Pembrolizumab monotherapy for previously untreated, PD-L1-positive, metastatic triple-negative breast cancer: cohort B of the phase II KEYNOTE-086 study

PD-1/PD-L1 axis importance and tumor microenvironment immune cells

Triple-negative breast cancer (TNBC) is heterogeneous cancer with poor prognosis among the other breast tumors. Rapid recurrence and increased progression rate could be reasons for the poor prognosis of this type of breast cancer. Recently, because of the lack of specific targets in multiple cancer treatment, immune checkpoint blockade therapies with targeting PD-1/PD-L1 axis have displayed significant advances and improved survival. Among different types of breast cancers, TNBC is considered more immunogenic with high T-cell and other immune cells infiltration compared to other breast cancer subtypes. This immunogenic characteristic of TNBC is a beneficial marker in the immunotherapy of these tumors. Clinical studies with a focus on immune checkpoint therapy have demonstrated promising results in TNBC treatment. In this review, we summarize clinical trials with the immunotherapy-based treatment of different cancers and also discuss the interaction between infiltrating immune cells and breast tumor microenvironment. In addition, we focus on the signaling pathway that controls PD-L1 expression and continues with CAR T-cell therapy and siRNA as novel strategies and potential tools in targeted therapy.

Current advances in the diagnosis and personalized treatment of breast cancer: lessons from tumor biology

Breast cancer treatment has advanced enormously in the last decade. Most of this is due to advances reached in the knowledge regarding tumor biology, mainly in the field of diagnosis and treatment. This review brings information about how the genomics-based information contributed to advances in breast cancer diagnosis and prognosis perspective, as well as presents how tumor biology discoveries fostered the main therapeutic approaches available to treat such patients, based on a personalized point of view.

Efficacy and predictive factors of immune checkpoint inhibitors in metastatic breast cancer: a systematic review and meta-analysis

BACKGROUND

Immune checkpoint inhibitors (ICIs) have shown encouraging treatment efficacy for metastatic breast cancer in several clinical trials. However, response only occurred in a small population. Evidence predicting response and survival of patients with metastatic breast cancer following ICI treatment with existing biomarkers has not been well summarized. This review aimed to summarize the efficacy and predictive factors of immune checkpoint therapy in metastatic breast cancer, which is critical for clinical practice.

METHODS

PubMed, Embase, Cochrane Library, Web of Science, www.clinicaltrials.gov, and meeting abstracts were comprehensively searched to identify clinical trials. The outcomes were objective response rate (ORR), treatment-related adverse events (trAEs), immune-related adverse events (irAEs), progression-free survival (PFS), and overall survival (OS).

RESULTS

In this review, 27 studies with 1746 patients were included for quantitative synthesis. The pooled ORR was 19% [95% confidence interval (CI) = 12-27%]. Programmed death-ligand 1 (PD-L1)-positive patients had a higher response rate [odds ratio (OR) = 1.44, p = 0.01]. First-line immunotherapy had a better ORR than second-line immunotherapy (OR = 2.00, p = 0.02). Tumor-infiltrating lymphocytes (TILs) ⩾5% (OR = 2.53, p = 0.002) and high infiltrated CD8+ T-cell level (OR = 4.33, p = 0.006) were ideal predictors of immune checkpoint therapy response. Liver metastasis indicated poor response (OR = 0.19, p = 0.009). However, the difference was non-significant in ORR based on age, performance status score, lymph node metastasis, and lactate dehydrogenase (LDH) level. In addition, the PD-L1-positive subgroup had a better 1-year PFS (OR = 1.55, p = 0.04) and 2-year OS (OR = 2.28, p = 0.02) following ICI treatment. The pooled incidence during ICI therapy of grade 3-4 trAEs was 25% (95% CI = 16-34%), whereas for grade 3-4 irAEs it was 15% (95% CI = 11-19%).

CONCLUSIONS

Metastatic breast cancer had modest response to ICI therapy. PD-L1-positive, first-line immunotherapy, non-liver metastasis, and high TIL and CD8+ T-cell infiltrating levels could predict better response to ICI treatment. Patients with PD-L1-positive tumor could gain more survival benefits from immune checkpoint therapy.

Progress in systemic therapy for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with a heterogeneous genetic profile. Chemotherapy exhibits substantial activity in a small subset of these patients. Drug resistance is inevitable. Major progress has been made in the genetic analysis of TNBC to identify novel targets and increase the precision of therapeutic intervention. Such progress has translated into major advances in treatment strategies, including modified chemotherapy approaches, immune checkpoint inhibitors, and targeted therapeutic drugs. All of these strategies have been evaluated in clinical trials. Nevertheless, patient selection remains a considerable challenge in clinical practice.

Triple-negative breast cancer: new treatment strategies in the era of precision medicine

Triple-negative breast cancer (TNBC) remains the most aggressive cluster of all breast cancers, which is due to its rapid progression, high probabilities of early recurrence, and distant metastasis resistant to standard treatment. Following the advances in cancer genomics and transcriptomics that can illustrate the comprehensive profiling of this heterogeneous disease, it is now possible to identify different subclasses of TNBC according to both intrinsic signals and extrinsic microenvironment, which have a huge influence on predicting response to established therapies and picking up novel therapeutic targets for each cluster. In this review, we summarize basic characteristics and critical subtyping systems of TNBC, and particularly discuss newly found prospective targets and relevant medications, which were proved promising in clinical trials, thus shedding light on the future development of precision treatment strategies.

Different patterns of treatment-related adverse events of programmed cell death-1 and its ligand-1 inhibitors in different cancer types: A meta-analysis and systemic review of clinical trials

Programmed cell death receptor-1 and its ligand-1 (PD-1/PD-L1) inhibitors have been applied to many cancers, but the difference of treatment-related adverse events (AEs) across cancer types remains unknown. We performed a meta-analysis and systemic review to compare the incidences of commonly reported all-grade AEs across cancer types and found that the most frequent AEs were fatigue, rash/pruritus, loss of appetite/nausea and diarrhea. However, each cancer type also had its higher incidences of AEs involving a relevant system, such as melanoma with epidermal AEs (rash, diarrhea and enterocolitis), lung cancer with dyspnea and pneumonitis, digestive system cancers with amylase and lipase elevation; and renal cell and urothelial cancer with kidney injury (creatinine elevation and proteinuria). However, the incidence of hepatitis did not follow the pattern to show a difference. We did another comparison between PD-1 and PD-L1 inhibitors in lung cancer and urothelial cancer respectively, and found that the risk of most AEs did not differ much, except for more hypothyroidism in PD-1 inhibitors, and more kidney injury in PD-L1 inhibitors. Besides possible immunological mechanisms for treatment-related AEs, the influence of previous radiotherapy and the clinical characteristics of the diseases themselves should also be considered and is worth further investigation. With the result of this meta-analysis, clinicians could estimate the risk of certain AE in certain cancer type, to make treatment options and to customize monitor strategies.

Current and emerging biologic therapies for triple negative breast cancer

INTRODUCTION

Triple negative breast cancer, defined by a lack of estrogen receptor, progesterone receptor, or human epidermal growth factor2, accounts for approximately 15% of breast cancer patients. Treatment options have historically been limited to chemotherapy, which has significant toxicity and a suboptimal impact on the five-year relapse rate and survival.

AREAS COVERED

Transcriptomic analyses reveal that TNBC is biologically heterogenous. Predictive biomarkers based on the distinct biology of the different subtypes of TNBC should identify patients that will derive the greatest benefit from a specifically targeted therapeutic agent. Two biomarker-driven treatments have recently been approved: poly-ADP ribose polymerase inhibitors for patients with germline BRCA mutations and atezolizumab in combination with nab-paclitaxel for patients expressing PD-L1 on tumor-infiltrating immune cells.

EXPERT OPINION

Identifying informative predictive biomarkers is critical for the optimal development of targeted drugs for TNBC. Some targeted agents, such as the antibody-drug conjugate sacituzumab govitecan-hziy and the precision medicines capivasertib and ipatisertib, have already shown promising results in early clinical trials, and the results of definitive phase 3 trials are eagerly awaited. Additionally, testing novel immunotherapies and other targeted agents in earlier stages of disease, particularly the neoadjuvant setting, is a high priority.

