Updates in Systemic Treatment of Hormone Receptor-Positive Early-Stage Breast Cancer.

OPINION STATEMENT: Hormone-receptor positive (HR +) and human epidermal growth factor receptor 2 (HER2) negative early breast cancer (eBC) is a heterogeneous disease with several contributing factors for increased risk of recurrence, including tumor features, individual biomarkers, and genomic risk. The current standard approach in the management of HR + /HER2neg eBC includes chemotherapy and endocrine therapy (ET), and additional therapies based on risk profile, menopausal status, and genetics are sometimes appropriate. The risk of recurrence is more pronounced in patients with high-risk eBC including large tumor size, nodal involvement, high proliferative index, and genetic predisposition. In premenopausal patients with high-risk eBC, ovarian function suppression in combination with adjuvant ET improves survival. In postmenopausal patients, extended aromatase inhibitor (AI) therapy can be considered. Recent trials have identified novel treatment approaches to reduce the risk of recurrence in high-risk HR + /HER2neg eBC including the addition of cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors to adjuvant ET. For patients with germline BRCA1/BRCA2 mutations, adjuvant poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors have been shown to improve overall survival (OS). However, despite these recent advances, the risk of recurrence remains substantial, highlighting an area of unmet need. There are several ongoing clinical trials further investigating the role of CDK 4/6 inhibitors and immunotherapy in high-risk HR + /HER2neg eBC.

Improving Outcomes for Women With Metastatic HER2-Positive and HER2-Low Breast Cancer.

At JADPRO Live 2023, presenters discussed recent updates to clinical practice in metastatic HER2-positive metastatic breast cancer. During the session, they reviewed review recent FDA approvals, the clinical relevance of HER2-low status, and evidence-based practices for managing adverse events associated with novel HER2 agents.

Investigating the Salience of Clinical Meaningfulness and Clinically Meaningful Outcomes in Metastatic Breast Cancer Care Delivery.

PURPOSE: As metastatic breast cancer (mBC) treatment evolves, there is a need to understand how clinical meaningfulness, or a meaningful change in a patient's daily life, and clinically meaningful outcomes inform patient-centered care. Partnering with key stakeholders ensures patient-centered research incorporates the knowledge and expertise of advisors with lived experience. We describe a multistakeholder engagement approach to examine how people living with mBC (PLWmBC), caregivers, and health care providers interpret clinical meaningfulness and clinically meaningful outcomes and their influence on mBC treatment decision making and care. METHODS: Qualitative focus groups with PLWmBC, caregivers, and health care providers were conducted and analyzed along three overarching themes: interpretations of clinical meaningfulness and clinically meaningful outcomes; treatment recommendations, preferences, and decisions; and implications for clinical practice. Patient-led and professional organizations served as research partners in study design, implementation, and interpretation of findings. RESULTS: Partnerships were established with four patient-led and three professional organizations representing diverse constituencies throughout the United States. Twenty-two focus groups were conducted with 50 PLWmBC, 24 caregivers, and 41 health care providers (oncologists, n = 11; advanced practice providers, n = 13; oncology nurses, n = 17) between March and June 2023. PLWmBC and caregivers were unfamiliar with the concepts of clinical meaningfulness and clinically meaningful outcomes. Although health care providers were familiar, they did not use the terms when discussing treatment with PLWmBC. Across groups, participants emphasized the importance of meaningful outcomes beyond overall survival, including quality of life and improvement in symptoms and functioning. Participants noted that outcomes considered meaningful are individualized and dynamic. CONCLUSION: This study offers insight into how partnering with patient advocacy and professional organizations can enhance research quality and aid translation of findings to clinical practice, thereby supporting patient-centered care.

Role of [18F]FDG PET/CT in patients with invasive breast carcinoma of no special type: Literature review and comparison between guidelines.

