Assessment of PD-L1 expression and tumor-infiltrating lymphocytes (TILs) across molecular subtypes of triple-negative breast cancer

Advancements in clinical research and emerging therapies for triple-negative breast cancer treatment

Triple-negative breast cancer (TNBC), defined by the lack of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 (HER2) expression, is acknowledged as the most aggressive form of breast cancer (BC), comprising 15%-20% of all primary cases. Despite the prevalence of TNBC, effective and well-tolerated targeted therapies remain limited, with chemotherapy continuing to be the mainstay of treatment. However, the horizon is brightened by recent advancements in immunotherapy and antibody-drug conjugates (ADCs), which have garnered the U.S. Food and Drug Administration (FDA) approval for various stages of TNBC. Poly (ADP-ribose) polymerase inhibitors (PARPi), particularly for TNBC with BRCA mutations, present a promising avenue, albeit with the challenge of resistance that must be addressed. The success of phosphoinositide-3 kinase (PI3K) pathway inhibitors in hormone receptor (HR)-positive BC suggests potential applicability in TNBC, spurring optimism within the research community. This review endeavors to offer a comprehensive synthesis of both established and cutting-edge targeted therapies for TNBC. We delve into the specifics of PARPi, androgen receptor (AR) inhibitors, Cancer stem cells (CSCs), PI3K/Protein Kinase B (AKT)/mammalian target of rapamycin (mTOR), the transforming growth factor-beta (TGF-β), Ntoch, Wnt/β-catenin, hedgehog (Hh) pathway inhibitors, Epigenetic target-mediated drug delivery, ADCs, immune checkpoint inhibitors (ICIs)and novel immunotherapeutic solutions, contextualizing TNBC within current treatment paradigms. By elucidating the mechanisms of these drugs and their prospective clinical applications, we aim to shed light on the challenges and underscore the beacon of hope that translational research and innovative therapies represent for the oncology field.

Classifications of triple-negative breast cancer: insights and current therapeutic approaches

Triple-negative breast cancer (TNBC) is an aggressive and challenging type of cancer, characterized by the absence of specific receptors targeted by current therapies, which limits effective targeted treatment options. TNBC has a high risk of recurrence and distant metastasis, resulting in lower survival rates. Additionally, TNBC exhibits significant heterogeneity at histopathological, proteomic, transcriptomic, and genomic levels, further complicating the development of effective treatments. While some TNBC subtypes may initially respond to chemotherapy, resistance frequently develops, increasing the risk of aggressive recurrence. Therefore, precisely classifying and characterizing the distinct features of TNBC subtypes is crucial for identifying the most suitable molecular-based therapies for individual patients. In this review, we provide a comprehensive overview of these subtypes, highlighting their unique profiles as defined by various classification systems. We also address the limitations of conventional therapeutic approaches and explore innovative biological strategies, all aimed at advancing the development of targeted and effective therapeutic strategies for TNBC.

Evolving Management of Breast Cancer in the Era of Predictive Biomarkers and Precision Medicine

Breast cancer is the most common cancer among women in the world as well as in the United States. Molecular and histological differentiation have helped clinicians optimize treatments with various therapeutics, including hormonal therapy, chemotherapy, immunotherapy, and radiation therapy. Recently, immunotherapy has become the standard of care in locally advanced triple-negative breast cancer and an option across molecular subtypes for tumors with a high tumor mutation burden. Despite the advancements in personalized medicine directing the management of localized and advanced breast cancers, the emergence of resistance to these therapies is the leading cause of death among breast cancer patients. Therefore, there is a critical need to identify and validate predictive biomarkers to direct treatment selection, identify potential responders, and detect emerging resistance to standard therapies. Areas of active scientific and clinical research include novel personalized and predictive biomarkers incorporating tumor microenvironment, tumor immune profiling, molecular characterization, and histopathological differentiation to predict response and the potential emergence of resistance.

Emerging treatment approaches for triple-negative breast cancer

Approximately, 15% of global breast cancer cases are diagnosed as triple-negative breast cancer (TNBC), identified as the most aggressive subtype due to the simultaneous absence of estrogen receptor, progesterone receptor, and HER2. This characteristic renders TNBC highly aggressive and challenging to treat, as it excludes the use of effective drugs such as hormone therapy and anti-HER2 agents. In this review, we explore standard therapies and recent emerging approaches for TNBC, including PARP inhibitors, immune checkpoint inhibitors, PI3K/AKT pathway inhibitors, and cytotoxin-conjugated antibodies. The mechanism of action of these drugs and their utilization in clinical practice is explained in a pragmatic and prospective manner, contextualized within the current landscape of standard therapies for this pathology. These advancements present a promising frontier for tailored interventions with the potential to significantly improve outcomes for TNBC patients. Interestingly, while TNBC poses a complex challenge, it also serves as a paradigm and an opportunity for translational research and innovative therapies in the field of oncology.

Predictive Biomarkers for Response to Immunotherapy in Triple Negative Breast Cancer: Promises and Challenges

Triple negative breast cancer (TNBC) is a highly heterogeneous disease with a poor prognosis and a paucity of therapeutic options. In recent years, immunotherapy has emerged as a new treatment option for patients with TNBC. However, this therapeutic evolution is paralleled by a growing need for biomarkers which allow for a better selection of patients who are most likely to benefit from this immune checkpoint inhibitor (ICI)-based regimen. These biomarkers will not only facilitate a better optimization of treatment strategies, but they will also avoid unnecessary side effects in non-responders, and limit the increasing financial toxicity linked to the use of these agents. Huge efforts have been deployed to identify predictive biomarkers for the ICI, but until now, the fruits of this labor remained largely unsatisfactory. Among clinically validated biomarkers, only programmed death-ligand 1 protein (PD-L1) expression has been prospectively assessed in TNBC trials. In addition to this, microsatellite instability and a high tumor mutational burden are approved as tumor agnostic biomarkers, but only a small percentage of TNBC fits this category. Furthermore, TNBC should no longer be approached as a single biological entity, but rather as a complex disease with different molecular, clinicopathological, and tumor microenvironment subgroups. This review provides an overview of the validated and evolving predictive biomarkers for a response to ICI in TNBC.

Highlights of the 17th St Gallen International Breast Cancer Conference 2021: customising local and systemic therapies

The 17th edition of the St Gallen International Breast Cancer Conference was held in March 2021 in an entirely virtual mode. More than 3,300 participants took part in this important bi-annual critical review of the ‘state of the art’ in the multidisciplinary care of early-stage breast cancer (BC). Seventy-four experts from all continents discussed and commented on the previously elaborated consensus questions as well as numerous interrogations on early-BC diagnosis and treatment asked by the audience. The theme of this year’s Conference was ‘Customising local and systemic therapies’. This paper summarises the results of the 2021 international panel votes as a quick news update. We discuss the most important issues on genetics, pathology, surgery, radiotherapy and systemic therapies presented and debated throughout the conference. We selected the topics based on applicability into the personalised care of BC patients and focused on questions that have a clear impact on our current clinical practice.