Immune system and angiogenesis-related potential surrogate biomarkers of response to everolimus-based treatment in hormone receptor-positive breast cancer: an exploratory study

Purpose

mTOR inhibitor everolimus is used for hormone receptor-positive (HR+)/HER2-negative metastatic breast cancer (mBC). No reliable predictive biomarker of response is available. Following evidences from other solid tumors, we aimed to assess the association between treatment-associated immune system features and everolimus activity.

Methods

We retrospectively explored a correlation with the therapeutic activity of everolimus and tumor-associated immune pathways with ingenuity pathway analysis (IPA), neutrophil-to-lymphocyte ratio (NLR), circulating lymphocytes, and endothelial cells (CECs) in 3 different HR+ mBC studies, including the BALLET phase IIIb study.

Results

The circulating levels of CD3⁺/CD8⁺, CD3⁺/CD4⁺, and overall T lymphocytes were higher in responders versus non-responders at baseline (p = 0.017, p < 0.001, p = 0.034) and after treatment (p = 0.01, p = 0.003, p = 0.023). Reduced CECs, a tumor neoangiogenesis marker, were observed in responders after treatment (p < 0.001). Patients with low NLR (≤ 4.4) showed a better progression-free survival compared to patients with high NLR (> 4.4) (p = 0.01). IPA showed that the majority of immunity-related genes were found upregulated in responders compared to non-responders before treatment, but not after.

Conclusions

Lymphocytes subpopulations, CECs and NLR could be interesting biomarkers predictive of response to everolimus-based regimens, potentially useful in daily clinical practice to select/monitor everolimus-based treatment in mBC. Further studies to confirm such hypotheses are warranted.

Identification of Cardiac Glycosides as Novel Inhibitors of eIF4A1-Mediated Translation in Triple-Negative Breast Cancer Cells

The eukaryotic translation initiation factor 4F complex (eIF4F) is a potential chemotherapeutic target in triple-negative breast cancer (TNBC). This complex regulates cap-dependent translational initiation and consists of three core proteins: eIF4E, eIF4G, and eIF4A1. In this study, we focus on repositioning compounds as novel inhibitors of eIF4A1-mediated translation. In order to accomplish this goal, a modified synthetic reporter assay was established. More specifically, a (CGG)₄ motif, which confers eIF4A dependency, was incorporated into the 5'-leader region of a luciferase-tdTomato lentiviral reporter construct. The Prestwick Chemical Library was then screened in multiple TNBC cell lines by measuring the tdTomato fluorescent intensity. We identified several cardiac glycosides as potential inhibitors of eIF4A1-mediated translation. Based on our studies, we find that cardiac glycosides inhibit the expression of eIF4A1. To identify a potential mechanism by which this was occurring, we utilized the Integrative Library of Integrated Network-Based Cellular Signatures (iLINCS). Our pursuits led us to the discovery that cardiac glycosides also decrease levels of c-MYC. Quantitative PCR confirmed that decreases in c-MYC and eIF4A were occurring at the transcriptional level. As such, disruption of the eIF4A1-c-MYC axis may be a viable approach in the treatment of TNBC. The novel combination of rocaglamide A and digoxin exhibited synergistic anti-cancer activity against TNBC cells in vitro. The findings in this study and others are important for formulating potential combination chemotherapies against eIF4A1 in vivo. Thus, drug repositioning may be one classical approach to successfully target eIF4A1 in TNBC patients.

Polyamine Blocking Therapy Decreases Survival of Tumor-Infiltrating Immunosuppressive Myeloid Cells and Enhances the Antitumor Efficacy of PD-1 Blockade

Despite unprecedented advances in the treatment of cancer through the use of immune checkpoint blockade (ICB), responses are not universal and alternative strategies are needed to enhance responses to ICB. We have shown previously that a novel polyamine blocking therapy (PBT), consisting of cotreatment with α-difluoromethylornithine (DFMO) to block polyamine biosynthesis and a Trimer polyamine transport inhibitor, decreases myeloid-derived suppressor cells (MDSC) and M2-like tumor-associated macrophages (TAM). Both MDSCs and TAMs promote tumor progression, inhibit antitumor immunity, and limit the efficacy of ICB. In this study, we investigated the use of PBT to heighten therapeutic responses to PD-1 blockade in mice bearing 4T1 mammary carcinoma and B16F10 melanoma tumors. Whereas PBT inhibited primary tumor growth in both tumor models, 4T1 lung metastases were also dramatically decreased in mice treated with PBT. Reductions in MDSC and TAM subpopulations in 4T1 tumors from PBT-treated mice were accompanied by reduced cytoprotective autophagy only in tumor-infiltrating MDSC and macrophage subpopulations but not in the lung or spleen. PBT treatment blunted M2-like alternative activation of bone marrow-derived macrophages and reduced STAT3 activation in MDSC cultures while increasing the differentiation of CD80⁺, CD11c⁺ macrophages. PBT significantly enhanced the antitumor efficacy of PD-1 blockade in both 4T1 and B16F10 tumors resistant to anti-PD-1 monotherapy, increasing tumor-specific cytotoxic T cells and survival of tumor-bearing animals beyond that with PBT or PD-1 blockade alone. Our results suggest that cotreatment with DFMO and the Trimer polyamine transport inhibitor may improve the therapeutic efficacy of immunotherapies in patients with cancer with resistant tumors.

Comprehensive analysis and establishment of a prediction model of alternative splicing events reveal the prognostic predictor and immune microenvironment signatures in triple negative breast cancer

Background

Triple-negative breast cancer (TNBC) is widely concerning because of high malignancy and poor prognosis. There is increasing evidence that alternative splicing (AS) plays an important role in the development of cancer and the formation of the tumour microenvironment. However, comprehensive analysis of AS signalling in TNBC is still lacking and urgently needed.

Methods

Transcriptome and clinical data of 169 TNBC tissues and 15 normal tissues were obtained and integrated from the cancer genome atlas (TCGA), and an overview of AS events was downloaded from the SpliceSeq database. Then, differential comparative analysis was performed to obtain cancer-associated AS events (CAAS). Metascape was used to perform parent gene enrichment analysis based on CAAS. Unsupervised cluster analysis was performed to analyse the characteristics of immune infiltration in the microenvironment. A splicing network was established based on the correlation between CAAS events and splicing factors (SFs). We then constructed prediction models and assessed the accuracy of these models by receiver operating characteristic (ROC) curve and Kaplan–Meier survival analyses. Furthermore, a nomogram was adopted to predict the individualized survival rate of TNBC patients.

Results

We identified 1194 cancer-associated AS events (CAAS) and evaluated the enrichment of 981 parent genes. The top 20 parent genes with significant differences were mostly related to cell adhesion, cell component connection and other pathways. Furthermore, immune-related pathways were also enriched. Unsupervised clustering analysis revealed the heterogeneity of the immune microenvironment in TNBC. The splicing network also suggested an obvious correlation between SFs expression and CAAS events in TNBC patients. Univariate and multivariate Cox regression analyses showed that the survival-related AS events were detected, including some significant participants in the carcinogenic process. A nomogram incorporating risk, AJCC and radiotherapy showed good calibration and moderate discrimination.

Conclusion

Our study revealed AS events related to tumorigenesis and the immune microenvironment, elaborated the potential correlation between SFs and CAAS, established a prognostic model based on survival-related AS events, and created a nomogram to better predict the individual survival rate of TNBC patients, which improved our understanding of the relationship between AS events and TNBC.