PURPOSE: The recently released EANM/SNMMI guideline, endorsed by several important clinical and imaging societies in the field of breast cancer (BC) care (ACR, ESSO, ESTRO, EUSOBI/ESR, EUSOMA), emphasized the role of [18F]FDG PET/CT in management of patients with no special type (NST) BC. This review identifies and summarizes similarities, discrepancies and novelties of the EANM/SNMMI guideline compared to NCCN, ESMO and ABC recommendations. METHODS: The EANM/SNMMI guideline was based on a systematic literature search and the AGREE tool. The level of evidence was determined according to NICE criteria, and 85 % agreement or higher was reached regarding each statement. Comparisons with NCCN, ESMO and ABC guidelines were examined for specific clinical scenarios in patients with early stage through advanced and metastatic BC. RESULTS: Regarding initial staging of patients with NST BC, [18F]FDG PET/CT is the preferred modality in the EANM-SNMMI guideline, showing superiority as a single modality to a combination of contrast-enhanced CT of thorax-abdomen-pelvis plus bone scan in head-to-head comparisons and a randomized study. Its use is recommended in patients with clinical stage IIB or higher and may be useful in certain stage IIA cases of NST BC. In NCCN, ESMO, and ABC guidelines, [18F]FDG PET/CT is instead recommended as complementary to conventional imaging to solve inconclusive findings, although ESMO and ABC also suggest [18F]FDG PET/CT can replace conventional imaging for staging patients with high-risk and metastatic NST BC. During follow up, NCCN and ESMO only recommend diagnostic imaging if there is suspicion of recurrence. Similarly, EANM-SNMMI states that [18F]FDG PET/CT is useful to detect the site and extent of recurrence only when there is clinical or laboratory suspicion of recurrence, or when conventional imaging methods are equivocal. The EANM-SNMMI guideline is the first to emphasize a role of [18F]FDG PET/CT for assessing early metabolic response to primary systemic therapy, particularly for HER2+ BC and TNBC. In the metastatic setting, EANM-SNMMI state that [18F]FDG PET/CT may help evaluate bone metastases and determine early response to treatment, in agreement with guidelines from ESMO. CONCLUSIONS: The recently released EANM/SNMMI guideline reinforces the role of [18F]FDG PET/CT in the management of patients with NST BC supported by extensive evidence of its utility in several clinical scenarios.

Genomic and transcriptomic landscape of HER2-low breast cancer.

BACKGROUND: Novel agents have expanded the traditional HER2 definitions to include HER2-Low (HER2L) Breast Cancer (BC). We sought to evaluate the distinct molecular characteristics of HER2L BC to understand potential clinical/biologic factors driving resistance and clinical outcomes. METHODS: Retrospective analysis was performed on 13,613 BC samples, tested at Caris Life Sciences via NextGen DNA/RNA Sequencing. BC subtypes were defined by IHC/ISH. CODEai database was used to access clinical outcomes from insurance claims data. RESULTS: Overall, mutational landscape was similar between HER2L and classical subsets of HR+and HRneg cohorts. TP53 mutations were significantly higher in HRneg/HER2L group vs. HR+/HER2L tumors (p<0.001). A higher mutation rate of PIK3CA was observed in HRneg/HER2L tumors compared to TNBC subtype (p=0.016). PD-L1 positivity was elevated in HRneg/HER2L tumors compared to HR+/HER2L tumors, all p<0.01. Patients with HR+/HER2L tumors treated with CDK4/6 inhibitors had similar OS compared to pts with HR+/HER2-0 (HR=0.89, p=0.012). 27.2% of HR+/HER2L pts had activating PIK3CA mutations. Among HR+PIK3CA mutated tumors, HER2L pts treated with alpelisib showed no difference in OS vs. HER2-0 alpelisib-treated pts (HR=1.23, p=0.517). 13.9% of HER2L TNBC pts were PD-L1+. Interestingly, pts with PD-L1+ HER2L/HRneg (TNBC) treated with immune checkpoint inhibitors (ICI) showed improved OS than HER2-0 TNBC (HR=0.61, p=0.046). CONCLUSION: Our findings expand the understanding of the molecular profile of the HER2L subgroup and comparison to the classically defined breast cancer subgroups. Genomic risk assessments after progression on novel therapeutics can be assessed to better define implications for mechanisms of resistance.

Joint EANM-SNMMI guideline on the role of 2-[18F]FDG PET/CT in no special type breast cancer : (endorsed by the ACR, ESSO, ESTRO, EUSOBI/ESR, and EUSOMA).

