Delayed diagnosis and increased mortality risk: Assessing the effects of the COVID-19 pandemic on breast cancer recurrence.

OBJECTIVES: The COVID-19 pandemic has had a significant global impact since its declaration in March 2020. The COVID-19 pandemic has disproportionately impacted cancer patients, particularly those with breast cancer. This study aims to analyze the effects of the pandemic on women diagnosed with breast cancer recurrence. METHODS: A cohort study was conducted at a tertiary public hospital in São Paulo State, Brazil. Data were collected from electronic records. Patients diagnosed with breast cancer and experiencing recurrence between January 2011 and March 2022 were included. Survival analysis was performed using the Kaplan-Meier estimator and Cox regression. RESULTS: The study included 187 patients, 45 in the pandemic group (recurrence after March 23, 2020) and 142 in the pre-pandemic group. Distant recurrences were more frequent in both groups (pre-pandemic: 62.7 %, pandemic: 75.5 %). Compared to the pre-pandemic group (1.8 years), the pandemic group experienced a longer mean time to recurrence detection (2.9 years) and significantly decreased median survival (9 months vs. 22 months). The Cox regression analysis confirmed an increased risk of death for women diagnosed with breast cancer recurrence during the pandemic period (HR = 1.92, 95 % CI 1.19‒3.12). CONCLUSION: The present study is among the first to investigate the pandemic's specific effects on breast cancer recurrence, revealing concerning delays in detection and a decrease in survival rates. Prompt diagnosis, timely treatment initiation, and comprehensive support are crucial during public health crises. These findings urge healthcare systems to prioritize tailored care for breast cancer patients during pandemics.

Converging and evolving immuno-genomic routes toward immune escape in breast cancer.

The interactions between tumor and immune cells along the course of breast cancer progression remain largely unknown. Here, we extensively characterize multiple sequential and parallel multiregion tumor and blood specimens of an index patient and a cohort of metastatic triple-negative breast cancers. We demonstrate that a continuous increase in tumor genomic heterogeneity and distinct molecular clocks correlated with resistance to treatment, eventually allowing tumors to escape from immune control. TCR repertoire loses diversity over time, leading to convergent evolution as breast cancer progresses. Although mixed populations of effector memory and cytotoxic single T cells coexist in the peripheral blood, defects in the antigen presentation machinery coupled with subdued T cell recruitment into metastases are observed, indicating a potent immune avoidance microenvironment not compatible with an effective antitumor response in lethal metastatic disease. Our results demonstrate that the immune responses against cancer are not static, but rather follow dynamic processes that match cancer genomic progression, illustrating the complex nature of tumor and immune cell interactions.

What Do the Transcriptome and Proteome of Menstrual Blood-Derived Mesenchymal Stem Cells Tell Us about Endometriosis?

Given the importance of menstrual blood in the pathogenesis of endometriosis and the multifunctional roles of menstrual mesenchymal stem cells (MenSCs) in regenerative medicine, this issue has gained prominence in the scientific community. Moreover, recent reviews highlight how robust the integrated assessment of omics data are for endometriosis. To our knowledge, no study has applied the multi-omics approaches to endometriosis MenSCs. This is a case-control study at a university-affiliated hospital. MenSCs transcriptome and proteome data were obtained by RNA-seq and UHPLC-MS/MS detection. Among the differentially expressed proteins and genes, we emphasize ATF3, ID1, ID3, FOSB, SNAI1, NR4A1, EGR1, LAMC3, and ZFP36 genes and MT2A, TYMP, COL1A1, COL6A2, and NID2 proteins that were already reported in the endometriosis. Our functional enrichment analysis reveals integrated modulating signaling pathways such as epithelial-mesenchymal transition (↑) and PI3K signaling via AKT to mTORC1 (↓ in proteome), mTORC1 signaling, TGF beta signaling, TNFA signaling via NFkB, IL6 STAT3 signaling, and response to hypoxia via HIF1A targets (↑ in transcriptome). Our findings highlight primary changes in the endometriosis MenSCs, suggesting that the chronic inflammatory endometrial microenvironment can modulate these cells, providing opportunities for endometriosis etiopathogenesis. Moreover, they identify challenges for future research leveraging knowledge for regenerative and precision medicine in endometriosis.

10-year opportunistic mammographic screening scenario in Brazil and its impact on breast cancer early detection: a nationwide population-based study.