Molecular subtyping and genomic profiling expand precision medicine in refractory metastatic triple-negative breast cancer: the FUTURE trial

Triple-negative breast cancer (TNBC) is a highly heterogeneous disease, and molecular subtyping may result in improved diagnostic precision and targeted therapies. Our previous study classified TNBCs into four subtypes with putative therapeutic targets. Here, we conducted the FUTURE trial (ClinicalTrials.gov identifier: NCT03805399), a phase Ib/II subtyping-based and genomic biomarker-guided umbrella trial, to evaluate the efficacy of these targets. Patients with refractory metastatic TNBC were enrolled and stratified by TNBC subtypes and genomic biomarkers, and assigned to one of these seven arms: (A) pyrotinib with capecitabine, (B) androgen receptor inhibitor with CDK4/6 inhibitor, (C) anti PD-1 with nab-paclitaxel, (D) PARP inhibitor included, (E) and (F) anti-VEGFR included, or (G) mTOR inhibitor with nab-paclitaxel. The primary end point was the objective response rate (ORR). We enrolled 69 refractory metastatic TNBC patients with a median of three previous lines of therapy (range, 1–8). Objective response was achieved in 20 (29.0%, 95% confidence interval (CI): 18.7%–41.2%) of the 69 intention-to-treat (ITT) patients. Our results showed that immunotherapy (arm C), in particular, achieved the highest ORR (52.6%, 95% CI: 28.9%–75.6%) in the ITT population. Arm E demonstrated favorable ORR (26.1%, 95% CI: 10.2%–48.4% in the ITT population) but with more high grade (≥ 3) adverse events. Somatic mutations of TOP2A and CD8 immunohistochemical score may have the potential to predict immunotherapy response in the immunomodulatory subtype of TNBC. In conclusion, the phase Ib/II FUTURE trial suggested a new concept for TNBC treatment, demonstrating the clinical benefit of subtyping-based targeted therapy for refractory metastatic TNBC.

Evaluation of PD-L1, tumor-infiltrating lymphocytes, and CD8+ and FOXP3+ immune cells in HER2-positive breast cancer treated with neoadjuvant therapies

BACKGROUND

The tumor immune microenvironment plays a critical role in the prognosis and outcome of breast cancers. This study examined the role of tumor-infiltrating lymphocytes (TILs), CD8+, FOXP3+ lymphocytes, PD-L1 expression, and other clinicopathological parameters in HER2+ breast cancer and correlate with tumor response to neoadjuvant therapy.

METHODS

We included 173 HER2+ patients treated with neoadjuvant HER2-targeted chemotherapy regimens from 2010 to 2016. 67 cases had biopsy blocks to evaluate TIL, CD8, FOXP3, and PD-L1 immunohistochemistry staining. Tumors were classified as pCR vs non-pCR group. Clinicopathological parameters, TIL, CD8+ and FOXP3+ cell count, and PD-L1 expression were correlated with pCR rate.

RESULTS

Univariate analyses showed that pCR rate was significantly correlated with low PR, low ER, high Ki-67, high FOXP3, HER2 IHC3+ , high HER2 ratio and copy number. By multivariate analysis, Ki-67 was the only variable significantly correlated with pCR. PD-L1 expression was detected in 9.2% cases. TIL hotspot has a non-significant correlation with pCR rate (p = 0.096).

CONCLUSIONS

High Ki-67 is a strong predictor for pCR in HER2+ breast cancer. TIL and FOXP3 T cells may play a role in tumor response in HER2+ cancer. PD-L1 is expressed in a subset of HER2+ breast cancer, supporting a role of immunotherapy in treating a subset of HER2+ breast cancers. The role of PD-L1, TIL, and other markers of immunogenicity as predictors of response to neoadjuvant chemotherapy in HER2+ breast cancer should be further evaluated.

Tumoral PD-1hiCD8+ T cells are partially exhausted and predict favorable outcome in triple-negative breast cancer

Tumor-infiltrating PD-1hi dysfunctional CD8+ T cells have been identified in several tumors but largely unexplored in breast cancer (BC). Here we aimed to extensively explore PD-1hiCD8+ T cells in BC, focusing on the triple-negative BC (TNBC) subtype. Flow cytometry was used to study the phenotypes and functions of CD8+ T-cell subsets in peripheral blood and surgical specimens from treatment-naive BC patients. RNA-seq expression data generated to dissect the molecular features of tumoral PD-1neg, PD-1lo and PD-1hi CD8+ T cells. Further, the associations between tumoral PD-1hi CD8+ T cells and the clinicopathological features of 503 BC patients were explored. Finally, multiplexed immunohistochemistry (mIHC) was performed to evaluate in situ PD-1hiCD8+ T cells on the tissue microarrays (TMAs, n=328) for prognostic assessment and stratification of TNBC patients. PD-1hiCD8+ T cells found readily detectable in tumor tissues but rarely in peripheral blood. These cells shared the phenotypic and molecular features with exhausted and tissue-resident memory T cells (TRM) with a skewed TCR repertoire involvement. Interestingly, PD-1hiCD8+ T cells are in the state of exhaustion characterized by higher T-BET and reduced EOMES expression. PD-1hiCD8+ T cells found preferentially enriched within solid tumors, but predominant stromal infiltration of PD-1hiCD8+ T subset was associated with improved survival in TNBC patients. Taken together, tumoral PD-1hiCD8+ T-cell subpopulation in BC is partially exhausted, and their abundance signifies 'hot' immune status with favorable outcomes. Reinvigorating this population may provide further therapeutic opportunities in TNBC patients.

Exhausted T cell signature predicts immunotherapy response in ER-positive breast cancer

Responses to immunotherapy are uncommon in estrogen receptor (ER)-positive breast cancer and to date, lack predictive markers. This randomized phase II study defines safety and response rate of epigenetic priming in ER-positive breast cancer patients treated with checkpoint inhibitors as primary endpoints. Secondary and exploratory endpoints included PD-L1 modulation and T-cell immune-signatures. 34 patients received vorinostat, tamoxifen and pembrolizumab with no excessive toxicity after progression on a median of five prior metastatic regimens. Objective response was 4% and clinical benefit rate (CR + PR + SD > 6 m) was 19%. T-cell exhaustion (CD8⁺ PD-1⁺/CTLA-4⁺) and treatment-induced depletion of regulatory T-cells (CD4⁺ Foxp3⁺/CTLA-4⁺) was seen in tumor or blood in 5/5 patients with clinical benefit, but only in one non-responder. Tumor lymphocyte infiltration was 0.17%. Only two non-responders had PD-L1 expression >1%. This data defines a novel immune signature in PD-L1-negative ER-positive breast cancer patients who are more likely to benefit from immune-checkpoint and histone deacetylase inhibition (NCT02395627).

Efficacy of PD-1/PD-L1 blockade monotherapy in clinical trials

Background:

Inhibitors targeting programmed cell death 1 (PD-1) and programmed death-ligand 1 (PD-L1) have unprecedented effects in cancer treatment. However, the objective response rates (ORRs), progression-free survival (PFS), and overall survival (OS) of PD-1/PD-L1 blockade monotherapy have not been systematically evaluated.

Methods:

We searched Embase, PubMed, and Cochrane database from inception to July 2019 for prospective clinical trials on single-agent PD-1/PD-L1 antibodies (avelumab, atezolizumab, durvalumab, cemiplimab, pembrolizumab, and nivolumab) with information regarding ORR, PFS, and OS.

Results:

Totally, 28,304 patients from 160 perspective trials were included. Overall, 4747 responses occurred in 22,165 patients treated with PD-1/PD-L1 monotherapy [ORR, 20.21%; 95% confidence interval (CI), 18.34–22.15%]. Compared with conventional therapy, PD-1/PD-L1 blockade immunotherapy was associated with more tumor responses (odds ratio, 1.98; 95% CI, 1.52–2.57) and better OS [hazard ratio (HR), 0.75; 95% CI, 0.67–0.83]. The ORRs varied significantly across cancer types and PD-L1 expression status. Line of treatment, clinical phase and drug target also impacted the response rates in some tumors. A total of 2313 of 9494 PD-L1 positive patients (ORR, 24.39%; 95% CI, 22.29–26.54%) and 456 of 4215 PD-L1 negative patients (ORR, 10.34%; 95% CI, 8.67–12.14%) achieved responses. For PD-L1 negative patients, the ORR (odds ratio, 0.92; 95% CI, 0.70–1.20) and PFS (HR, 1.15; 95% CI, 0.87–1.51) associated with immunotherapy and conventional treatment were similar. However, PD-1/PD-L1 blockade monotherapy decreased the risk of death in both PD-L1 positive (HR, 0.66; 95% CI, 0.60–0.72) and PD-L1 negative (HR, 0.86; 95% CI, 0.74–0.99) patients compared with conventional therapy.

