INX-315, a Selective CDK2 Inhibitor, Induces Cell Cycle Arrest and Senescence in Solid Tumors

Cyclin-dependent kinase 2 (CDK2) is thought to play an important role in driving proliferation of certain cancers, including those harboring CCNE1 amplification and breast cancers that have acquired resistance to CDK4/6 inhibitors (CDK4/6i). The precise impact of pharmacologic inhibition of CDK2 is not known due to the lack of selective CDK2 inhibitors. Here we describe INX-315, a novel and potent CDK2 inhibitor with high selectivity over other CDK family members. Using cell-based assays, patient-derived xenografts (PDX), and transgenic mouse models, we show that INX-315 (i) promotes retinoblastoma protein hypophosphorylation and therapy-induced senescence (TIS) in CCNE1-amplified tumors, leading to durable control of tumor growth; (ii) overcomes breast cancer resistance to CDK4/6i, restoring cell cycle control while reinstating the chromatin architecture of CDK4/6i-induced TIS; and (iii) delays the onset of CDK4/6i resistance in breast cancer by driving deeper suppression of E2F targets. Our results support the clinical development of selective CDK2 inhibitors.

SIGNIFICANCE

INX-315 is a novel, selective inhibitor of CDK2. Our preclinical studies demonstrate activity for INX-315 in both CCNE1-amplified cancers and CDK4/6i-resistant breast cancer. In each case, CDK2 inhibition induces cell cycle arrest and a phenotype resembling cellular senescence. Our data support the development of selective CDK2 inhibitors in clinical trials. See related commentary by Watts and Spencer, p. 386. This article is featured in Selected Articles from This Issue, p. 384.

Overall Survival and Exploratory Biomarker Analyses of Abemaciclib plus Trastuzumab with or without Fulvestrant versus Trastuzumab plus Chemotherapy in HR+, HER2+ Metastatic Breast Cancer Patients

PURPOSE

The monarcHER trial has shown that abemaciclib, a cyclin-dependent kinase 4 and 6 inhibitor, combined with fulvestrant and trastuzumab, improves progression-free survival (PFS) in hormone receptor-positive (HR+), HER2-positive (HER2+) advanced breast cancer (ABC) compared with standard-of-care (SOC) chemotherapy combined with trastuzumab. We report the final overall survival (OS) analysis, updated safety and efficacy data, and exploratory biomarker results from monarcHER.

PATIENTS AND METHODS

monarcHER (NCT02675231), a randomized, multicenter, open-label, phase II trial, enrolled 237 patients across Arm A (abemaciclib, trastuzumab, fulvestrant), Arm B (abemaciclib, trastuzumab), and Arm C (SOC chemotherapy, trastuzumab). Following the statistical plan, OS and PFS were estimated in all arms. RNA sequencing (RNA-seq) was performed on archival tissue.

RESULTS

Median OS was 31.1 months in Arm A, 29.2 months in Arm B, and 20.7 months in Arm C [A vs. C: HR, 0.71; 95% confidence interval (CI), 0.48-1.05; nominal two-sided P value 0.086; B vs. C: HR 0.83 (95% CI, 0.57-1.23); nominal two-sided P value 0.365]. Updated PFS and safety findings were consistent with previous results. The most frequently reported treatment-emergent adverse events included diarrhea, fatigue, nausea, neutrophil count decrease, and anemia. In exploratory RNA-seq analyses, Luminal subtypes were associated with longer PFS [8.6 vs. 5.4 months (HR, 0.54; 95% CI, 0.38-0.79)] and OS [31.7 vs. 19.7 months (HR, 0.68; 95% CI, 0.46-1.00)] compared with non-Luminal.

CONCLUSIONS

In this phase II trial, abemaciclib + trastuzumab ± fulvestrant numerically improved median OS in women with HR+, HER2+ ABC compared with SOC chemotherapy + trastuzumab.

Abemaciclib plus trastuzumab with or without fulvestrant versus trastuzumab plus standard-of-care chemotherapy in women with HR+, HER2+ advanced breast cancer: plain language summary of the monarcHER study

WHAT IS THIS SUMMARY ABOUT?

This article summarizes the results of a study called monarcHER. The study included participants with a certain type of aggressive breast cancer called HR+, HER2+ advanced breast cancer (ABC) that had their disease worsen or return after multiple previous therapies. This summary intends to help you understand the impact of a non-chemotherapy treatment called abemaciclib in people with HR+, HER2+ ABC. When the study was planned, HER2-targeted therapy (ie trastuzumab) was standard treatment and was typically combined with chemotherapy and endocrine therapy (ie fulvestrant). However drug resistance can develop when HER2+ targeted therapy is used for a long time, making it less effective and allowing cancer to grow or spread to other parts of the body. When this happens, few chemotherapy-free options are available. Because of the chemotherapy side effects, this is not desirable. There is an urgent need to develop new, effective, safe, and tolerable treatment options for patients with HR+, HER2+ ABC. The monarcHER study compared the effects of abemaciclib plus trastuzumab with or without fulvestrant compared to the standard of care treatment.

WHAT WERE THE RESULTS?

Participants were randomly assigned to 1 of 3 groups: Group A (abemaciclib, trastuzumab and fulvestrant), Group B (abemaciclib and trastuzumab), or Group C (trastuzumab and standard of care chemotherapy). The study compared the length of time patients took study treatments without worsening or dying from their breast cancer. This is called the progression free survival (PFS). Participants in Group A had a longer median PFS than those in groups B and C (8.3 months, 5.7 months and 5.7 months respectively). There was no notable difference in PFS between participants in Groups B and C. Additionally, the study looked at the side effects with each treatment group. The most common side effect which is considered severe or lifethreatening was neutropenia, defined as decreased white blood cell levels. Neutropenia may lead to an increased risk of getting infections. However, the percentage of patients experiencing neutropenia was similar in all groups A, B and C (27%, 22% and 26%, respectively). Patients in groups A (79%) and B (78%) who received abemaciclib experienced similar rates of diarrhea.

WHAT DO THE RESULTS MEAN?

The data from the monarcHER study suggest that the combination of abemaciclib, trastuzumab, and fulvestrant may offer a chemotherapy-free option for patients with HR+, HER2+ ABC who have experienced worsening of disease despite multiple prior therapies.

Emerging Therapies for Breast Cancer

The steady, incremental improvements in outcomes for both early-stage and advanced breast cancer patients are, in large part, attributable to the success of novel systemic therapies. In this review, we discuss key conceptual paradigms that have underpinned this success including (1) targeting the driver: the identification and targeting of major oncoproteins in breast cancers; (2) targeting the lineage pathway: inhibition of those pathways that drive normal mammary epithelial cell proliferation that retain importance in cancer; (3) targeting precisely: the application of molecular classifiers to refine therapy selection for specific cancers, and of antibody-drug conjugates to pinpoint tumor and tumor promoting cells for eradication; and (4) exploiting synthetic lethality: leveraging unique vulnerabilities that cancer-specific molecular alterations induce. We describe promising examples of novel therapies that have been discovered within each of these paradigms and suggest how future drug development efforts might benefit from the continued application of these principles.

Abstract 5994: INX-315, a potent and selective CDK2 inhibitor, demonstrates robust antitumor activity in CCNE1-amplified cancers

Cyclin-dependent kinases (CDK) are a family of serine/threonine kinases that heterodimerize with regulatory subunits called cyclins to drive cell cycle progression. Uncontrolled cellular proliferation is a hallmark of cancer commonly driven by dysregulated kinase activity of specific CDK family members, including cyclin-dependent kinase 2 (CDK2). Aberrant CDK2 activity most frequently occurs through amplification of CCNE1 and/or overexpression of its protein product cyclin E1, which is a canonical binding partner of CDK2. Overexpression of cyclin E1 is observed in many solid tumors including in patients with high grade serous ovarian cancer (HGSOC), gastric cancer, and ER-positive breast cancer patients whose tumors have progressed on a prior CDK4/6 inhibitor regimen. Selective inhibition of CDK2 is thus a compelling therapeutic approach to regain cell cycle control. Here, we report preclinical data supporting the development of INX-315 for patients with cancers in which proliferation is CDK2-dependent. INX-315 is a potent inhibitor of CDK2/cyclin E (0.6 nM biochemical IC50) with high selectivity over other CDK family members in both biochemical and intracellular NanoBRET assays. In CCNE1-amplified human ovarian and gastric cancer cell lines, INX-315 potently inhibited Rb phosphorylation, induced a G1 cell cycle arrest, and inhibited proliferation. INX-315 also showed potent anti-proliferative activity in luminal breast cancer cell lines that had been cultured in CDK4/6 inhibitor (+/- anti-estrogen therapy) for prolonged periods to the point of developing drug resistance. While these cell lines did not readily respond to either CDK4/6 or CDK2 inhibition alone, combination treatment again suppressed Rb phosphorylation, accompanied by G1 arrest and a senescent-like phenotype. Lastly, in CCNE1-amplified xenograft models of ovarian and gastric carcinomas, INX-315 inhibited Rb-phosphorylation and induced tumor regression. These data demonstrate INX-315 to be a potent and selective CDK2 inhibitor that may benefit patients with CDK2/cyclin E driven cancers.