INTRODUCTION: There is much literature about the role of 2-[18F]FDG PET/CT in patients with breast cancer (BC). However, there exists no international guideline with involvement of the nuclear medicine societies about this subject. PURPOSE: To provide an organized, international, state-of-the-art, and multidisciplinary guideline, led by experts of two nuclear medicine societies (EANM and SNMMI) and representation of important societies in the field of BC (ACR, ESSO, ESTRO, EUSOBI/ESR, and EUSOMA). METHODS: Literature review and expert discussion were performed with the aim of collecting updated information regarding the role of 2-[18F]FDG PET/CT in patients with no special type (NST) BC and summarizing its indications according to scientific evidence. Recommendations were scored according to the National Institute for Health and Care Excellence (NICE) criteria. RESULTS: Quantitative PET features (SUV, MTV, TLG) are valuable prognostic parameters. In baseline staging, 2-[18F]FDG PET/CT plays a role from stage IIB through stage IV. When assessing response to therapy, 2-[18F]FDG PET/CT should be performed on certified scanners, and reported either according to PERCIST, EORTC PET, or EANM immunotherapy response criteria, as appropriate. 2-[18F]FDG PET/CT may be useful to assess early metabolic response, particularly in non-metastatic triple-negative and HER2+ tumours. 2-[18F]FDG PET/CT is useful to detect the site and extent of recurrence when conventional imaging methods are equivocal and when there is clinical and/or laboratorial suspicion of relapse. Recent developments are promising. CONCLUSION: 2-[18F]FDG PET/CT is extremely useful in BC management, as supported by extensive evidence of its utility compared to other imaging modalities in several clinical scenarios.

Emerging pharmacotherapy trends in preventing and managing oral mucositis induced by chemoradiotherapy and targeted agents.

INTRODUCTION: The introduction of targeted therapy and immunotherapy has tremendously changed the clinical outcomes and prognosis of cancer patients. Despite innovative pharmacological therapies and improved radiotherapy (RT) techniques, patients continue to suffer from side effects, of which oral mucositis (OM) is still the most impactful, especially for quality of life. AREAS COVERED: We provide an overview of current advances in cancer pharmacotherapy and RT, in relation to their potential to cause OM, and of the less explored and more recent literature reports related to the best management of OM. We have analyzed natural/antioxidant agents, probiotics, mucosal protectants and healing coadjuvants, pharmacotherapies, immunomodulatory and anticancer agents, photobiomodulation and the impact of technology. EXPERT OPINION: The discovery of more precise pathophysiologic mechanisms of CT and RT-induced OM has outlined that OM has a multifactorial origin, including direct effects, oxidative damage, upregulation of immunologic factors, and effects on oral flora. A persistent upregulated immune response, associated with factors related to patients' characteristics, may contribute to more severe and long-lasting OM. The goal is strategies to conjugate individual patient, disease, and therapy-related factors to guide OM prevention or treatment. Despite further high-quality research is warranted, the issue of prevention is paramount in future strategies.

Fulfilling the Role of a Parent While Undergoing Treatment for Cancer: A Review of the Literature and the Potential Impact of Childcare Support on Cancer Outcomes.

Breast cancer is the most prevalent malignancy among adolescents and young adults (AYAs). Despite the efficacy of chemotherapy, AYA patients contend with psychosocial challenges, including psychological distress and financial toxicity, exacerbated further by those with dependent children. Parenting responsibilities intersect with cancer care, impacting both family dynamics and treatment adherence. Despite recognized needs, however, the impact of parenting concerns or even parenting status and the presence of dependents has not been systematically addressed and there is a paucity of interventional research regarding patients with cancer as concomitant caregivers. A feasibility study conducted by the Brown University Oncology Cooperative Group demonstrated the potential benefits of providing financial assistance for childcare, both improving treatment adherence and reducing distress among participants. Similar interventions have shown promise in addressing financial hardships for AYA patients with cancer who are concomitant caregivers. Ultimately, parenting concerns have a significant impact on medical decision-making, and further interventional research on childcare support is required to examine the ways in which health systems can improve family stability, stress, and quality of life.

The Genomic, Transcriptomic, and Immunologic Landscape of HRAS Mutations in Solid Tumors.