Conclusion:

The efficacies associated with PD-1/PD-L1 monotherapy vary significantly across cancer types and PD-L1 expression. This comprehensive summary of clinical benefit from immunotherapy in cancer patients provides an important guide for clinicians.

Neo-adjuvant therapy for triple-negative breast cancer: Insights from a network meta-analysis

BACKGROUND

The best regimen of neo-adjuvant therapy for triple-negative breast cancer (TNBC) is unknown. Recent studies have shown promising data that adding carboplatin or pembrolizumab improves the rate of pathologic complete response (pCR) in TNBC. Therefore, we performed a network meta-analysis to define the overall, most effective, neo-adjuvant systemic therapy for TNBC.

METHODS

We searched for studies comparing different neo-adjuvant regimens in patients with TNBC. We performed a network meta-analysis comparing the regimens using the random-effects model. We focused on anthracycline, bevacizumab, pembrolizumab, and platinum salts (Pl). All study regimens contained a taxane. We analyzed the rate of pCR (ypT0/is, N0), and the incidence of febrile neutropenia, grade 3-grade 4 thrombocytopenia, nausea/vomiting, and diarrhea.

RESULTS

We identified a total of 13 randomized control trials for this analysis. We compared ten different classes of regimens. We found that regimens containing Pl were significantly superior to non-PI-containing regimens for the rate of pCR. Similarly, pembrolizumab-containing regimens were associated with significantly higher pCR rates. Regimens containing bevacizumab significantly increased the rate of pCR as well. However, it was equivocal as to whether the addition of Pl to pembrolizumab-containing regimen increases pCR rates. Adding anthracycline into the regimen did not show an improved rate of pCR. In the safety analysis, regimens containing Pl were associated with a significantly higher incidence of febrile neutropenia and grade 3-grade 4 thrombocytopenia. The regimen containing anthracycline plus bevacizumab plus Pl was associated with a higher risk of gastrointestinal adverse events.

CONCLUSIONS

For TNBC, regimens containing bevacizumab, pembrolizumab, or Pl are most effective in terms of pCR rates, though it is unclear whether combining all these medications has the greatest efficacy. Additionally, the benefit of using anthracycline in the neo-adjuvant therapy regimen for TNBC is not apparent, which may warrant a further head-to-head comparison.

Meta-analysis of immune-related adverse events of immune checkpoint inhibitor therapy in cancer patients

BACKGROUND

Immune checkpoint inhibitors (ICIs) have significant clinical efficacy in the treatment of non-small cell lung cancer (NSCLC); however, the incidence of immune-related adverse events (irAEs) of up to 50% has prevented their widespread use. With the increase in the use of ICIs alone or as combination therapy, clinicians are required to have a better understanding of irAEs and be able to manage them systematically. In this study, we aimed to assess the incidence of irAEs associated with ICIs.

METHODS

We searched PubMed, Embase, and the Web of Science databases, and also included relevant literature references to widen our search. The relevant data with inclusion criteria were performed using RevMan 3.6.0 for meta-analysis. We undertook a systematic literature search which included published data up to December 2019.

RESULTS

Overall, 147 articles and 23 761 cancer patients with 11 different ICI treatment-related (grade 1-5 and 3-5) irAEs were included in the study. There were 46 articles on pembrolizumab (6598 patients), 27 on nivolumab (3576 patients), 13 on atezolizumab (2787 patients), 12 on avelumab (3213 patients), 10 on durvalumab (1780 patients), 22 on ipilimumab (4067 patients), eight on tremelimumab (1158 patients), three on JS001 (223 patients), four on camrelizumab (SHR-1210) (178 patients), one on sintilimab (96 patients), and one on cemiplimab (85 patients). Grade 1-5 irAEs were: cytotoxic T lymphocyte antigen 4 (CTLA-4) (82.87%), programmed cell death 1 (PD-1) (71.89%), and programmed cell death ligand-1 (PD-L1) (58.95%). Subgroup analysis was: Avelumab (44.53%), durvalumab (66.63%), pembrolizumab (67.25%), atezolizumab (68.77%), nivolumab (76.25%), Ipilimumab (82.18%), and tremelimumab (86.78%). Grade 3-5 irAEs were: CTLA-4 (27.22%), PD-1(17.29%), and PD-L1(17.29%). Subgroup analysis was: Avelumab (5.86%), durvalumab (13.43%), atezolizumab (14.45%), nivolumab (15.72%), pembrolizumab (16.58%), tremelimumab (22.04%), and ipilimumab (28.27%).

CONCLUSIONS

This meta-analysis confirmed that anti-PD-1 and anti-PD-L1 inhibitors had a lower incidence of irAEs compared with anti-CTLA-4 inhibitors.

Biomarkers in Triple-Negative Breast Cancer: State-of-the-Art and Future Perspectives

Triple-negative breast cancer (TNBC) is a heterogeneous group of tumors characterized by aggressive behavior, high risk of distant recurrence, and poor survival. Chemotherapy is still the main therapeutic approach for this subgroup of patients, therefore, progress in the treatment of TNBC remains an important challenge. Data derived from molecular technologies have identified TNBCs with different gene expression and mutation profiles that may help developing targeted therapies. So far, however, only a few of these have shown to improve the prognosis and outcomes of TNBC patients. Robust predictive biomarkers to accelerate clinical progress are needed. Herein, we review prognostic and predictive biomarkers in TNBC, discuss the current evidence supporting their use, and look at the future of this research field.

Comparison of three scoring methods using the FDA-approved 22C3 immunohistochemistry assay to evaluate PD-L1 expression in breast cancer and their association with clinicopathologic factors

BACKGROUND

In the evaluation of PD-L1 expression to select patients for anti-PD-1/PD-L1 treatment, uniform guidelines that account for different immunohistochemistry assays, different cell types and different cutoff values across tumor types are lacking. Data on how different scoring methods compare in breast cancer are scant.

METHODS

Using FDA-approved 22C3 diagnostic immunohistochemistry assay, we retrospectively evaluated PD-L1 expression in 496 primary invasive breast tumors that were not exposed to anti-PD-1/PD-L1 treatment and compared three scoring methods (TC: invasive tumor cells; IC: tumor-infiltrating immune cells; TCIC: a combination of tumor cells and immune cells) in expression frequency and association with clinicopathologic factors.

RESULTS

In the entire cohort, positive PD-L1 expression was observed in 20% of patients by TCIC, 16% by IC, and 10% by TC, with a concordance of 87% between the three methods. In the triple-negative breast cancer patients, positive PD-L1 expression was observed in 35% by TCIC, 31% by IC, and 16% by TC, with a concordance of 76%. Associations between PD-L1 and clinicopathologic factors were investigated according to receptor groups and whether the patients had received neoadjuvant chemotherapy. The three scoring methods showed differences in their associations with clinicopathologic factors in all subgroups studied. Positive PD-L1 expression by IC was significantly associated with worse overall survival in patients with neoadjuvant chemotherapy and showed a trend for worse overall survival and distant metastasis-free survival in triple-negative patients with neoadjuvant chemotherapy. Positive PD-L1 expression by TCIC and TC also showed trends for worse survival in different subgroups.

CONCLUSIONS

Our findings indicate that the three scoring methods with a 1% cutoff are different in their sensitivity for PD-L1 expression and their associations with clinicopathologic factors. Scoring by TCIC is the most sensitive way to identify PD-L1-positive breast cancer by immunohistochemistry. As a prognostic marker, our study suggests that PD-L1 is associated with worse clinical outcome, most often shown by the IC score; however, the other scores may also have clinical implications in some subgroups. Large clinical trials are needed to test the similarities and differences of these scoring methods for their predictive values in anti-PD-1/PD-L1 therapy.