Citation Format: Alec G. Trub, John E. Bisi, Catherine Dietrich, Michael Taylor, Jay C. Strum, Shom Goel, Patrick J. Roberts. INX-315, a potent and selective CDK2 inhibitor, demonstrates robust antitumor activity in CCNE1-amplified cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5994.

PD-1 blockade and CDK4/6 inhibition augment nonoverlapping features of T cell activation in cancer

We performed single-cell RNA-sequencing and T cell receptor clonotype tracking of breast and ovarian cancer patients treated with the CDK4/6 inhibitor ribociclib and PD-1 blockade. We highlight evidence of two orthogonal treatment-associated phenomena: expansion of T cell effector populations and promotion of T cell memory formation. Augmentation of the antitumor memory pool by ribociclib boosts the efficacy of subsequent PD-1 blockade in mouse models of melanoma and breast cancer, pointing toward sequential therapy as a potentially safe and synergistic strategy in patients.

Abstract P3-06-03: Trilaciclib induces immune changes within the tumor microenvironment in early-stage triple-negative breast cancer

Background: In early-stage triple-negative breast cancer (TNBC), there is accumulating evidence of a correlation between tumor-infiltrating lymphocytes in tumor tissue and favorable clinical outcomes, with a high CD8+/regulatory T-cell (Treg) ratio after neoadjuvant chemotherapy being predictive of overall survival and associated with pathologic complete response (Ladoire S, et al. Br J Cancer. 2011; Park YH, et al. Nat Commun. 2020). Trilaciclib is a transient inhibitor of cyclin-dependent kinase 4/6 that is administered intravenously prior to chemotherapy. In preclinical studies, trilaciclib has been shown to have immune-enhancing effects by differentially arresting CD8+ T-cell and Treg subsets, which is followed by the faster recovery of CD8+ T cells than Tregs in the tumor microenvironment. Methods: This phase 2, single-arm, open-label study aims to evaluate neoadjuvant, single-dose trilaciclib followed by trilaciclib plus dose-dense anthracycline/cyclophosphamide and taxane in patients with early-stage TNBC (NCT05112536). Patients with previously untreated, non-metastatic, confirmed TNBC and a primary tumor ≥ 1.5 cm of any nodal status receive a single dose of trilaciclib 240 mg/m2 during the lead-in phase, followed by 4 cycles of doxorubicin 60 mg/m2 plus cyclophosphamide 600 mg/m2, and 12 weekly cycles of paclitaxel 80 mg/m2. Trilaciclib 240 mg/m2 is administered prior to the first chemotherapy dose of each cycle. Pembrolizumab 400 mg every 6 weeks starting on day 1, cycle 1, and/or carboplatin AUC 1.5 every week starting on day 1, cycle 5, is allowed per investigator discretion. Tumor biopsies and peripheral blood samples are collected prior to any treatment, 7 days ± 1 day post administration of trilaciclib, and during surgery, with an additional blood sample collection on day 1, cycle 2. The primary objective is to evaluate the immune-based mechanism of action of trilaciclib after a single dose of trilaciclib, as measured by changes in the CD8+/Treg ratio in tumor tissue. Pathologic complete response, safety and tolerability, and additional exploratory immune biomarker endpoints will also be assessed. Results: As of June 3, 2022, 9 patients with early-stage TNBC had been enrolled and 8 patients had received the trilaciclib lead-in dose and initiated doxorubicin/cyclophosphamide. Patients had a median age of 53.0 years, and all had stage II tumors at diagnosis, with 7 having ductal carcinoma. The median number of chemotherapy cycles received was 3 (range 1–6), and all 8 patients received pembrolizumab. Seven patients continue study treatment; 1 patient discontinued due to disease progression. Five patients had an adverse event (AE) related to any study treatment, including 4 patients with ≥ 1 trilaciclib-related AE. There were no grade ≥ 3 treatment-related AEs or serious AEs. On-treatment, post-trilaciclib monotherapy biopsies were available for 4 patients. Following neoadjuvant trilaciclib treatment, the median density of stromal CD8+ T cells increased from 103.1/mm2 at baseline to 229.8/mm2 at day 7. The median CD8+/Treg ratio increased in 2 patients from 1.85 at baseline to 1.90 at day 7. Conclusions: Preliminary analysis of on-treatment tumor biopsies from 4 patients suggests that a single dose of trilaciclib may modulate the immune cell composition in the tumor microenvironment to support antitumor immune responses. The increase in CD8+ T cells following 7-day neoadjuvant treatment with trilaciclib supports previous data suggesting a role in T-cell infiltration. The complete dataset from all patients (estimated enrollment: N ≈ 24) and additional biomarker analyses will be presented.

Citation Format: Michael Danso, Joyce O’Shaughnessy, Lisa S. Wang, Kailash Mosalpuria, Sara Hurvitz, Shom Goel, Sarah Ahn, Subing Cao, John S. Yi, Taofik Oyekunle, Amanda Jacobson, Andrew Beelen, Jeremy Force. Trilaciclib induces immune changes within the tumor microenvironment in early-stage triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-06-03.

Abstract PD13-09: PD13-09 Clinical outcomes of patients with HR+ HER2- advanced breast cancer with early progression on CDK4/6 inhibitors

Background: CDK4/6 inhibitors (CDK4/6i) paired with endocrine therapy (ET) are considered first-line (1L) therapy for patients (pts) with HR+ HER2- advanced breast cancer (aBC). A minority of pts will demonstrate primary resistance to CDK4/6i, as characterized by early progression. Thymidine kinase 1 (TK1) is a cell-cycle regulated enzyme downstream of CDK4/6 and involved in nucleotide metabolism during DNA synthesis. Prior studies have shown TK1 may serve as a biomarker of response to CDK4/6i, with early TK1 activity (TK1a) suppression after initiation of CDK 4/6i therapy associated with improved PFS. Lack of TK1a suppression may be associated with primary resistance to CDK4/6i. In this study, we aim to analyze response to subsequent lines of therapy and overall survival (OS) of pts with early progression on 1L CDK4/6i. Methods: Pts with HR+ HER2- aBC from a phase II trial of an alternative schedule of palbociclib (palbo alt dosing trial NCT 3007979) and from a retrospective palbociclib study were included in this analysis. Pts in the palbo alt dosing trial underwent baseline and C1D15 TK1a analysis after initiation on CDK4/6i. C1D15 TK1a suppression was defined at TK1a < 30 Du/L. Pts in the retrospective palbociclib study included pts receiving palbo as part of their standard of care 1L therapy for HR+ HER2- aBC at Washington University in Saint Louis from 2016 to 2021. Clinical information, including treatment start and stop dates on each of the next-line therapies, were collected from the electronic medical record. PFS was estimated by the treatment duration on a specified treatment regimen. Early progression on CDK4/6i was defined as PFS < 6 mo. Best response was defined as next line of therapy with the numerically longest PFS. OS was defined as time to death from the initiation of CDK4/6i. Results: Of the 54 pts enrolled on the palbo alt dosing trial, 51 pts were evaluable for clinical benefit and 46 pts were evaluable for TK1a suppression rate at C1D15. 7 pts (15.2%) were found without TK1a suppression at C1D15. This lack of TK1a suppression on palbo was associated with a significantly shorter PFS (median PFS=3.1 mo) compared to not reached in pts with TK1a suppression at C1D15. We conducted clinical analysis on N=26 pts who exhibited early progression on CDK4/6i which included 10 pts from the palbo alt dosing trial and 16 from the retrospective study. The average subsequent line of therapies in this cohort was 3, with the most common second line (2L) therapy being chemotherapy (N=17, 65.4%) and ET (N=8, 30.8%). The median PFS for pts receiving 2L chemotherapy and ET was 4.09 mo and 3.64 mo, respectively. 10 pts received both chemotherapy and ET with 7 (70.0%) achieving best response with chemotherapy compared to 3 pts (30.0%) who achieved best response with ET. The median OS for the cohort was 14.6 mo. Conclusions: Early progression on CDK4/6i is associated with a particularly poor prognosis. In our cohort, the median OS was far below the expected median OS for pts receiving 1L palbo as reported in the PALOMA-2 trial (14.6 mo vs 53.9 mo). Early progression on CDK4/6i is associated with more aggressive disease which may respond more favorably to chemotherapy, as demonstrated by best response to therapy. Further prospective studies are warranted to explore this treatment approach.