Tipifarnib is the only targeted therapy breakthrough for HRAS-mutant (HRASmt) recurrent or metastatic head and neck squamous cell carcinoma (HNSCC). The molecular profiles of HRASmt cancers are difficult to explore given the low frequency of HRASmt. This study aims to understand the molecular co-alterations, immune profiles, and clinical outcomes of 524 HRASmt solid tumors including urothelial carcinoma (UC), breast cancer (BC), non-small-cell lung cancer (NSCLC), melanoma, and HNSCC. HRASmt was most common in UC (3.0%), followed by HNSCC (2.82%), melanoma (1.05%), BC (0.45%), and NSCLC (0.44%). HRASmt was absent in Her2+ BC regardless of hormone receptor status. HRASmt was more frequently associated with squamous compared to non-squamous NSCLC (60% vs. 40% in HRASwt, p = 0.002). The tumor microenvironment (TME) of HRASmt demonstrated increased M1 macrophages in triple-negative BC (TNBC), HNSCC, squamous NSCLC, and UC; increased M2 macrophages in TNBC; and increased CD8+ T-cells in HNSCC (all p < 0.05). Finally, HRASmt was associated with shorter overall survival in HNSCC (HR: 1.564, CI: 1.16-2.11, p = 0.003) but not in the other cancer types examined. In conclusion, this study provides new insights into the unique molecular profiles of HRASmt tumors that may help to identify new targets and guide future clinical trial design.

Tissue-specific thresholds of mutation burden associated with anti-PD-1/L1 therapy benefit and prognosis in microsatellite-stable cancers.

Immune checkpoint inhibitors (ICIs) targeting programmed cell death protein 1 or its ligand (PD-1/L1) have expanded the treatment landscape against cancers but are effective in only a subset of patients. Tumor mutation burden (TMB) is postulated to be a generic determinant of ICI-dependent tumor rejection. Here we describe the association between TMB and survival outcomes among microsatellite-stable cancers in a real-world clinicogenomic cohort consisting of 70,698 patients distributed across 27 histologies. TMB was associated with survival benefit or detriment depending on tissue and treatment context, with eight cancer types demonstrating a specific association between TMB and improved outcomes upon treatment with anti-PD-1/L1 therapies. Survival benefits were noted over a broad range of TMB cutoffs across cancer types, and a dose-dependent relationship between TMB and outcomes was observed in a subset of cancers. These results have implications for the use of cancer-agnostic and universal TMB cutoffs to guide the use of anti-PD-1/L1 therapies, and they underline the importance of tissue context in the development of ICI biomarkers.

Evaluating Patient Experience in a Multidisciplinary Breast Cancer Clinic: A Prospective Study.

Background: Multidisciplinary clinics (MDCs) are a care model in which patients see several physicians across specialties and/or other allied health professionals in a single appointment in a shared space. This study sought to better understand patients' experiences with breast cancer (BC) MDC. Methods: A total of 429 patients diagnosed with BC and seen in a MDC between November 2020 and November 2021 were invited to participate in a patient experience survey. Results: In total, 116 patient respondents (27%) with representative demographics described their experience. Most patients report feeling "somewhat prepared" for the BC MDC experience (67%, median = 3.7, interquartile range [IQR] = 1.9), but with variability. The major areas of positive feedback were that the MDC was convenient (89.3%), efficient use of time (65.2%), and a good way to get questions answered (65.2%). Major criticisms included that the MDC was overwhelming (16.1%) and/or too long (4.5%). When asked to rate the top three satisfaction areas of MDCs, patients chose seeing multiple providers during a single visit (80.4%), communication about the process before and throughout the MDC (48.2%), and inclusivity of their support system (38.4%). The highest rated dissatisfiers were the volume of information presented (42.9%) and patients' emotional comfort (anxiety/stress) during MDC appointment (30.2%). Overall, 83% of patients with BC rate the MDC experience as excellent (median = 4.8, IQR = 0.9) and would be "very likely" to recommend BC MDC (median = 4.8, IQR = 0.9). Conclusion: Patients value seeing multiple providers simultaneously in an environment inclusive of their support systems, which is described as convenient and efficient. Improving emotional distress is a key opportunity to improve patient experience.

Exploring DESTINY: the Past, Present, and Future of Trastuzumab Deruxtecan.

PURPOSE OF REVIEW: HER2-positive breast cancer accounts for 10-15% of all breast cancers and fam-trastuzumab deruxtecan (T-DXd) has played a major role in moving the treatment of HER2-expressing disease forward. RECENT FINDINGS: T-DXd is a novel antibody-drug conjugate (ADC) composed of a humanized IgG1 monoclonal antibody against HER2 receptor bound to a potent topoisomerase I cytotoxin payload by a cleavable peptide linker. It has been shown to have robust preclinical activity in pretreated cancer cell lines, as well as meaningful clinical activity in advanced HER2-expressing breast cancer. Recent studies have demonstrated T-DXd as an active agent for metastatic HER2-positive patients, and as a viable additional line for heavily pretreated patients with HER2-low disease. The toxicity of T-DXd remains manageable and burden of side effects seems to be lower when offered as an earlier line of therapy over the course of treatment. In this review, we discuss the pharmacology of T-DXd, review pertinent preclinical and clinical data, and address potential challenges and future directions related to the use of T-DXd in clinical practice.