Breast Cancer Immunotherapy: From Biology to Current Clinical Applications

Therapeutic strategies for the treatment of breast cancer have historically been determined by the presence or absence of hormone receptors and HER2 amplification and/or protein expression. For patients with breast cancer that lack these biomarkers, the so-called ‘triple-negative’ subtype, chemotherapy has been the cornerstone of cure and palliation. However, with the recent successful development of immune checkpoint molecules that target cytotoxic T-lymphocyte antigen-4, programmed cell death-1 (PD-1), and PD-ligand 1 (PD-L1), improved survival has been reported across a range of tumour types including melanoma, lung, and bladder cancer. In metastatic breast cancer, trials of single-agent immune checkpoint inhibitors (ICI) have resulted in limited overall response rates; however, strategies that combine local or systemic therapies with ICI have improved response rates and, in some cases, improved survival. For example, the addition of an anti-PD-L1 inhibitor, atezolizumab, to nab-paclitaxel chemotherapy for newly diagnosed metastatic triple-negative breast cancer demonstrated an improvement in overall survival in an informal analysis of the PD-L1-positive subset in a recently reported Phase III clinical trial. These results ultimately led to U.S. Food and Drug Administration (FDA) approval for an ICI for the treatment of breast cancer, with numerous other health authorities following suit. Herein, the authors describe the biology behind ICI, the rationale for ICI administration in breast cancer, the related clinical trial data reported to date, and promising future strategies.

Clinical Development of PD-1/PD-L1 Inhibitors in Breast Cancer: Still a Long Way to Go

OPINION STATEMENT

Currently, only patients with metastatic triple-negative breast cancer whose tumors are PD-L1 positive are eligible for receiving immunotherapy. Other studies have explored new combinations with PD-1/PD-L1 inhibitors in different disease settings and populations. Data from neoadjuvant trials testing the addition of PD-1/PD-L1 inhibitors to standard treatment are promising and have led to increases in pathologic complete response rates; however, data on survival outcomes are still immature. There is still much work needed to optimize benefits of immunotherapy in breast cancer and correlative studies in patients treated with immunotherapy are urgently needed to inform the best strategies for further development.

T-cell-based breast cancer immunotherapy

Cancer immunotherapy has witnessed a new renaissance with the advent of immune checkpoint inhibitors, which reactivate T cells and foster endogenous anti-tumor responses. The excellent results of immunotherapy in the field of melanoma, renal cancer, lung cancer, and other cancer types that have traditionally been known to be immunogenic, rekindled the interest of the oncology community in extending the benefits to all cancers including breast cancer (BC). In this review, we highlight the current state of using T cells as both markers for clinical practice and therapeutic options for BC.

The evolving management of metastatic triple negative breast cancer

Advanced triple negative breast cancer (TNBC) is an incurable disease classified by its lack of expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2. Due to its lack of therapeutic targets, it has historically been treated with single agent chemotherapy, with combination cytotoxic therapy typically reserved for patients with high disease burdens, symptomatic disease, and/or impending visceral crisis. Recent molecular analyses have revealed that this clinical group of TNBCs is in fact quite biologically heterogeneous, with multiple TNBC subtypes defined by distinct biology and clinical behavior. Building on this biology, 2 targeted strategies are now approved for selected patients with advanced TNBC: the poly (ADP-ribose) polymerase inhibitors for advanced TNBC with a germline mutation in BRCA1/2, and the combination of the programmed death ligand 1-specific antibody atezolizumab with nab-paclitaxel for advanced TNBC that expresses programmed death ligand 1 on immune cells within the tumor. These targeted agents tend to be associated with a more favorable side effect profile and longer disease control than standard chemotherapy. A number of other targeted therapies have shown promise in early clinical trials, and several are now in definitive phase 3 testing for advanced TNBC. These include the antiapoptotic kinase inhibitors ipatisertib and capivasertib, and the antibody-drug conjugate sacituzumab govitecan-hziy. Approved biomarker-driven treatment options for this disease are thus likely to expand in the near-term. Here we review current treatment options and emerging targeted therapies for advanced TNBC. For patients who do not meet criteria for approved targeted therapies, participation in clinical trials evaluating precision medicines with candidate predictive biomarkers in advanced TNBC should be encouraged.

Atezolizumab in the treatment of metastatic triple-negative breast cancer

INTRODUCTION

Triple-negative breast cancer (TNBC) accounts for approximately 10%-15% of all diagnosed breast cancers and is associated with an aggressive natural history and poor clinical outcomes. Immunotherapy using immune checkpoint inhibitors has emerged as an effective therapeutic option for TNBC. The results of the IMpassion130 trial have recently led to the approval of the combination of atezolizumab and nab-paclitaxel in the first-line treatment of patients with unresectable locally advanced or metastatic, PD-L1-positive TNBC.

AREAS COVERED

This article summarizes the clinical development and ongoing research on atezolizumab in the treatment of metastatic TNBC. Results of atezolizumab monotherapy trials and data from combination studies with chemotherapy in the advanced setting are reviewed, with special focus on the design, methods, and key findings of the IMpassion130 trial.

EXPERT OPINION

The approval of atezolizumab plus nab-paclitaxel represents an important advance in the treatment of metastatic TNBC. This combination has a favorable risk-benefit profile and is associated with clinically meaningful outcomes. However, further research is needed to identify better predictive biomarkers of response as well as novel immunotherapeutic strategies with atezolizumab and other anticancer drugs.

Triple negative breast cancer: special histological types and emerging therapeutic methods

Triple negative breast cancer (TNBC) is a complex and malignant breast cancer subtype that lacks expression of the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), thereby making therapeutic targeting difficult. TNBC is generally considered to have high malignancy and poor prognosis. However, patients diagnosed with certain rare histomorphologic subtypes of TNBC have better prognosis than those diagnosed with typical triple negative breast cancer. In addition, with the discovery and development of novel treatment targets such as the androgen receptor (AR), PI3K/AKT/mTOR and AMPK signaling pathways, as well as emerging immunotherapies, the therapeutic options for TNBC are increasing. In this paper, we review the literature on various histological types of TNBC and focus on newly developed therapeutic strategies that target and potentially affect molecular pathways or emerging oncogenes, thus providing a basis for future tailored therapies focused on the mutational aspects of TNBC.

Expanding the Role for Immunotherapy in Triple-Negative Breast Cancer

PD-1 axis blockade, in combination with chemotherapy, improves outcomes in advanced triple-negative breast cancer that is PD-L1 positive. The phase 3 KEYNOTE-522 trial now shows that the addition of pembrolizumab to chemotherapy improves pathological complete response rates regardless of PD-L1 status and appears to improve survival.

Effect of Pembrolizumab Plus Neoadjuvant Chemotherapy on Pathologic Complete Response in Women With Early-Stage Breast Cancer: An Analysis of the Ongoing Phase 2 Adaptively Randomized I-SPY2 Trial

Importance

Approximately 25% of patients with early-stage breast cancer who receive (neo)adjuvant chemotherapy experience a recurrence within 5 years. Improvements in therapy are greatly needed.

Objective

To determine if pembrolizumab plus neoadjuvant chemotherapy (NACT) in early-stage breast cancer is likely to be successful in a 300-patient, confirmatory randomized phase 3 neoadjuvant clinical trial.

Design, Setting, and Participants

The I-SPY2 study is an ongoing open-label, multicenter, adaptively randomized phase 2 platform trial for high-risk, stage II/III breast cancer, evaluating multiple investigational arms in parallel. Standard NACT serves as the common control arm; investigational agent(s) are added to this backbone. Patients with ERBB2 (formerly HER2)-negative breast cancer were eligible for randomization to pembrolizumab between November 2015 and November 2016.

Interventions

Participants were randomized to receive taxane- and anthracycline-based NACT with or without pembrolizumab, followed by definitive surgery.

Main Outcomes and Measures

The primary end point was pathologic complete response (pCR). Secondary end points were residual cancer burden (RCB) and 3-year event-free and distant recurrence-free survival. Investigational arms graduated when demonstrating an 85% predictive probability of success in a hypothetical confirmatory phase 3 trial.