Citation Format: Katherine K. Clifton, Shana N. Thomas, Jingqin Luo, Jing Xi, Nusayba A. Bagegni, Foluso O. Ademuyiwa, Rama Suresh, Ashley Frith, Andrew A. Davis, Ron Bose, Katherine Weilbaecher, Whitney L. Hensing, Timothy Pluard, Massimo Cristofanilli, Hyo S. Han, Adam M. Brufsky, Kevin Kalinsky, Shom Goel, Seth A. Wander, Lindsay L. Peterson, Cynthia Ma. PD13-09 Clinical outcomes of patients with HR+ HER2- advanced breast cancer with early progression on CDK4/6 inhibitors [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD13-09.

HepCCATT: a multilevel intervention for hepatitis C among vulnerable populations in Chicago

BACKGROUND

Hepatitis C infection could be eliminated. Underdiagnosis and lack of treatment are the barriers to cure, especially for vulnerable populations (i.e. unable to pay for health care).

METHODS

A multilevel intervention from September 2014 to September 2019 focused on the providers and organizations in 'the safety net' (providing health care to populations unable to pay), including: (i) public education, (ii) training for primary care providers (PCPs) and case managers, (iii) case management for high-risk populations, (iv) policy advice and (v) a registry (Registry) for 13 health centers contributing data. The project tracked the number of PCPs trained and, among Registry sites, the number of people screened, engaged in care (i.e. clinical follow-up after diagnosis), treated and/or cured.

RESULTS

In Chicago, 215 prescribing PCPs and 56 other health professionals, 86% of whom work in the safety net, were trained to manage hepatitis C. Among Registry sites, there was a 137% increase in antibody screening and a 32% increase in current hepatitis C diagnoses. Engagement in care rose by 18%.

CONCLUSIONS

Hepatitis C Community Alliance to Test and Treat (HepCCATT) successfully targeted safety net providers and organizations with a comprehensive care approach. While there were challenges, HepCCATT observed increased hepatitis C screening, diagnosis and engagement in care in the Chicago community.

Fractional flow reserve versus angiography guided revascularization for patients with multivessel coronary artery disease: a systematic review and meta-analysis of randomized controlled trials

Background

Recently published randomized controlled trials (RCT) have questioned the utility of Fraction Flow Reserve (FFR) to guide revascularization in patients with multivessel coronary artery disease (CAD) as compared to Angiography

Purpose

This current analysis aimed to compare the clinical outcomes associated with FFR guided versus standard angiography-guided revascularization for patients with multivessel CAD using a large number of randomized patients with stable CAD and acute coronary syndrome (ACS)

Methods

We conducted an electronic database search of all published data for RCT that compared FFR versus Angiography for patients with multivessel CAD and reported on subsequent mortality, cardiac death, myocardial infarction, revascularization, and other outcomes of interest. Event rates were compared using a forest plot of odds ratios using a fixed-effects model assuming interstudy heterogeneity.

Results

Eleven RCT (n=6052; FFR = 3043, Angiography = 3027) were included in the final analysis. Mean follow-up period was 1.7 years. In our analysis, FFR guided revascularization as compared to angiography guided revascularization alone was not associated with any significant reduction in overall mortality (OR = 1.10, 95% CI = 0.83–1.47, P=0.47, I2=0), cardiac mortality (OR = 0.95, 95% CI = 0.63–1.45, P=0.42, I2=0), all revascularization (OR = 0.96, 95% CI = 0.80–1.14, P=0.17, I2=31%) or myocardial infarction (OR = 0.99, 95% CI = 0.79–1.23, P=0.33, I2=12%). There was also no difference between two groups in terms of major adverse cardiac or cerebrovascular event [MACCE] (OR = 1.13, 95% CI = 0.90–1.42, P=0.39, I2=5%), major adverse cardiac event [MACE] (OR = 0.86, 95% CI = 0.70–1.07, P=0.55, I2=0), stroke/TIA (OR = 1.61, 95% CI = 0.92–2.82, P=0.36, I2=8%) or target lesion revascularization [TLR] (OR = 0.86, 95% CI = 0.44–1.67, P=0.71, I2=0). Furthermore, sensitivity analysis was conducted to include only studies with ACS patients and studies which used CABG only for revascularization. However, there was no difference between the two groups for any of the above outcomes

Conclusion

There is no difference in clinical outcomes in patients undergoing FFR-guided versus angiography guided revascularization for multivessel CAD

Funding Acknowledgement

Type of funding sources: None.

Trilaciclib prior to gemcitabine plus carboplatin for metastatic triple-negative breast cancer: phase III PRESERVE 2

Triple-negative breast cancer (TNBC) is an aggressive malignancy for which cytotoxic chemotherapy remains the backbone of treatment. Trilaciclib is an intravenous cyclin-dependent kinase 4/6 inhibitor that induces transient cell cycle arrest of hematopoietic stem and progenitor cells and immune cells during chemotherapy exposure, protecting them from chemotherapy-induced damage and enhancing immune activity. Administration of trilaciclib prior to gemcitabine plus carboplatin (GCb) significantly improved overall survival (OS) compared with GCb alone in an open-label phase II trial in patients with metastatic TNBC, potentially through protection and direct activation of immune function. The randomized, double-blind, placebo-controlled, phase III PRESERVE 2 trial will evaluate the efficacy and safety of trilaciclib administered prior to GCb in patients with locally advanced unresectable or metastatic TNBC. Clinical Trial Registration: NCT04799249 (ClinicalTrials.gov).

Targeting CDK4 and 6 in Cancer Therapy: Emerging Preclinical Insights Related to Abemaciclib

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4 and 6) are approved for the treatment of subsets of patients with hormone receptor positive (HR+) breast cancer (BC). In metastatic disease, strategies involving endocrine therapy combined with CDK4 and 6 inhibitors (CDK4 and 6i) improve clinical outcomes in HR+ BCs. CDK4 and 6i prevent retinoblastoma tumor suppressor protein phosphorylation, thereby blocking the transcription of E2F target genes, which in turn inhibits both mitogen and estrogen-mediated cell proliferation. In this review, we summarize preclinical data pertaining to the use of CDK4 and 6i in BC, with a particular focus on several of the unique chemical, pharmacologic, and mechanistic properties of abemaciclib. As research efforts elucidate the novel mechanisms underlying abemaciclib activity, potential new applications are being identified. For example, preclinical studies have demonstrated abemaciclib can exert antitumor activity against multiple tumor types and can cross the blood-brain barrier. Abemaciclib has also demonstrated distinct activity as a monotherapeutic in the treatment of BC. Accordingly, we also discuss how a greater understanding of mechanisms related to CDK4 and 6 blockade highlight abemaciclib's unique in-class properties, and could pave new avenues for enhancing its therapeutic efficacy.

Role of oxidative stress in angiogenesis and the therapeutic potential of antioxidants in breast cancer

The escalation of cancer cases globally, especially breast cancer, is of concern. Angiogenesis is hallmark of cancer pathogenesis and plays an important role in cancer progression and metastasis. Pro-angiogenic agents, secreted by tumor cells, form new blood vessels, and produce reactive oxygen species (ROS). ROS promote angiogenesis via two major pathways: namely Vascular Endothelial Growth Factor (VEGF) dependent and non-VEGF dependent pathways. As a consequence of unbalanced ROS overproduction and low antioxidants levels, oxidative stress occurs and promotes angiogenesis in breast cancer tissues. Thus, the potential use of antioxidants as a preventive therapy in breast cancer. Preclinical studies depict that vitamins A and E may counter oxidative stress resulting in reduction of metastasis and viability of breast cancer. Furthermore, clinical studies demonstrate a decline in breast cancer risk in postmenopausal women upon the consumption of antioxidants. Herein, we discuss various pro-angiogenic agents that may play an important role in breast cancer angiogenesis. Moreover, the contribution of oxidative stress in inducing the angiogenic process is extensively reviewed here. Furthermore, the findings of pre-clinical and clinical studies on the use of antioxidants, namely vitamins A and E, in breast cancer are deliberated upon, along with the role of angiogenesis in cancer therapy.

Targeting CDK4 and CDK6 in cancer

Cyclin-dependent kinase 4 (CDK4) and CDK6 are critical mediators of cellular transition into S phase and are important for the initiation, growth and survival of many cancer types. Pharmacological inhibitors of CDK4/6 have rapidly become a new standard of care for patients with advanced hormone receptor-positive breast cancer. As expected, CDK4/6 inhibitors arrest sensitive tumour cells in the G1 phase of the cell cycle. However, the effects of CDK4/6 inhibition are far more wide-reaching. New insights into their mechanisms of action have triggered identification of new therapeutic opportunities, including the development of novel combination regimens, expanded application to a broader range of cancers and use as supportive care to ameliorate the toxic effects of other therapies. Exploring these new opportunities in the clinic is an urgent priority, which in many cases has not been adequately addressed. Here, we provide a framework for conceptualizing the activity of CDK4/6 inhibitors in cancer and explain how this framework might shape the future clinical development of these agents. We also discuss the biological underpinnings of CDK4/6 inhibitor resistance, an increasingly common challenge in clinical oncology.