Sequencing Antibody Drug Conjugates in Breast Cancer: Exploring Future Roles.

Antibody drug conjugates (ADCs) have emerged as a highly effective treatment strategy across breast cancer (BC) subtypes, including human epidermal growth factor receptor 2-positive (HER2+), hormone-receptor positive (ER/PR+), and triple-negative breast cancer (TNBC). Over the past twenty years, ADCs have undergone relevant evolutions, from target diversity to payload ratio, to linker design, allowing for a progressive increase in their efficacy. From the first-generation ADC, trastuzumab emtansine (T-DM1), approved in 2013 for HER2+ breast cancer, to next generation ADCs such as sacituzumab govitecan and trastuzumab deruxtecan, to emerging ADCs on the horizon, we continue to see unparalleled efficacy compared to traditional chemotherapy. However, each ADC has brought a new cadre of adverse events for clinicians and patients to manage. Importantly, with the development and approval of several ADCs to treat metastatic breast cancer, there are unanswered clinical questions surrounding how to optimally sequence treatment for patients who may be candidates for more than one ADC and, in general, how to treat patients beyond progression on ADCs. From bench to bedside, in this review, we will discuss the pharmacology and current indications for the novel ADCs trastuzumab deruxtecan and sacituzumab govitecan. Highlighting emerging ADCs and ongoing clinical trials, we will anticipate the changes in the breast cancer treatment paradigm. Lastly, we will outline the available data and current approaches for adverse event management and sequencing strategies for ADCs in clinical practice, including proposed mechanisms of resistance.

Sequencing systemic therapy in hormone-receptor positive metastatic breast cancer: a modern paradigm.

Deaths from metastatic breast cancer continue to be a leading cause of global cancer mortality among women. The pace of advances in the treatment of hormone-receptor positive metastatic breast cancer (HR+ MBC) has introduced nuance and complexity in choosing between available agents as patients and physicians explore options across lines of therapy. In this review, we explore the modern paradigm of treatment options and the sequential approach to HR+ MBC, as well as treatment options on the horizon, and the particular impact on survival outcomes and the associated adverse effects of those treatments. We discuss the diagnostic approach, first- and second-line management, as well as management of later-line endocrine-refractory HR+ MBC. Treatments discussed include cyclin-dependent kinase 4/6 inhibitors, antibody drug conjugates, and targeted therapies against phosphatidylinositol-4,5-bisphosphate-3-kinase catalytic subunit alpha (PIK3CA), estrogen receptor 1 (ESR1), and poly[ADP-ribose] polymerase (PARP), among others. Building from the initial diagnostic approach, we describe how to pragmatically layer options by appropriate line of therapy and personalized drivers of disease to aid in treatment decision making step-by-step. Combining sequential treatment options, evolving treatment options, and advanced genetic and genomic testing along with shared decision making between patients and physicians, this review aims to outline the key factors that ultimately drive the decisions for treatment in hormone-positive metastatic breast cancer.

The Careers and Professional Well-Being of Women Oncologists During the COVID-19 Pandemic: Responding for Tomorrow.

The COVID-19 pandemic exacerbated gender inequity in medicine, with women physicians reporting greater household responsibilities than their men counterparts and steeper barriers to career advancement. The pandemic highlighted the systemic assumptions and challenges faced by women physicians, which we anticipate is also true in our field of oncology. Prior literature suggests that women physicians were tasked with increased personal and professional responsibilities without compensation for their additional work, as well as derailments in career progression and significant burnout. Our aims are to highlight areas of opportunity to optimize the workplace experience of the oncology workforce and to invest in the professional well-being and sustainability of women oncologists as a step toward global workplace equity and future pandemic preparedness.

Newly Approved and Emerging Agents in HER2-Positive Metastatic Breast Cancer.