Results

Of the 250 women included in the final analysis, 181 were randomized to the standard NACT control group (median [range] age, 47 [24.77] years). Sixty-nine women (median [range] age, 50 [27-71] years) were randomized to 4 cycles of pembrolizumab in combination with weekly paclitaxel followed by AC; 40 hormone receptor (HR)-positive and 29 triple-negative. Pembrolizumab graduated in all 3 biomarker signatures studied. Final estimated pCR rates, evaluated in March 2017, were 44% vs 17%, 30% vs 13%, and 60% vs 22% for pembrolizumab vs control in the ERBB2-negative, HR-positive/ERBB2-negative, and triple-negative cohorts, respectively. Pembrolizumab shifted the RCB distribution to a lower disease burden for each cohort evaluated. Adverse events included immune-related endocrinopathies, notably thyroid abnormalities (13.0%) and adrenal insufficiency (8.7%). Achieving a pCR appeared predictive of long-term outcome, where patients with pCR following pembrolizumab plus chemotherapy had high event-free survival rates (93% at 3 years with 2.8 years' median follow-up).

Conclusions and Relevance

When added to standard neoadjuvant chemotherapy, pembrolizumab more than doubled the estimated pCR rates for both HR-positive/ERBB2-negative and triple-negative breast cancer, indicating that checkpoint blockade in women with early-stage, high-risk, ERBB2-negative breast cancer is highly likely to succeed in a phase 3 trial. Pembrolizumab was the first of 10 agents to graduate in the HR-positive/ERBB2-negative signature.

Trial Registration

ClinicalTrials.gov Identifier: NCT01042379.

Microbiome, bile acids, and obesity: How microbially modified metabolites shape anti-tumor immunity

Bile acids (BAs) are known facilitators of nutrient absorption but recent paradigm shifts now recognize BAs as signaling molecules regulating both innate and adaptive immunity. Bile acids are synthesized from cholesterol in the liver with subsequent microbial modification and fermentation adding complexity to pool composition. Bile acids act on several receptors such as Farnesoid X Receptor and the G protein-coupled BA receptor 1 (TGR5). Interestingly, BA receptors (BARs) are expressed on immune cells and activation either by BAs or BAR agonists modulates innate and adaptive immune cell populations skewing their polarization toward a more tolerogenic anti-inflammatory phenotype. Intriguingly, recent evidence also suggests that BAs promote anti-tumor immune response through activation and recruitment of tumoricidal immune cells such as natural killer T cells. These exciting findings have redefined BA signaling in health and disease wherein they may suppress inflammation on the one hand, yet promote anti-tumor immunity on the other hand. In this review, we provide our readers with the most recent understanding of the interaction of BAs with the host microbiome, their effect on innate and adaptive immunity in health and disease with a special focus on obesity, bariatric surgery-induced weight loss, and immune checkpoint blockade in cancer.

The Landscape of Targeted Therapies in TNBC

Triple negative breast cancer (TNBC) constitutes the most aggressive molecular subtype among breast tumors. Despite progress on the underlying tumor biology, clinical outcomes for TNBC unfortunately remain poor. The median overall survival for patients with metastatic TNBC is approximately eighteen months. Chemotherapy is the mainstay of treatment while there is a growing body of evidence that targeted therapies may be on the horizon with poly-ADP-ribose polymerase (PARP) and immune check-point inhibitors already established in the treatment paradigm of TNBC. A large number of novel therapeutic agents are being evaluated for their efficacy in TNBC. As novel therapeutics are now incorporated into clinical practice, it is clear that tumor heterogeneity and clonal evolution can result to de novo or acquired treatment resistance. As precision medicine and next generation sequencing is part of cancer diagnostics, tailored treatment approaches based on the expression of molecular markers are currently being implemented in clinical practice and clinical trial design. The scope of this review is to highlight the most relevant current knowledge regarding underlying molecular profile of TNBC and its potential application in clinical practice.

Breast cancer immunology and immunotherapy: targeting the programmed cell death protein-1/programmed cell death protein ligand-1

Historically, breast cancer has been regarded as an immunogenic "cold" tumor. However, the discovery of immune checkpoint inhibitors has made immunotherapy becoming an emerging new treatment modality for breast cancer. This review discusses the immune system, immune features of breast cancer, and the programmed cell death protein-1/programmed cell death protein ligand-1 (PD-1/PD-L1) inhibitors used in the treatment of breast cancer. High T lymphocyte infiltration and mutation burden were observed in triple-negative breast cancer and human epidermal growth factor receptor 2 positive breast cancer. Increasing breast cancer immunogenicity and modulating the tumor microenvironment has been reported to improve the therapeutic efficacy of immunotherapy. Recent clinical trials involving PD-1/PD-L1 inhibitors monotherapy in breast cancer has revealed little efficacy, which highlights the need to develop combinations of PD-1/PD-L1 inhibitors with chemotherapy, molecularly targeted therapies, and other immunotherapies to maximize the clinical efficacy. Collectively, the immunotherapy might be a promising therapeutic strategy for breast cancer and several clinical trials are still on-going.

Molecular subtypes and precision treatment of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype. Despite the progress made in precision treatment of cancer patients, targeted treatment is still at its early stage in TNBC, and chemotherapy remains the standard treatment. With the advances in next generation sequencing technology, genomic and transcriptomic analyses have provided deeper insight into the inter-tumoral heterogeneity of TNBC. Much effort has been made to classify TNBCs into different molecular subtypes according to genetic aberrations and expression signatures and to uncover novel treatment targets. In this review, we summarized the current knowledge regarding the molecular classification of TNBC and explore the future paradigm for using molecular classification to guide the development of precision treatment and clinical practice.

Breast Cancer, Version 3.2020, NCCN Clinical Practice Guidelines in Oncology

Several new systemic therapy options have become available for patients with metastatic breast cancer, which have led to improvements in survival. In addition to patient and clinical factors, the treatment selection primarily depends on the tumor biology (hormone-receptor status and HER2-status). The NCCN Guidelines specific to the workup and treatment of patients with recurrent/stage IV breast cancer are discussed in this article.

Role of Immunotherapy in Triple-Negative Breast Cancer

Immune checkpoint inhibitors (ICIs) have led to durable clinical remissions in many metastatic cancers. However, the single-agent efficacy of ICIs in breast cancer is low, including in triple-negative breast cancer (TNBC), which has several key characteristics that enhance ICI responses. Strategies to improve anticancer immune responses in TNBC are urgently needed to extend survival for patients with metastatic disease. This review presents ICI monotherapy response rates and discusses combination strategies with chemotherapy, targeted therapies, and novel immunotherapies. It concludes with a summary of immunotherapy biomarkers in TNBC and a call to action for future directions of research critical to advancing the efficacy of immunotherapy for patients with TNBC.

Positive progress: current and evolving role of immune checkpoint inhibitors in metastatic triple-negative breast cancer

Background:

Triple-negative breast cancer (TNBC) represents an aggressive breast cancer subtype with historically poor overall outcomes, due primarily to a lack of effective targeted agents. Chemotherapy has been the primary treatment approach, although immune checkpoint inhibitors (ICIs) are currently being investigated to improve patient outcomes. This review examines the clinical implications of current evidence on the use of ICIs for the treatment of metastatic TNBC.

Methods:

Our systematic search identified two phase III and five phase I/II trials reporting on the efficacy of ICIs used as monotherapy or combined with chemotherapy for the treatment of metastatic TNBC.

Results:

The phase III IMpassion 130 trial showed a significant improvement in median progression-free survival in the intent-to-treat (net 1.7 months, p = 0.002) and PD-L1-positive populations (net 2.5 months, p < 0.001) for the addition of first-line atezolizumab versus placebo to nab-paclitaxel in metastatic TNBC. Although median overall survival was not significantly improved in patients receiving atezolizumab overall [net 2.3 months, hazard ratio (HR) 0.86, 95% confidence interval (CI) 0.72–1.02, p = 0.078], numerical improvements in the PD-L1-positive population were compelling (net 7.0 months, HR 0.71; 95% CI 0.54–0.93). Toxicity profiles were as expected, and no new safety signals were observed. Pembrolizumab monotherapy did not significantly improve overall survival in similar patients that had received prior treatment in KEYNOTE-119.