Cellular mechanisms underlying response and resistance to CDK4/6 inhibitors in the treatment of hormone receptor-positive breast cancer

Pharmacological inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) are now an established standard of care for patients with advanced hormone receptor-positive breast cancer. The canonical mechanism underlying CDK4/6 inhibitor activity is the suppression of phosphorylation of the retinoblastoma tumor suppressor protein, which serves to prevent cancer cell proliferation. Recent data suggest that these agents induce other diverse effects within both tumor and stromal compartments, which serve to explain aspects of their clinical activity. Here, we review these phenomena and discuss how they might be leveraged in the development of novel CDK4/6 inhibitor-containing combination treatments. We also briefly review the various known mechanisms of acquired resistance in the clinical setting.

Abstract OT2-19-01: Presurgical treatment with ribociclib and letrozole in patients with locally advanced breast cancer: The NEOLETRIB study

Background: The introduction of CDK4/6 inhibitors has been one of the most pivotal breakthroughs in breast cancer therapy in recent decades. A growing body of evidence now suggests that novel targeting inhibitors of CDK4/6, as well as MAPK and PI3K inhibitors, might have anti-tumor effects beyond tumour cell cytostasis, including immunomodulation. Specifically, studies have demonstrated that CDK4/6 inhibitors can have immunogenic effects, through the induction of a senescent-like phenotype in tumor cells, changes in tumor cell metabolism, and direction modulation of T cell function. Trial design: NEOLETRIB is a multicenter, single-arm, open-label, neoadjuvant, phase II trial. Eligibility criteria: Patients suffering from locally advanced breast cancer defined as either large T2 (> 3 cm), or T3/T4, and/or N2-3 are suitable for inclusion. Both, luminal-A and luminal-B tumors are allowed. HER-2 positive and triple-negative patients are excluded from this trial, as are patients with patients with evidence of distant metastasis. Treatment: All patients receive neoadjuvant therapy for at least 6 months with ribociclib (600 mg daily, 21 days on/7 days off) and letrozole (2.5 mg daily). Premenopausal women will also receive goserelin (3.6 mg s.c. every 28 days) according to clinical practice. Specific aims: The primary objective is to evaluate the intra-tumor immunological effects in individual patients treated with letrozole and ribociclib in the neoadjuvant setting. Secondary objectives include evaluation of clinical and pathological response to the treatment combination, identification of early and late molecular mechanisms of treatment adaptation and resistance, and investigation of the effects of the treatment on the gut microbiota and vice versa. As an exploratory objective, we aim to study the relationship between cancer treatment effects, the immune competent cells in the blood and the gut microbiota. Long-term follow-up will continue after the primary analysis for up to 10 years or until death, withdrawal of consent, loss to follow-up, or trial closure. To allow for the planned laboratory sub-studies, tumor tissue biopsies, blood and stool samples will be collected at baseline, day 21 and at time of surgery, with additional blood and stool samples collected at day 90. The samples will be analyzed to evaluate and measure numerous parameters including levels of cytokines and metabolites, cell free DNA-fragments, and intra-tumor gene expression/regulation using state of the art laboratory methods together with international collaborators. Advanced MRI-techniques are used at baseline and following 3 and 6 months on treatment for clinical efficacy measurements in the breast. Statistical methods: Due to the nature of this single-arm study with longitudinal sampling from individual patients, the statistics will be descriptive in nature, focusing on intra-patient comparisons over time. The inclusion goal of 100 patients is based on the response rate of neoadjuvant trials with ribociclib to allow for a minimum of 30 patients in the responder & non-responder arms, which is sufficient for hypothesis generating results. Present accrual and target accrual: Following 8 weeks after initiation of this trial, the first 10 patients have been enrolled. The target accrual is 100 patients with complete study procedures.

Citation Format: Xavier Tekpli, Shom Goel, Barbro Holm, Lars-Egil Fallang, Laurens Cornelus Reitsma, Stephanie Beate Geisler, Hilde Presterud Ødegård, Cathrine Bergquist Fosskaug, Ida Caroline Lindem, Manouchehr Seyedzadeh, Jonn Terje Geitung, Joana Reis, Kjell Inge Gjesdal, Unn-Cathrin Buvarp, Marie Loeng, Kristine Kleivi Sahlberg, Alina Carmen Porojnicu, Helle Kristine Skjerven, Andliena Tahiri, Shakila Jabeen, Torben Lüders, Vahid Bemanian, Jørgen Jahnsen, Marianne Lyngra, Antoni Hurtado, Jason Carroll, Shiuan Chen, Vessela Kristensen, Jürgen Geisler. Presurgical treatment with ribociclib and letrozole in patients with locally advanced breast cancer: The NEOLETRIB study [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-19-01.

Asymptomatic infection and transmission of COVID-19 among clusters: systematic review and meta-analysis

OBJECTIVES

Countries throughout the world are experiencing COVID-19 viral load in their populations, leading to potential transmission and infectivity of asymptomatic COVID-19 cases. The current systematic review and meta-analysis aims to investigate the role of asymptomatic infection and transmission reported in family clusters, adults, children and health care workers, globally.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

An online literature search of PubMed, Google Scholar, medRixv and BioRixv was performed using standard Boolean operators and included studies published up to 17 August 2021. For the systematic review, case reports, short communications and retrospective studies were included to ensure sufficient asymptomatic COVID-19 transmission data were reported. For the quantitative synthesis (meta-analysis), participant data from a collection of cohort studies focusing on groups of familial clusters, adults, children and health care workers were included. Inconsistency among studies was assessed using I² statistics. The data synthesis was computed using the STATA 16.0 software.

RESULTS

This study showed asymptomatic transmission among familial clusters, adults, children and health care workers of 15.72%, 29.48%, 24.09% and 0%, respectively. Overall, asymptomatic transmission was 24.51% (95% confidence interval [CI]: 14.38, 36.02) among all studied population groups, with a heterogeneity of I² = 95.30% (P < 0.001). No heterogeneity was seen in the population subgroups of children and health care workers. The risk of bias in all included studies was assessed using the Newcastle Ottawa Scale.

CONCLUSIONS

For minimising the spread of COVID-19 within the community, this study found that following the screening of asymptomatic cases and their close contacts for chest CT scan (for symptomatic patients), even after negative nucleic acid testing, it is essential to perform a rigorous epidemiological history, early isolation, social distancing and an increased quarantine period (a minimum of 14-28 days). This systematic review and meta-analysis supports the notion of asymptomatic COVID-19 infection and person-to-person transmission and suggests that this is dependent on the varying viral incubation period among individuals. Children, especially those of school age (i.e. <18 years), need to be monitored carefully and follow mitigation strategies (e.g. social distancing, hand hygiene, wearing face masks) to prevent asymptomatic community transmission of COVID-19.

Early on-treatment transcriptional profiling as a tool for improving pathological response prediction in HER2-positive inflammatory breast cancer

Background

Inflammatory breast cancer (IBC) is a rare and understudied disease, with 40% of cases presenting with human epidermal growth factor receptor 2 (HER2)-positive subtype. The goals of this study were to (i) assess the pathologic complete response (pCR) rate of short-term neoadjuvant dual-HER2-blockade and paclitaxel, (ii) contrast baseline and on-treatment transcriptional profiles of IBC tumor biopsies associated with pCR, and (iii) identify biological pathways that may explain the effect of neoadjuvant therapy on tumor response.

Patients and Methods

A single-arm phase II trial of neoadjuvant trastuzumab (H), pertuzumab (P), and paclitaxel for 16 weeks was completed among patients with newly diagnosed HER2-positive IBC. Fresh-frozen tumor biopsies were obtained pretreatment (D1) and 8 days later (D8), following a single dose of HP, prior to adding paclitaxel. We performed RNA-sequencing on D1 and D8 tumor biopsies, identified genes associated with pCR using differential gene expression analysis, identified pathways associated with pCR using gene set enrichment and gene expression deconvolution methods, and compared the pCR predictive value of principal components derived from gene expression profiles by calculating and area under the curve for D1 and D8 subsets.

Results

Twenty-three participants were enrolled, of whom 21 completed surgery following neoadjuvant therapy. Paired longitudinal fresh-frozen tumor samples (D1 and D8) were obtained from all patients. Among the 21 patients who underwent surgery, the pCR and the 4-year disease-free survival were 48% (90% CI 0.29-0.67) and 90% (95% CI 66-97%), respectively. The transcriptional profile of D8 biopsies was found to be more predictive of pCR (AUC = 0.91, 95% CI: 0.7993-1) than the D1 biopsies (AUC = 0.79, 95% CI: 0.5905-0.9822).

