle activity and dysregulated cell growth. Genetic mutations can determine tumor onset by either augmenting cell division rates or restraining normal controls such as cell cycle arrest or apoptosis. As a result, tumor cells not only undergo uncontrolled cell division but also become compromised in their ability to exit the cell cycle accurately.

Dynamic HER2-low status among patients with triple negative breast cancer (TNBC) and the impact of repeat biopsies.

Trastuzumab deruxtecan (T-DXd) is approved for HER2-low (HER2 immunohistochemistry (IHC)1+ or 2+ with non-amplified in situ hybridization (ISH)), but not HER2-0 (IHC 0) metastatic breast cancer. The impact of repeat biopsies (Bxs) in identifying new potential candidates with triple negative breast cancer (TNBC) for T-DXd treatment remains unknown. 512 consecutive patients with TNBC at diagnosis were included in the study cohort.

Adjuvant endocrine therapy with cyclin-dependent kinase 4/6 inhibitor, ribociclib, for localized hormone receptor-positive/HER2- breast cancer (LEADER).

Optimal timing and dosing of adjuvant cyclin-dependent kinase (CDK) 4/6 inhibitor in early breast cancer is controversial. This prospective phase II clinical trial investigated tolerability and safety of two ribociclib dosing schedules. Patients with stage I-III hormone receptor-positive (HR+)/HER2- breast cancer on adjuvant endocrine therapy (ET) were randomized to two ribociclib dosing schedules: 400 mg continuous vs 600 mg intermittent, with initiation in early (prior ET < 2 years) vs delayed (prior ET ≥ 2 years) setting.

TOP1 Mutations and Cross-Resistance to Antibody-Drug Conjugates in Patients with Metastatic Breast Cancer.

Purpose: Antibody-drug conjugates (ADC) harboring topoisomerase I (TOP1) inhibitor payloads have improved survival for patients with metastatic breast cancer. However, knowledge of ADC resistance mechanisms and potential impact on the sequential use of ADCs is limited. In this study, we report the incidence and characterization of TOP1 mutations arising in the setting of ADC resistance in metastatic breast cancer.

Abemaciclib Plus Fulvestrant in Advanced Breast Cancer After Progression on CDK4/6 Inhibition: Results From the Phase III postMONARCH Trial.

Purpose: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) are the standard first-line treatment for hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC); however, disease progression occurs in almost all patients and additional treatment options are needed. Herein, we report outcomes of the postMONARCH trial investigating a switch in ET with/without CDK4/6 inhibition with abemaciclib after disease progression on CDK4/6i.

Methods: This double-blind, randomized phase III study enrolled patients with disease progression on previous CDK4/6i plus aromatase inhibitor as initial therapy for advanced disease or recurrence on/after adjuvant CDK4/6i + ET.

Efficacy of Subsequent Treatments After Disease Progression on CDK4/6 Inhibitors in Patients With Hormone Receptor-Positive Advanced Breast Cancer.

Purpose: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) combined with endocrine therapy (ET) are the standard of care in hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (aBC). Yet, disease progression remains common. In the absence of established postprogression sequencing guidelines, we conducted a pooled analysis of Kaplan-Meier (KM)-derived patient data to assess the efficacy of subsequent treatment options after disease progression on CDK4/6i therapy.

Precision therapeutics and emerging strategies for HR-positive metastatic breast cancer.

Anti-oestrogen-based therapies, often combined with a CDK4/6 inhibitor, are the current standard-of-care first-line therapy for patients with advanced-stage hormone receptor-positive (HR) breast cancer. Resistance to anti-oestrogen agents inevitably occurs, mediated by oestrogen receptor (ER)-dependent or ER-independent mechanisms that drive tumour progression. Emerging endocrine therapies include, but are not limited to, next-generation oral ER degraders and proteolysis targeting chimeras, which might be particularly effective in patients with ESR1-mutant breast cancer.

VERITAC-2: a Phase III study of vepdegestrant, a PROTAC ER degrader, versus fulvestrant in ER+/HER2- advanced breast cancer.

Vepdegestrant (ARV-471) is an oral PROTAC ER degrader that binds an E3 ubiquitin ligase and ER to directly trigger ubiquitination of ER and its subsequent proteasomal degradation. In a first-in-human Phase I/II study, vepdegestrant monotherapy was well tolerated with clinical activity in pretreated patients with ER+/HER2- advanced breast cancer. The global, randomized Phase III VERITAC-2 study compares efficacy and safety of vepdegestrant versus fulvestrant in adults with ER+/HER2- advanced breast cancer after treatment with a CDK4/6 inhibitor plus endocrine therapy.

Mechanisms of sensitivity and resistance to CDK4/CDK6 inhibitors in hormone receptor-positive breast cancer treatment.

Cell cycle dysregulation is a hallmark of cancer that promotes eccessive cell division. Cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6) are key molecules in the G1-to-S phase cell cycle transition and are crucial for the onset, survival, and progression of breast cancer (BC). Small-molecule CDK4/CDK6 inhibitors (CDK4/6i) block phosphorylation of tumor suppressor Rb and thus restrain susceptible BC cells in G1 phase.

CDK4/6 Inhibitor Efficacy in -Mutant Metastatic Breast Cancer.

Background: In estrogen receptor-positive metastatic breast cancer, mutations (ESR1) are a common mechanism of acquired resistance to aromatase inhibitors (ArIh). However, the impact alterations have on CDK4/6 inhibitor (CDK4/6i) sensitivity has not been established. Analyses of CDK4/6i trials suggest that the endocrine therapy partner and specific allele may affect susceptibility.

Antibody-Drug Conjugate Sacituzumab Govitecan Enables a Sequential TOP1/PARP Inhibitor Therapy Strategy in Patients with Breast Cancer.

Purpose: The antibody-drug conjugate (ADC) sacituzumab govitecan (SG) comprises the topoisomerase 1 (TOP1) inhibitor (TOP1i) SN-38, coupled to a monoclonal antibody targeting trophoblast cell surface antigen 2 (TROP-2). Poly(ADP-ribose) polymerase (PARP) inhibition may synergize with TOP1i and SG, but previous studies combining systemic PARP and TOP1 inhibitors failed due to dose-limiting myelosuppression. Here, we assess the proof-of-mechanism and clinical feasibility for SG and talazoparib (TZP) employing an innovative sequential dosing schedule.

Cracking the Genomic Code of CDK4/6 Inhibitor Resistance.

The therapeutic approach to metastatic hormone receptor-positive, human epidermal growth factor-2-negative metastatic breast cancer (HR+/HER2- MBC) has evolved rapidly over recent years. The cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) have become first-line targeted agents of choice, in combination with an antiestrogen. Simultaneously, the clinical landscape of therapeutic options has been rapidly shifting, with novel antiestrogens, signal transduction inhibitors, and next-generation CDK inhibitors in various stages of development.

Virtual Molecular and Precision Medicine Clinic to Improve Access to Clinical Trials for Patients With Metastatic Breast Cancer: An Academic/Community Collaboration.

Purpose: There is a demand for improved care delivery surrounding genomic testing and clinical trial enrollment among patients with metastatic breast cancer (MBC). We sought to improve the current process via real-time informal consultation and prescreening assessment for patients with MBC treated by community and academic medical oncologists by implementing a virtual molecular and precision medicine (vMAP) clinic.

Methods: The vMAP program used a virtual referral system directed to a multidisciplinary team with precision medicine expertise.