Conclusions:

Atezolizumab plus nab-paclitaxel represents a potential new first-line standard of care for patients with metastatic PD-L1-positive TNBC. Other ICIs used as monotherapy, or combined with chemotherapy for advanced TNBC, as well as their use for earlier stage disease, are areas of ongoing investigation.

Immuno-Oncology Biomarkers for Personalized Immunotherapy in Breast Cancer

The immune checkpoint blockade therapy has drastically advanced treatment of different types of cancer over the past few years. Female breast cancer is the second leading cause of death in the overall burden of cancers worldwide that is encouraging healthcare professionals to improve cancer care management. The checkpoint blockade therapies combined with novel agents become the recent focus of various clinical trials in breast cancer. However, identification of the patients who are responsive to these therapeutic strategies remained as a major issue for enhancing the efficacy of these treatments. This highlights the unmet need in discovery and development of novel biomarkers to add predictive values for prosperous personalized medicine. In this review we summarize the advances done in the era of biomarker studies and highlight their link in supporting breast cancer immunotherapy.

Multi-panel immunofluorescence analysis of tumor infiltrating lymphocytes in triple negative breast cancer: Evolution of tumor immune profiles and patient prognosis

The evolutionary changes in immune profiles of triple negative breast cancer (TNBC) are not well understood, although it is known that immune checkpoint inhibitors have diminished activity in heavily pre-treated TNBC patients. This study was designed to characterize immune profile changes of longitudinal tumor specimens by studying immune subsets of tumor infiltrating lymphocytes (TILs) in paired primary and metastatic TNBC in a cohort of "poor outcome" (relapsed within 5 years) patients. Immune profiles of TNBCs in a cohort of "good outcome" (no relapse within 5 years) patients were also analyzed. Immune subsets were characterized for CD4, CD8, FOXP3, CD20, CD33, and PD1 using immuno-fluorescence staining in stroma, tumor, and combined stroma and tumor tissue. TIL subsets in "good outcome" versus "poor outcome" patients were also analyzed. Compared with primary, metastatic TNBCs had significantly lower TILs by hematoxylin and eosin (H&E) staining. Stromal TILs (sTILs), but not tumoral TILs (tTILs) had significantly reduced cytotoxic CD8+ T cells (CTLs), PD1+ CTLs, and total PD1+ TILs in metastatic compared with matched primary TNBCs. Higher PD1+ CTLs, PD1+CD4+ helper T cells (PD1+TCONV) and all PD1+ T cells in sTILs, tTILs and total stromal and tumor TILS (s+tTIL) were all associated with better prognosis. In summary, TIL subsets decrease significantly in metastatic TNBCs compared with matched primary. Higher PD1+ TILs are associated with better prognosis in early stage TNBCs. This finding supports the application of immune checkpoint inhibitors early in the treatment of TNBCs.

Tissue-resident memory T cells in breast cancer control and immunotherapy responses

The presence of tumour-infiltrating lymphocytes (TILs) is associated with favourable outcomes in patients with breast cancer as well as in those with other solid tumours. T cells make up a considerable proportion of TILs and current evidence suggests that CD8⁺ T cells are a crucial determinant of favourable clinical outcomes. Studies involving tumour material from numerous solid tumour types, including breast cancer, demonstrate that the CD8⁺ TILs include a subpopulation of tissue-resident memory T (T_RM) cells. This subpopulation has features consistent with those of T_RM cells, which have been described as having a role in peripheral immune surveillance and viral immunity in both humans and mice. Patients with early-stage triple-negative breast cancers harbouring greater numbers of T_RM cells have a substantially improved prognosis and longer overall survival. Furthermore, patients with advanced-stage breast cancers with higher levels of T_RM cells have increased response rates to anti-PD-1 antibodies. These findings have motivated efforts to explore whether CD8⁺ T_RM cells include tumour-specific T cells, their functional responses to cognate antigens and their role in responses to immune checkpoint inhibition. In this Review, we focus on the clinical significance of CD8⁺ T_RM cells and the potential ways that these cells can be targeted to improve the success of immunotherapeutic approaches in patients with breast cancer, as well as in those with other solid tumour types.

Pembrolizumab for Early Triple-Negative Breast Cancer

BACKGROUND

Previous trials showed promising antitumor activity and an acceptable safety profile associated with pembrolizumab in patients with early triple-negative breast cancer. Whether the addition of pembrolizumab to neoadjuvant chemotherapy would significantly increase the percentage of patients with early triple-negative breast cancer who have a pathological complete response (defined as no invasive cancer in the breast and negative nodes) at definitive surgery is unclear.

METHODS

In this phase 3 trial, we randomly assigned (in a 2:1 ratio) patients with previously untreated stage II or stage III triple-negative breast cancer to receive neoadjuvant therapy with four cycles of pembrolizumab (at a dose of 200 mg) every 3 weeks plus paclitaxel and carboplatin (784 patients; the pembrolizumab-chemotherapy group) or placebo every 3 weeks plus paclitaxel and carboplatin (390 patients; the placebo-chemotherapy group); the two groups then received an additional four cycles of pembrolizumab or placebo, and both groups received doxorubicin-cyclophosphamide or epirubicin-cyclophosphamide. After definitive surgery, the patients received adjuvant pembrolizumab or placebo every 3 weeks for up to nine cycles. The primary end points were a pathological complete response at the time of definitive surgery and event-free survival in the intention-to-treat population.

RESULTS

At the first interim analysis, among the first 602 patients who underwent randomization, the percentage of patients with a pathological complete response was 64.8% (95% confidence interval [CI], 59.9 to 69.5) in the pembrolizumab-chemotherapy group and 51.2% (95% CI, 44.1 to 58.3) in the placebo-chemotherapy group (estimated treatment difference, 13.6 percentage points; 95% CI, 5.4 to 21.8; P<0.001). After a median follow-up of 15.5 months (range, 2.7 to 25.0), 58 of 784 patients (7.4%) in the pembrolizumab-chemotherapy group and 46 of 390 patients (11.8%) in the placebo-chemotherapy group had disease progression that precluded definitive surgery, had local or distant recurrence or a second primary tumor, or died from any cause (hazard ratio, 0.63; 95% CI, 0.43 to 0.93). Across all treatment phases, the incidence of treatment-related adverse events of grade 3 or higher was 78.0% in the pembrolizumab-chemotherapy group and 73.0% in the placebo-chemotherapy group, including death in 0.4% (3 patients) and 0.3% (1 patient), respectively.

CONCLUSIONS

Among patients with early triple-negative breast cancer, the percentage with a pathological complete response was significantly higher among those who received pembrolizumab plus neoadjuvant chemotherapy than among those who received placebo plus neoadjuvant chemotherapy. (Funded by Merck Sharp & Dohme [a subsidiary of Merck]; KEYNOTE-522 ClinicalTrials.gov number, NCT03036488.).

Atezolizumab for the treatment of breast cancer

Introduction: In March 2019, atezolizumab became the first immune checkpoint inhibitor to receive a breast cancer-specific approval. Based on a significant improvement in progression-free survival as well as a 10-month improvement in overall survival (on interim analysis) seen in the IMpassion 130 trial, the combination of atezolizumab and nab-paclitaxel was approved for patients with unresectable locally advanced or metastatic triple-negative breast cancer (TNBC).Areas covered: This article reviews current data and ongoing research on atezolizumab for the treatment of breast cancer. Results of atezolizumab monotherapy trials in the context of other early immune checkpoint blockade trials in breast cancer are discussed as well as data from combination clinical trials with chemotherapy in both early-stage and metastatic breast cancer. We focus on the safety and efficacy analyses from the phase III IMpassion trial that led to FDA and EMA approval of atezolizumab and nab-paclitaxel in patients whose tumor tested positive for PD-L1 by the Ventana SP142 companion diagnostic immunohistochemical assay.Expert opinion: The FDA and EMA approvals of atezolizumab mark an important advance for treatment of metastatic TNBC. However, ongoing investigations need to define better biomarkers of response, determine resistance mechanisms, and identify strategies to increase response rates.