Conclusions

In patients with HER2-positive IBC treated with neoadjuvant HP and paclitaxel for 16 weeks, gene expression patterns of tumor biopsies measured 1 week after treatment initiation not only offered different biological information but importantly served as a better predictor of pCR than baseline transcriptional analysis.

Trial Registration

ClinicalTrials.gov identifier: NCT01796197 (https://clinicaltrials.gov/ct2/show/NCT01796197); registered on February 21, 2013.

The tale of TILs in breast cancer: A report from The International Immuno-Oncology Biomarker Working Group

The advent of immune-checkpoint inhibitors (ICI) in modern oncology has significantly improved survival in several cancer settings. A subgroup of women with breast cancer (BC) has immunogenic infiltration of lymphocytes with expression of programmed death-ligand 1 (PD-L1). These patients may potentially benefit from ICI targeting the programmed death 1 (PD-1)/PD-L1 signaling axis. The use of tumor-infiltrating lymphocytes (TILs) as predictive and prognostic biomarkers has been under intense examination. Emerging data suggest that TILs are associated with response to both cytotoxic treatments and immunotherapy, particularly for patients with triple-negative BC. In this review from The International Immuno-Oncology Biomarker Working Group, we discuss (a) the biological understanding of TILs, (b) their analytical and clinical validity and efforts toward the clinical utility in BC, and (c) the current status of PD-L1 and TIL testing across different continents, including experiences from low-to-middle-income countries, incorporating also the view of a patient advocate. This information will help set the stage for future approaches to optimize the understanding and clinical utilization of TIL analysis in patients with BC.

New era of education: mobile learning of coronary guidewires in cardiovascular medicine

Background

Online education has transformed the way we teach and learn, especially in the midst of a global pandemic. Multiple devices, including coronary guidewires, are required to perform a successful coronary intervention, and understanding the engineering aspect of coronary guidewire technology is paramount.

Purpose

We aim to develop and evaluate a novel teaching tool/mobile learning app to understand a complex guidewire architecture and appropriate wire selection based on a lesion characteristics.

Methods

A guidewire is incredibly complex, consisting of a multitude of technologies allowing a range of tip softness, trackability around curves, and precise torque control. Despite operator preference, the process of choosing an appropriate coronary guidewire has gone mostly unchanged. We envisioned developing the GuidewireAID app with three main parts: 1) wire basics, 2) lesion-based guidewire selection, and 3) cased-based approach. Appropriate teaching cases were selected from a large-volume catheterization laboratory and divided into non-chronic total occlusion (non-CTO) and CTO. Non-CTO cases include simple, calcified, angulated, and bifurcation lesions, as well as thrombotic occlusion and tortuous vessels (Figure 1). Each case is described and analysis is offered on how to select an appropriate wire, followed by teaching points pertinent to the topic.

Results

Twenty-three detailed clinical cases and more than a hundred wires are illustrated in the GuidewireAID app. Case presentation, angiographic analysis, and a thorough understanding of wire characteristics allows the operator to know which wire to use and when it is time to switch, especially when dealing with complex coronary cases.

Conclusion

The GuidewireAID app will help fellows in training (FIT), early career interventionists, and practicing interventional cardiologists understand the complex aspects of a coronary guidewire and appreciate how their nuances could overcome real-world clinical challenging scenarios.

Funding Acknowledgement

Type of funding sources: None. Figure 1

Inhibition of CDK4/6 Promotes CD8 T-cell Memory Formation

CDK4/6 inhibitors are approved to treat breast cancer and are in trials for other malignancies. We examined CDK4/6 inhibition in mouse and human CD8+ T cells during early stages of activation. Mice receiving tumor-specific CD8+ T cells treated with CDK4/6 inhibitors displayed increased T-cell persistence and immunologic memory. CDK4/6 inhibition upregulated MXD4, a negative regulator of MYC, in both mouse and human CD8+ T cells. Silencing of Mxd4 or Myc in mouse CD8+ T cells demonstrated the importance of this axis for memory formation. We used single-cell transcriptional profiling and T-cell receptor clonotype tracking to evaluate recently activated human CD8+ T cells in patients with breast cancer before and during treatment with either palbociclib or abemaciclib. CDK4/6 inhibitor therapy in humans increases the frequency of CD8+ memory precursors and downregulates their expression of MYC target genes, suggesting that CDK4/6 inhibitors in patients with cancer may augment long-term protective immunity. SIGNIFICANCE: CDK4/6 inhibition skews newly activated CD8+ T cells toward a memory phenotype in mice and humans with breast cancer. CDK4/6 inhibitors may have broad utility outside breast cancer, particularly in the neoadjuvant setting to augment CD8+ T-cell priming to tumor antigens prior to dosing with checkpoint blockade.This article is highlighted in the In This Issue feature, p. 2355.

Best Practices for Spatial Profiling for Breast Cancer Research with the GeoMx® Digital Spatial Profiler

Breast cancer is a heterogenous disease with variability in tumor cells and in the surrounding tumor microenvironment (TME). Understanding the molecular diversity in breast cancer is critical for improving prediction of therapeutic response and prognostication. High-plex spatial profiling of tumors enables characterization of heterogeneity in the breast TME, which can holistically illuminate the biology of tumor growth, dissemination and, ultimately, response to therapy. The GeoMx Digital Spatial Profiler (DSP) enables researchers to spatially resolve and quantify proteins and RNA transcripts from tissue sections. The platform is compatible with both formalin-fixed paraffin-embedded and frozen tissues. RNA profiling was developed at the whole transcriptome level for human and mouse samples and protein profiling of 100-plex for human samples. Tissue can be optically segmented for analysis of regions of interest or cell populations to study biology-directed tissue characterization. The GeoMx Breast Cancer Consortium (GBCC) is composed of breast cancer researchers who are developing innovative approaches for spatial profiling to accelerate biomarker discovery. Here, the GBCC presents best practices for GeoMx profiling to promote the collection of high-quality data, optimization of data analysis and integration of datasets to advance collaboration and meta-analyses. Although the capabilities of the platform are presented in the context of breast cancer research, they can be generalized to a variety of other tumor types that are characterized by high heterogeneity.

Phase 1b clinical trial of ado-trastuzumab emtansine and ribociclib for HER2-positive metastatic breast cancer

Patients with HER2+ metastatic breast cancer are often treated with a multitude of therapies in the metastatic setting, and additional strategies to prolong responses to anti-HER2 therapies are needed. Preclinical evidence suggests synergy between cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors and anti-HER2 therapies. We conducted a phase 1b study of ribociclib and ado-trastuzumab emtansine (T-DM1) in patients with advanced/metastatic HER2-positive breast cancer previously treated with trastuzumab and a taxane in any setting, with four or fewer prior lines of therapy in the metastatic setting. A standard 3 + 3 dose-escalation design was used to evaluate various doses of ribociclib in combination with T-DM1, starting at 300 mg. The primary objective was to determine the maximum tolerated dose and/or recommended phase 2 dose (RP2D) of ribociclib in combination with T-DM1. A total of 12 patients were enrolled. During dose-escalation, patients received doses of ribociclib of 300 mg (n = 3), 400 mg (n = 3), 500 mg (n = 3), and 600 mg (n = 3). No dose-limiting toxicities were observed. The majority of toxicities were Grade 1 and 2, and the most common Grade 3 toxicities were neutropenia (33%), leukopenia (33%), and anemia (25%). After a median follow-up of 12.4 months, the median PFS was 10.4 months (95% confidence interval, 2.7-19.3). Based on the pharmacokinetic analysis, adverse events, and dose reductions, 400 mg was determined to be the RP2D for ribociclib given on days 8-21 of a 21-day cycle with T-DM1.

eMonarcHER: A phase 3 study of abemaciclib plus standard adjuvant endocrine therapy in patients with HR+, HER2+, node-positive, high-risk early breast cancer