Human epidermal growth factor receptor 2-positive breast cancer (HER2+ BC) is an aggressive tumor type, accounting for 15% to 20% of the approximately 300,000 new BC cases in the United States each year. The goal of this review is to discuss the evolving landscape of therapies for HER2+ metastatic BC (mBC). Targeted therapies that have been the standard of care (SOC) for HER2+ mBC for almost a decade have greatly improved patient outcomes. The SOC for the first-line treatment of HER2+ mBC continues to be HER2-targeted monoclonal antibodies (mAbs) + a taxane, but recent updates in the second-line setting favor use of a newer HER2-targeted antibody-drug conjugate (ADC), trastuzumab deruxtecan, versus the prior SOC ADC, trastuzumab emtansine. Numerous options are now available in the third line and beyond, including tyrosine kinase inhibitor (TKI) regimens, newer mAbs, and other ADCs. The optimal course of treatment for individual patients can be guided by location of metastases, prior therapies, concomitant biomarkers, and monitoring and management of adverse events. Ongoing trials will further the evolution of the HER2+ mBC treatment landscape. Furthermore, next-generation ADCs, TKIs, and classes of drugs that have not been approved for the treatment of HER2+ mBC, including immune checkpoint inhibitors and cyclin-dependent kinase 4 and 6 inhibitors, are also being evaluated for their efficacy in the first and second line. Although the influx of new drugs may complicate treatment decisions for physicians, having a multitude of options will undoubtedly further improve patient outcomes and patient-centered care.

Triple-negative Breast Carcinoma With Apocrine and Histiocytoid Features: A Clinicopathologic and Molecular Study of 18 Cases.

Triple-negative breast cancer (TNBC) is a heterogenous group of tumors. Most TNBCs are high-grade aggressive tumors, but a minority of TNBCs are not high grade, with relatively indolent behavior and specific morphologic and molecular features. We performed a clinicopathologic and molecular assessment of 18 non-high-grade TNBCs with apocrine and/or histiocytoid features. All were grade I or II with low Ki-67 (≤20%). Thirteen (72%) showed apocrine features, and 5 (28%) showed histiocytoid and lobular features. In all, 17/18 expressed the androgen receptor, and 13/13 expressed gross cystic disease fluid protein 15. Four (22.2%) patients were treated with neoadjuvant chemotherapy, but none achieved a pathologic complete response. In all, 2/18 patients (11%) had lymph node metastasis at the time of surgery. None of the cases had a recurrence or disease-specific death, with an average follow-up time of 38 months. Thirteen cases were profiled by targeted capture-based next-generation DNA sequencing. Genomic alterations (GAs) were most significant for PI3K-PKB/Akt pathway (69%) genes, including PIK3R1 (23%), PIK3CA (38%), and PTEN (23%), and RTK-RAS pathway (62%) including FGFR4 (46%) and ERBB2 (15%). TP53 GA was seen in only 31% of patients. Our findings support those on high-grade TNBCs with apocrine and/or histiocytoid features as a clinicopathologic and genetically distinct subgroup of TNBC. They can be defined by features including tubule formation, rare mitosis, low Ki-67 (≤20%), triple-negative status, expression of androgen receptor and/or gross cystic disease fluid protein 15, and GA in the PI3K-PKB/Akt and/or RTK-RAS pathway. These tumors are not sensitive to chemotherapy but have favorable clinical behavior. Tumor subtype definitions are the first step to implementing future trial designs to select these patients.

PET/CT in Patients with Breast Cancer Treated with Immunotherapy.

Significant advances in breast cancer (BC) treatment have been made in the last decade, including the use of immunotherapy and, in particular, immune checkpoint inhibitors that have been shown to improve the survival of patients with triple negative BC. This narrative review summarizes the studies supporting the use of immunotherapy in BC. Furthermore, the usefulness of 2-deoxy-2-[18F]fluoro-D-glucose (2-[18F]FDG) positron emission/computerized tomography (PET/CT) to image the tumor heterogeneity and to assess treatment response is explored, including the different criteria to interpret 2-[18F]FDG PET/CT imaging. The concept of immuno-PET is also described, by explaining the advantages of mapping treatment targets with a non-invasive and whole-body tool. Several radiopharmaceuticals in the preclinical phase are referred too, and, considering their promising results, translation to human studies is needed to support their use in clinical practice. Overall, this is an evolving field in BC treatment, despite PET imaging developments, the future trends also include expanding immunotherapy to early-stage BC and using other biomarkers.