Conducting a Virtual Clinical Trial in HER2-Negative Breast Cancer Using a Quantitative Systems Pharmacology Model With an Epigenetic Modulator and Immune Checkpoint Inhibitors

The survival rate of patients with breast cancer has been improved by immune checkpoint blockade therapies, and the efficacy of their combinations with epigenetic modulators has shown promising results in preclinical studies. In this prospective study, we propose an ordinary differential equation (ODE)-based quantitative systems pharmacology (QSP) model to conduct an in silico virtual clinical trial and analyze potential predictive biomarkers to improve the anti-tumor response in HER2-negative breast cancer. The model is comprised of four compartments: central, peripheral, tumor, and tumor-draining lymph node, and describes immune activation, suppression, T cell trafficking, and pharmacokinetics and pharmacodynamics (PK/PD) of the therapeutic agents. We implement theoretical mechanisms of action for checkpoint inhibitors and the epigenetic modulator based on preclinical studies to investigate their effects on anti-tumor response. According to model-based simulations, we confirm the synergistic effect of the epigenetic modulator and that pre-treatment tumor mutational burden, tumor-infiltrating effector T cell (Teff) density, and Teff to regulatory T cell (Treg) ratio are significantly higher in responders, which can be potential biomarkers to be considered in clinical trials. Overall, we present a readily reproducible modular model to conduct in silico virtual clinical trials on patient cohorts of interest, which is a step toward personalized medicine in cancer immunotherapy.

Pembrolizumab plus chemotherapy as neoadjuvant treatment of high-risk, early-stage triple-negative breast cancer: results from the phase 1b open-label, multicohort KEYNOTE-173 study

BACKGROUND

The phase Ib KEYNOTE-173 study was conducted to assess the safety and preliminary antitumor activity of neoadjuvant chemotherapy plus pembrolizumab in high-risk, early-stage, non-metastatic triple-negative breast cancer (TNBC).

PATIENTS AND METHODS

Six pembrolizumab plus chemotherapy regimens were evaluated (cohorts A-F). All cohorts received a pembrolizumab 200-mg run-in dose (cycle 1), then eight cycles of pembrolizumab in combination with a taxane with or without carboplatin for 12 weeks, and then doxorubicin and cyclophosphamide for an additional 12 weeks before surgery. Primary end points were safety and recommended phase II dose (RP2D); secondary end points were pathological complete response (pCR) rate, objective response rate, and event-free and overall survival. Exploratory end points were the relationship between outcome and potential biomarkers, such as tumor programmed death ligand 1 (PD-L1) expression (combined positive score) and stromal tumor-infiltrating lymphocyte levels (sTILs).

RESULTS

Sixty patients were enrolled between 18 February 2016, and 28 February 2017. Dose-limiting toxicities occurred in 22 patients, most commonly febrile neutropenia (n = 10 across cohorts). Four cohorts (B, C, D, F) did not meet the RP2D threshold; two cohorts did (A, E). The most common grade ≥3 treatment-related adverse event was neutropenia (73%). Immune-mediated adverse events and infusion reactions occurred in 18 patients (30%) and were grade ≥3 in six patients (10%). The pCR rate (ypT0/Tis ypN0) across all cohorts was 60% (range 49%-71%). Twelve-month event-free and overall survival rates ranged from 80% to 100% across cohorts (100% for four cohorts). Higher pre-treatment PD-L1 combined positive score, and pre- and on-treatment sTILs were significantly associated with higher pCR rates (P = 0.0127, 0.0059, and 0.0085, respectively).

CONCLUSION

Combination neoadjuvant chemotherapy and pembrolizumab for high-risk, early-stage TNBC showed manageable toxicity and promising antitumor activity. In an exploratory analysis, the pCR rate showed a positive correlation with tumor PD-L1 expression and sTIL levels.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02622074.

Phase II study of pembrolizumab and capecitabine for triple negative and hormone receptor-positive, HER2-negative endocrine-refractory metastatic breast cancer

BACKGROUND

Response rates to single agent immune checkpoint blockade in unselected pretreated HER2-negative metastatic breast cancer (MBC) are low. However, they may be augmented when combined with chemotherapy.

METHODS

We conducted a single-arm, phase II study of patients with triple negative (TN) or hormone receptor-positive endocrine-refractory (HR+) MBC who were candidates for capecitabine. Patients were treated with pembrolizumab 200 mg intravenously day 1 and capecitabine 1000 mg/m2 by mouth twice daily on days 1-14 of a 21-day cycle. The primary end point was median progression-free survival (mPFS) compared with historic controls and secondary end points were overall response rate (ORR), safety and tolerability. The study had 80% power to detect a 2-month improvement in mPFS with the addition of pembrolizumab over historic controls treated with capecitabine alone.

RESULTS

Thirty patients, 16 TN and 14 HR+ MBC, were enrolled from 2017 to 2018. Patients had a median age of 51 years and received a median of 1 (range 0-6) prior lines of therapy for MBC. Of 29 evaluable patients, the mPFS was 4.0 (95% CI 2.0 to 6.4) months and was not significantly longer than historic controls of 3 months. The median overall survival was 15.4 (95% CI 8.2 to 20.3) months. The ORR was 14% (n=4), stable disease (SD) was 41% (n=12) and clinical benefit rate (CBR=partial response+SD>6 months) was 28% (n=8). The ORR and CBR were not significantly different between disease subtypes (ORR 13% and 14%, CBR 25% and 29% for TN and HR+, respectively). The 1-year PFS rate was 20.7% and three patients have ongoing responses. The most common adverse events were low grade and consistent with those seen in MBC patients receiving capecitabine, including hand-foot syndrome, gastrointestinal symptoms, fatigue and cytopenias. Toxicities at least possibly from pembrolizumab included grade 3 or 4 liver test abnormalities (7%), rash (7%) and diarrhea (3%), as well as grade 5 hepatic failure in a patient with liver metastases.

CONCLUSIONS

Compared with historical controls, pembrolizumab with capecitabine did not improve PFS in this biomarker unselected, pretreated cohort. However, some patients had prolonged disease control.

TRIAL REGISTRATION NUMBER

NCT03044730.

A Phase II Study of Pembrolizumab in Combination With Palliative Radiotherapy for Hormone Receptor-positive Metastatic Breast Cancer

BACKGROUND

The purpose of this study was to investigate whether combining pembrolizumab with palliative radiation therapy (RT) improves outcomes in patients with hormone receptor-positive (HR⁺) metastatic breast cancer (MBC).

PATIENTS AND METHODS

Eligible patients had HR⁺/human epidermal growth factor receptor 2-negative MBC; were candidates for RT to ≥ 1 bone, soft tissue, or lymph node lesion; and had ≥ 1 lesion outside the RT field. Patients received 200 mg pembrolizumab intravenously 2 to 7 days prior to RT and on day 1 of repeating 21-day cycles. RT was delivered to a previously unirradiated area in 5 treatments each of 4 Gy. The primary endpoint was objective response rate. The study used a 2-stage design: 8 women were enrolled into the first stage, and if at least 1 of 8 patients experienced an objective response, 19 more would be enrolled. Secondary endpoints included progression-free survival, overall survival, and safety. Exploratory endpoints included association of overall response rate with programmed death-ligand 1 status and tumor-infiltrating lymphocytes.

RESULTS

Eight patients were enrolled in stage 1. The median age was 59 years, and the median prior lines of chemotherapy for metastatic disease was 2. There were no objective responses, and the study was closed to further accrual. The median progression-free survival was 1.4 months (95% confidence interval, 0.4-2.1 months), and the median overall survival was 2.9 months (95% confidence interval, 0.9-3.6 months). All-cause adverse events occurred in 87.5% of patients, including just 1 grade 3 event (elevation of aspartate aminotransferase).

CONCLUSIONS

RT combined with pembrolizumab did not produce an objective response in patients with heavily pre-treated HR⁺ MBC. Future studies should consider alternative radiation dosing and fractionation in patients with less heavily pre-treated HR⁺ MBC.