TPS596

Background: Hormone receptor positive (HR+), human epidermal growth factor receptor 2-positive (HER2+) breast cancer (BC) with high-risk characteristics has a high risk of disease recurrence. Novel therapeutic options for this population are urgently needed. Abemaciclib is an oral, selective, and potent CDK4 & 6 inhibitor administered on a continuous schedule which is approved for HR+, HER2- advanced BC (ABC) as monotherapy and in combination with endocrine therapy (ET). Abemaciclib combined with ET demonstrated a statistically significant improvement in invasive disease-free survival (IDFS) in participants (pt) with HR+, HER2-, node-positive, high risk early breast cancer (EBC) and also clinical activity in HR+, HER2+ ABC. The eMonarcHER trial investigates whether abemaciclib plus ET will improve IDFS in pts with HR+, HER2+, node-positive, high risk EBC. Methods: eMonarcHER is a phase 3 global, randomized, double-blinded, placebo (PB)-controlled trial in participants with HR+, HER2+, node-positive, high risk EBC who have completed adjuvant HER2-targeted therapy (tx). Eligible participants are randomized 1:1 to receive either abemaciclib 150 mg twice daily or PB, plus standard ET. Study intervention period will be ≤26 cycles (approximately 2 years) followed by ≤8 years of ET as medically indicated. Participants must have undergone definitive surgery of the primary breast tumor and have high-risk disease. High-risk disease is defined as (i) detection of residual axillary nodal disease at the time of definitive surgery in participants with prior neoadjuvant (neoadj) tx; or (ii) in patients not receiving neoadj tx, must have either ≥4 pathologically positive axillary lymph nodes (pALNs), or 1-3 pathological pALNs and either: histologic Grade 2-3 and/or primary invasive tumor size ≥5 cm. Participants must have received either adjuvant pertuzumab plus trastuzumab with chemotherapy or adjuvant T-DM1. Stratification factors include treatment with neoadj tx, menopausal status, and region. The study is powered at approximately 80% to detect the superiority of abemaciclib plus ET over PB plus ET in terms of IDFS (as defined by the STEEP system) at a 1-sided α =.025 using a log-rank test. Assuming a hazard ratio of 0.73, this requires approximately 324 events at final IDFS analysis. Key secondary objectives include overall survival, distant relapse free survival, safety, pharmacokinetics, and patient-reported outcomes. The study is planned to start in March 2021. Approximately 525 centers in 23 countries plan to enroll ̃2450 participants. Clinical trial information: NCT04752332.

Trial in progress: A phase 3, randomized, double-blind trial of trilaciclib versus placebo in patients receiving first- or second-line gemcitabine and carboplatin for locally advanced unresectable or metastatic triple-negative breast cancer (PRESERVE 2)

TPS1107

Background: Trilaciclib is an intravenous (IV), highly potent and selective, reversible cyclin-dependent kinase (CDK) 4/6 inhibitor that protects hematopoietic stem and progenitor cells during chemotherapy (myeloprotection) and may directly enhance antitumor immunity (anticancer efficacy). In a randomized phase 2 trial of trilaciclib administered prior to gemcitabine and carboplatin (GC) versus GC alone in advanced/metastatic triple-negative breast cancer (mTNBC), although the primary endpoint of myeloprotection was not met, the addition of trilaciclib resulted in a substantial improvement in median overall survival (OS; 19.8 months with trilaciclib vs 12.6 months with placebo, hazard ratio [95% CI] = 0.37 [0.21–0.63]; O’Shaughnessy et al. SABCS 2020 [PD1-06]). Clinically meaningful improvements in OS and progression-free survival (PFS) were also observed in both programmed death ligand-1 (PD-L1)–positive and –negative subsets. Methods: The PRESERVE 2 trial (EudraCT: 2020-004930-39) is a randomized, double-blind, placebo-controlled, international phase 3 trial evaluating the efficacy of trilaciclib administered prior to GC in patients with mTNBC. Two mTNBC patient populations will be studied and analyzed separately: cohort 1 (N = 170) will evaluate first-line, PD-1/PD-L1 inhibitor–naïve patients with ≥6 months between completion of last curative treatment and first recurrence; cohort 2 (N = 80) will evaluate second-line PD-L1–positive patients following ≥4 months of PD-1/PD-L1 inhibitor therapy in the advanced setting. Key eligibility criteria for both cohorts include age ≥18 years, Eastern Cooperative Oncology Group performance status of 0/1, and available tumor tissue. Patients will be randomized (1:1) to trilaciclib 240 mg/m2 or placebo prior to gemcitabine 1000 mg/m2 and carboplatin area under the curve 2 IV on days 1 and 8, every 21 days. Stratification factors (cohort 1 only) include tumor PD-L1 status by Ventana SP-142 IVD assay, disease-free interval, and country. Study treatment will continue until progressive disease per RECIST v1.1, unacceptable toxicity, or investigator/patient decision, after which, patients will be followed every 3 months for survival. Up to 80 patients will be consented for optional paired baseline and on-treatment biopsies. Archival tissue and serial peripheral blood will be collected from all patients. The primary endpoint is OS, and the key secondary endpoint is time to confirmed deterioration in fatigue. Other secondary endpoints include PFS, myeloprotection, and safety/tolerability. Exploratory endpoints will assess pharmacodynamic parameters, including those related to immune-based mechanisms, and efficacy by CDK4/6-dependence signatures. Study enrollment is open. Clinical trial information: 2020-004930-39 .

Stereotactic radiotherapy for oligoprogressive ER-positive breast cancer (AVATAR)

BACKGROUND

The enhanced knowledge of cancer biology has led to considerable advancement in systemic therapy for advanced breast cancer. Recently, studies showed that cyclin-dependent kinase (CDK) 4/6 inhibitor, when added to endocrine therapy, had improved the outcomes of patients with advanced ER-positive HER2-negative breast cancer. However, the disease often progresses following a period of treatment response. In a subset of patients, disease progression may occur at limited sites, i.e., oligoprogressive disease (OPD). In the past few years, stereotactic radiotherapy (SRT) has emerged as a safe and effective treatment for advanced cancer when delivered to limited metastatic sites. Hence, it is worth investigating the role of SRT in the setting of oligoprogressive breast cancer.

METHOD

AVATAR is a multicentre phase II registry trial of SRT with endocrine therapy and CDK 4/6 inhibitor for the management of advanced ER-positive HER2-negative breast cancer. The study aims to enrol 32 patients with OPD limited to 5 lesions. The primary endpoint of the study is time to change systemic therapy measured from the commencement of SRT to change in systemic therapy. Secondary objectives include overall survival, progression free survival and treatment related toxicity. The exploratory objective is to describe the time to change in systemic therapy by the site (bone only vs. non-bone lesions) and number (1 vs. > 1) of OPD.

DISCUSSION

This study aims to explore the effect of SRT in maximising the benefit of systemic therapy in patients with oligoprogressive ER-positive HER2-negative breast cancer. This approach might help reduce the burden of disease and improve the life quality in these patients.

TRIAL REGISTRATION

ACTRN, ACTRN12620001212943 . Date of registration 16 November 2020- Retrospectively registered.

CDK4/6 inhibition reprograms the breast cancer enhancer landscape by stimulating AP-1 transcriptional activity

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) were designed to induce cancer cell cycle arrest. Recent studies have suggested that these agents also exert other effects, influencing cancer cell immunogenicity, apoptotic responses, and differentiation. Using cell-based and mouse models of breast cancer together with clinical specimens, we show that CDK4/6 inhibitors induce remodeling of cancer cell chromatin characterized by widespread enhancer activation, and that this explains many of these effects. The newly activated enhancers include classical super-enhancers that drive luminal differentiation and apoptotic evasion, as well as a set of enhancers overlying endogenous retroviral elements that is enriched for proximity to interferon-driven genes. Mechanistically, CDK4/6 inhibition increases the level of several Activator Protein-1 (AP-1) transcription factor proteins, which are in turn implicated in the activity of many of the new enhancers. Our findings offer insights into CDK4/6 pathway biology and should inform the future development of CDK4/6 inhibitors.

Transforming growth factor β in breast cancer: another new trick for the old dog

Two recent papers from the laboratory of Professor Ming Li demonstrate that inhibition of transforming growth factor β specifically in CD4⁺ T cells can suppress tumor growth through an unanticipated mechanism.

Enhanced toxicity with CDK 4/6 inhibitors and palliative radiotherapy: Non-consecutive case series and review of the literature

5•

CDK 4/6 inhibitors are commonly used in patients with advanced hormone receptor positive breast cancer.

5•

Many patients receive palliative radiotherapy for symptomatic disease concomitantly with a CDK 4/6 inhibitor.

5•

There is a paucity of data on the safety of combining a CDK 4/6 inhibitor with palliative radiotherapy.

5•

We report on 5 cases at our institution where enhanced radiotherapy toxicity was observed when RT was delivered during or prior to treatment with a CDK 4/6 inhibitor.

5•

We review pre-clinical and mechanistic data and hypothesise on possible mechanisms for this phenomenon.

Current first-line systemic treatment in most patients with metastatic hormone receptor-positive, HER-2 negative breast cancer is an aromatase inhibitor in combination with a cyclin dependant kinase (CDK) 4/6 inhibitor. Frequently, these patients require palliative radiotherapy (RT) for symptomatic disease management. There is a paucity of data on the safety of combining a CDK 4/6 inhibitor with palliative RT, with conflicting case reports in the literature. We report on 5 cases at our institution where enhanced radiotherapy toxicity was observed when palliative doses of RT was delivered during or prior to treatment with a CDK 4/6 inhibitor. After review of pre-clinical and mechanistic data, we hypothesise that the effects of CDK4/6 inhibition on normal tissue and the tumour microenvironment may impede tissue recovery and exacerbate acute radiation and radiation recall toxicities. Further studies are required to clarify the potential toxicities of this combination. Clinicians should consider the potential risks when combining CDK 4/6 inhibitors with palliative RT and individualise patient management accordingly.

Pitfalls in assessing stromal tumor infiltrating lymphocytes (sTILs) in breast cancer

Stromal tumor-infiltrating lymphocytes (sTILs) are important prognostic and predictive biomarkers in triple-negative (TNBC) and HER2-positive breast cancer. Incorporating sTILs into clinical practice necessitates reproducible assessment. Previously developed standardized scoring guidelines have been widely embraced by the clinical and research communities. We evaluated sources of variability in sTIL assessment by pathologists in three previous sTIL ring studies. We identify common challenges and evaluate impact of discrepancies on outcome estimates in early TNBC using a newly-developed prognostic tool. Discordant sTIL assessment is driven by heterogeneity in lymphocyte distribution. Additional factors include: technical slide-related issues; scoring outside the tumor boundary; tumors with minimal assessable stroma; including lymphocytes associated with other structures; and including other inflammatory cells. Small variations in sTIL assessment modestly alter risk estimation in early TNBC but have the potential to affect treatment selection if cutpoints are employed. Scoring and averaging multiple areas, as well as use of reference images, improve consistency of sTIL evaluation. Moreover, to assist in avoiding the pitfalls identified in this analysis, we developed an educational resource available at www.tilsinbreastcancer.org/pitfalls.

Report on computational assessment of Tumor Infiltrating Lymphocytes from the International Immuno-Oncology Biomarker Working Group

Assessment of tumor-infiltrating lymphocytes (TILs) is increasingly recognized as an integral part of the prognostic workflow in triple-negative (TNBC) and HER2-positive breast cancer, as well as many other solid tumors. This recognition has come about thanks to standardized visual reporting guidelines, which helped to reduce inter-reader variability. Now, there are ripe opportunities to employ computational methods that extract spatio-morphologic predictive features, enabling computer-aided diagnostics. We detail the benefits of computational TILs assessment, the readiness of TILs scoring for computational assessment, and outline considerations for overcoming key barriers to clinical translation in this arena. Specifically, we discuss: 1. ensuring computational workflows closely capture visual guidelines and standards; 2. challenges and thoughts standards for assessment of algorithms including training, preanalytical, analytical, and clinical validation; 3. perspectives on how to realize the potential of machine learning models and to overcome the perceptual and practical limits of visual scoring.

Ovarian suppression for adjuvant treatment of hormone receptor-positive early breast cancer

BACKGROUND

Approximately 80% of breast cancers amongst premenopausal women are hormone receptor-positive. Adjuvant endocrine therapy is an integral component of care for hormone receptor-positive breast cancer and in premenopausal women includes oestrogen receptor blockade with tamoxifen, temporary suppression of ovarian oestrogen synthesis by luteinising hormone releasing hormone (LHRH) agonists, and permanent interruption of ovarian oestrogen synthesis with oophorectomy or radiotherapy. Recent international consensus statements recommend single-agent tamoxifen or aromatase inhibitors with ovarian function suppression (OFS) as the current standard adjuvant endocrine therapy for premenopausal women (often preceded by chemotherapy). This review examined the role of adding OFS to another treatment (i.e. chemotherapy, endocrine therapy, or both) or comparing OFS to no further adjuvant treatment.

OBJECTIVES

To assess effects of OFS for treatment of premenopausal women with hormone receptor-positive early breast cancer.

SEARCH METHODS

For this review update, we searched the Specialised Register of the Cochrane Breast Cancer Group, MEDLINE, Embase, the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 8), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), and ClinicalTrials.gov on 26 September 2019. We screened the reference lists of related articles, contacted trial authors, and applied no language restrictions.

SELECTION CRITERIA

We included all randomised trials assessing any method of OFS, that is, oophorectomy, radiation-induced ovarian ablation, or LHRH agonists, as adjuvant treatment for premenopausal women with early-stage breast cancer. We included studies that compared (1) OFS versus observation, (2) OFS + chemotherapy versus chemotherapy, (3) OFS + tamoxifen versus tamoxifen, and (4) OFS + chemotherapy + tamoxifen versus chemotherapy + tamoxifen.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed risk of bias and certainty of evidence using the GRADE approach. Hazard ratios (HRs) were derived for time-to-event outcomes, and meta-analysis was performed using a fixed-effect model. The primary outcome measures were overall survival (OS) and disease-free survival (DFS). Toxicity, contralateral breast cancer, and second malignancy were represented as risk ratios (RRs), and quality of life data were extracted when provided.

MAIN RESULTS

This review update included 15 studies involving 11,538 premenopausal women with hormone receptor-positive early breast cancer; these studies were conducted from 1978 to 2014. Some of these treatments are not current standard of care, and early studies did not assess HER2 receptor status. Studies tested OFS versus observation (one study), OFS plus chemotherapy versus chemotherapy (six studies), OFS plus tamoxifen versus tamoxifen (six studies), and OFS plus chemotherapy and tamoxifen versus chemotherapy and tamoxifen (two studies). Of those studies that reported the chemotherapy regimen, an estimated 72% of women received an anthracycline. The results described below relate to the overall comparison of OFS versus no OFS. High-certainty evidence shows that adding OFS to treatment resulted in a reduction in mortality (hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.78 to 0.94; 11 studies; 10,374 women; 1933 reported events). This treatment effect was seen when OFS was added to observation, to tamoxifen, or to chemotherapy and tamoxifen. The effect on mortality was not observed when OFS was added to chemotherapy without tamoxifen therapy (HR 0.95, 95% CI 0.82 to 1.09; 5 studies; 3087 women; median follow-up: range 7.7 to 12.1 years). The addition of OFS resulted in improved DFS (HR 0.83, 95% CI 0.77 to 0.90; 10 studies; 8899 women; 2757 reported events; high-certainty evidence). The DFS treatment effect persisted when OFS was added to observation, to tamoxifen, and to chemotherapy and tamoxifen. The effect on DFS was reduced when OFS was added to chemotherapy without tamoxifen therapy (HR 0.90, 95% CI 0.79 to 1.01; 5 studies; 2450 women). Heterogeneity was low to moderate across studies for DFS and OS (respectively). Evidence suggests that adding OFS slightly increases the incidence of hot flushes (grade 3/4 or any grade; risk ratio (RR) 1.60, 95% CI 1.41 to 1.82; 6 studies; 5581 women; low-certainty evidence, as this may have been under-reported in these studies). Two other studies that could not be included in the meta-analysis reported a higher number of hot flushes in the OFS group than in the no-OFS group. Seven studies involving 5354 women collected information related to mood; however this information was reported as grade 3 or 4 depression, anxiety, or neuropsychiatric symptoms, or symptoms were reported without the grade. Two studies reported an increase in depression, anxiety, and neuropsychiatric symptoms in the OFS group compared to the no-OFS group, and five studies indicated an increase in anxiety in both treatment groups (but no difference between groups) or no difference overall in symptoms over time or between treatment groups. A single study reported bone health as osteoporosis (defined as T score < -2.5); this limited evidence suggests that OFS increases the risk of osteoporosis compared to no-OFS at median follow-up of 5.6 years (RR 1.16, 95% CI 1.10 to 28.82; 2011 women; low-certainty evidence). Adding OFS to treatment likely reduces the risk of contralateral breast cancer (HR 0.75, 95% CI 0.57 to 0.97; 9 studies; 9138 women; moderate-certainty evidence). Quality of life was assessed in five studies; four studies used validated tools, and the fifth study provided no information on how data were collected. Two studies reported worse quality of life indicators (i.e. vaginal dryness, day and night sweats) for women receiving OFS compared to those in the no-OFS group. The other two studies indicated worsening of symptoms (e.g. vasomotor, gynaecological, vaginal dryness, decline in sexual interest, bone and joint pain, weight gain); however these side effects were reported in both OFS and no-OFS groups. The study that did not use a validated quality of life tool described no considerable differences between groups.

AUTHORS' CONCLUSIONS

This review found evidence that supports adding OFS for premenopausal women with early, hormone receptor-positive breast cancers. The benefit of OFS persisted when compared to observation, and when added to endocrine therapy (tamoxifen) or chemotherapy and endocrine therapy (tamoxifen). The decision to use OFS may depend on the overall risk assessment based on tumour and patient characteristics, and may follow consideration of all side effects that occur with the addition of OFS.

Abstract P3-11-10: Health-related quality of life (HRQoL) in monarcHER: Abemaciclib plus trastuzumab with or without fulvestrant versus trastuzumab plus standard-of-care chemotherapy in HR+, HER2+ advanced breast cancer

Background: Abemaciclib is an oral selective inhibitor of cyclin-dependent kinases 4 and 6 approved for hormone receptor (HR)+, human epidermal growth factor receptor 2 (HER2)- metastatic breast cancer. In the randomized, 3-arm, phase 2 study monarcHER (NCT02675231) for HR+, HER2+ advanced breast cancer (ABC), abemaciclib in combination with trastuzumab (T) and fulvestrant (F) significantly improved investigator-assessed progression-free survival (whereas abemaciclib + T did not) versus (vs) T + physician’s choice of chemotherapy and demonstrated a tolerable safety profile. Here, patient-reported HRQoL, functioning, and symptoms are reported.

Methods: In monarcHER, 237 postmenopausal (surgical, natural, or chemical ovarian suppression) women with ABC and ≥2 prior HER2+ directed therapies in the advanced setting were randomized 1:1:1 to abemaciclib (150 mg PO Q12H every 21 days) + T (IV infusion on D1 every 21 days) with F (500 mg IM on Cycle 1 D1 and D15 and Cycle 2 D8, then Q4W; Arm A) or without F (Arm B) vs T + physician’s choice of chemotherapy (per label every 21 days; Arm C). Supportive measures to manage diarrhea were permitted. Patient-reported outcomes were measured at baseline and at each cycle using the modified Brief Pain Inventory-short form (mBPI-sf) and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). The EuroQol 5-Dimension 5 Level (EQ-5D 5L) questionnaire was also collected. Higher scores on EORTC QLQ-C30 functional and health status/QoL scales indicate improvement whereas higher scores on EORTC QLQ-C30 symptom scales and mBPI-sf indicate worsening of symptoms/pain. The EQ-5D 5L index score was calculated from a set of item weights to derive a score of 0-1, with 1 representing the best health status. Treatment arm comparisons of change from baseline (all post-baseline visits) were conducted using a mixed model repeated measure, with .05 considered statistically significant. Clinical meaningfulness was defined as a ≥10-point score change from baseline (on a 0-100 scale) for EORTC QLQ-C30 and a 2-point score change from baseline for mBPI-sf.

Results: Patient-reported outcome compliance rates were ≥90% through Cycle 15; the range for median duration of each treatment component of each arm was 7.5-10.0 cycles. Overall, no statistically significant or clinically meaningful changes from baseline differences were observed between treatment arms for mBPI-sf pain scores or EORTC QLQ-C30 global health score, function scales, or for symptoms of fatigue, dyspnea, appetite loss, or financial difficulties. Least square (LS) mean change from baseline differences showed statistically significant improvements in Arm A vs C for EORTC QLQ-C30 symptoms of pain (-6.81; p=.026) and insomnia (-6.39; p=.041). Worsening for the symptom of nausea/vomiting was statistically significant but not clinically meaningful in Arm A vs C (4.08; p=.043). Diarrhea showed a statistically significant and clinically meaningful worsening in Arm A vs C (19.27; p&lt;.001). A by-cycle analysis showed mean nausea/vomiting and diarrhea symptom scores were generally higher during earlier visits and returned to near-baseline levels after treatment discontinuation. The EQ-5D 5L index score improved in Arm A vs C, with an LS mean change from baseline difference of .05 (p=.033).

Conclusions: Quality of life was maintained for patient-reported pain, global health, functioning, and most symptoms when abemaciclib was added to T + F compared with physician’s choice of chemotherapy in patients with HR+, HER2+ ABC. Gastrointestinal-related symptoms were transient and consistent with the manageable, reversible adverse event profile.

Citation Format: Sara M Tolaney, Andrew M Wardley, Stefania Zambelli, John F. Hilton, Tiffany A Troso-Sandoval, Francesco Ricci, Seock-Ah Im, Sung-Bae Kim, Stephen RD Johnston, Arlene Chan, Shom Goel, Kristen Catron, Zhengyu Yang, M. Corona Gianford, Gregory L Price, Fabrice André. Health-related quality of life (HRQoL) in monarcHER: Abemaciclib plus trastuzumab with or without fulvestrant versus trastuzumab plus standard-of-care chemotherapy in HR+, HER2+ advanced breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-11-10.

Abstract P4-06-01: Using multi-omic profiling to unravel the complexity of triple-negative breast cancer (TNBC)

Introduction: TNBCs show marked heterogeneity in their spectrum of genomic alterations, patterns of gene expression, proteomic profiles, and immune microenvironments. Although TNBC heterogeneity has been characterized at each of these levels individually, how variation at one level is associated with differences at other levels is poorly understood. As new targeted and immune-based therapies are developed for TNBC, there is a critical need to better understand this interplay. In this study, we performed “multi-omic” profiling on a cohort of TNBCs in order to determine how various DNA, RNA, protein, and immunologic parameters are correlated.

Methods: A cohort of 95 formalin-fixed, paraffin-embedded tumor specimens from primary and metastatic TNBCs was curated. The following parameters in each tumor specimen were quantified: stromal tumor-infiltrating lymphocytes (sTILs) assessed on hematoxylin and eosin stained sections; expression of programmed death-ligand 1 (PD-L1), androgen receptor (AR) and the retinoblastoma tumor suppressor protein (RB) by immunohistochemistry (IHC); and expression of 776 breast cancer-related transcripts (using the nCounter Breast Cancer 360 panel). Targeted tumor DNA sequencing was performed in a subset of cases and tumor mutational burden (TMB) and DNA mismatch repair (MMR) status were determined. Gene expression patterns were analyzed using customized algorithms and we performed descriptive statistics to evaluate associations between DNA, RNA, and protein variables.

Results: All 95 TNBC specimens were analyzed for sTILs; IHC for RB, AR, and PD-L1; and transcriptomic profiling. DNA sequencing was performed on 68 cases. The genomic, transcriptomic, and proteomic classification of the cohort is provided in Table 1.

AR+ TNBCs (&gt;1% tumor cells on IHC) were more likely to be non-basal (p&lt;0.001), showed higher levels of AR (p&lt;0.001) and FOXA1 (p&lt;0.01) transcripts, were enriched for expression of genes related to mammary differentiation (p&lt;0.001), depleted for expression of genes related to proliferation (p=0.018), “BRCAness” (p&lt;0.001), and homologous recombination deficiency (HRD) (p=0.045), and showed significant upregulation of the immune inhibitory checkpoint molecule TIGIT (p=0.004).

RB-positivity (&gt;50% tumor cells on IHC) correlated with higher RB1 transcript levels but not with RB1 deletion/mutation status. RB+ tumors were depleted for expression of genes associated with HRD and BRCAness (p=0.029 and p=0.071).

TNBCs showing widespread upregulation of gene expression signatures related to numerous immune processes included those with: (i) higher levels of sTILs, (ii) &gt;1% PD-L1+ stromal mononuclear cells and/or tumor cells, (iii) tumors without RB1 or TP53 alterations. Genomic aberration in the PI3K pathway was associated with increased expression of AR and FOXA1 but not with alterations in immune gene expression.

Conclusion: Patterns exist connecting TNBC heterogeneity across the DNA, RNA, and protein levels. Further analyses determining associations between genomic, transcriptomic, and proteomic features in this cohort of TNBC will be presented at the meeting.

Genomic, transcriptomic, and proteomic classification of tumors in the entire TNBC cohortTumor site (n=95)Primary64 (67%)Regional nodal4 (4%)Distant nodal or visceral27 (28%)Stromal TILs (n=93)&lt;10%50 (53%)10-49%30 (32%)&gt;50%13 (14%)RB staining (n=95)Positive (&gt;50% tumor cells)52 (55%)AR staining (n=95)Positive (&gt;1% tumor cells)34 (36%)PD-L1 staining (stromal, n=94)Positive (&gt;1% mononuclear cells)34 (37%)PD-L1 staining (tumor, n=94)&gt;1% tumor cells27 (29%)PAM50 subtype (n=90)Basal72 (80%)HER2-enriched15 (17%)Luminal B3 (3%)TNBC subtype (n=91)Basal-like immune activated (BLIA)76 (80%)Basal-like immunosuppressed (BLIS)7 (7%)Mesenchymal (MES)8 (8%)Luminal androgen receptor (LAR)4 (4%)DNA alterations (n=68)TP53 alterations54 (80%)BRCA1/2 mutations14 (21%)RB1 alterations21 (31%)PI3K pathway alterations31 (46%)

Citation Format: Shom Goel, Heather Ann Brauer, Yuqi Ren, Kara Gorman, Wafa Osmani, Jessica Pittenger, Chelsea Andrews, Edward T Richardson III, Elizabeth A Mittendorf, MD PhD, Eric P Winer, Stuart Schnitt, Sara M Tolaney. Using multi-omic profiling to unravel the complexity of triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-06-01.