Background: Mammographic screening has been used to reduce breast cancer mortality worldwide and remains the main modality for the early detection of this disease. Women from low- and middle-income countries still lack access to periodic mammograms and efficient health care. This cross-sectional study aimed to explore opportunistic mammographic coverage in Brazil, while considering the privately insured population and its association with early breast cancer (EBC) detection. Methods: Data on population, gross domestic product (GDP), number of mammograms performed under the Sistema Único de Saúde (SUS) public health system or private system, and women diagnosed with early-stage breast cancer from 2010 to 2019 were retrieved from publicly available databases. Results: A total of 39 555 636 mammograms with an average of 3 955 564 ± 395 704 mammograms were obtained per year from 2010 to 2019 in Brazil. Most examinations (58.6%) were performed in the target population (50-69 years old), while 32% were performed in women aged 40-49, and 9.4% were performed in women <40 years or >70 years of age. The 10-year mammogram coverage was 30.6% in the target population and 24.8% in the population aged 40-49 years, with significant variation across states and municipalities. The overall EBC detection rates in Brazil were 30.6% in populations aged 50-70 and 24.8% in those aged 40-50 years. We observed a positive correlation between coverage and EBC detection rate (r = 0.68; P = 0.0001 (50-70 years) and r = 0.75; P < 0.0001 (40-50 years)). According to the GDP, the municipalities with higher GDP per capita had higher mammogram coverage (P < 0.0001). Conclusions: The coverage of mammographic screening for women under the SUS is far below the international guidelines. Additionally, a significant number of mammograms have been performed in non-target populations. This scenario reflects the problematic screening programs in developing countries and reflects low rates of EBC diagnosis. As Brazil is a continental country with heterogeneous socioeconomic indicators, we observed significant variations in the number of mammograms performed by age groups when separated by states and municipalities. Even when considering supplemental health system coverage, municipalities with higher GDP per capita were associated with higher mammogram coverage.

Mastalgia in medical students: a prospective and multicentric study

Introduction: Mastalgia or breast pain affects most women, especially those of reproductive age. Of organic or nonorganic cause and variable intensity, it is related to factors such as hormonal, dietary, metabolic, and emotional changes, making it difficult to understand its pathophysiology and the definition of care conduct. It can influence the quality of life. The aim of this study was to identify, classify, and know the treatments and their effectiveness for breast pain in university students, relating their interference in the quality of life. Methods: A total of 1,064 students from two medical schools in the interior of São Paulo were interviewed and evaluated using a standardized and specific questionnaire with the aim of characterizing breast pain. Results: Mastalgia was reported in 1,034 students (p=0.0003), body mass index >25 increased breast tenderness by 4.3 times (RR=4.3; p=0.001; 95%CI 2.5­6.73), and sedentary lifestyle increased by 10.82 times (p=0.02). It was more common in the premenstrual cycle (p=0.002), and the greater the intensity, the smaller the number of students who performed the self-examination (p=0.02). The greater the pain, the greater the chance of being absent from classes (RR=15.82; p=0.0003; 95%CI 13.23­17.3). Drug treatment was applied in 15.54% of the cases, with satisfactory results in 92.16% of them (p=0.000004). Conclusions: The study showed a high incidence of breast pain in medical students, impairing their academic activities, making it clear the importance of investigating any symptom related to the hormonal axis and showing significant efficiency of the pharmacological treatment.

Axillary ultrasound and fine-needle aspiration cytology to predict clinically relevant nodal burden in breast cancer patients.

BACKGROUND: Axillary lymph node involvement is one important prognostic factor in breast cancer, but the way to access this information has been modified over the years. This study evaluated if axillary ultrasound (US) coupled with fine-needle aspiration cytology (FNAC) can accurately predict clinically relevant node metastasis in patients with breast cancer, and thus assist clinical decisions METHODS: This is a cross-sectional study with retrospective data collection of 241 individuals (239 women and 2 men) with unilateral operable breast cancer who were submitted to preoperative axillary assessment by physical exam, US and FNAC if suspicious nodes by imaging. We calculated sensitivity, specificity, and accuracy of the methods. We compared the patient's characteristics using chi-square test, parametrics and non-parametrics statistics according to the variable. RESULTS: The most sensible method was US (0.59; 95% CI, 0.50-0.69), and the most specific was US coupled with FNAC (0.97; 95% CI, 0.92-0.99). Only 2.7% of the patients with normal axillary US had more than 2 metastatic nodes in the axillary lymph node dissection, against 50% of the patients with suspicious lymph nodes in the US and positive FNAC. CONCLUSIONS: Axillary US coupled with FNAC can sort patients who have a few metastatic nodes at most from those with heavy axillary burden and could be one more tool to initially evaluate patients and define treatment strategies.

A propensity score-matched case-control study of laparoscopy and laparotomy for endometrial cancer.

OBJECTIVE: A surgery is essential for the management of early endometrial carcinoma. Due to the comorbidities associated with the disease, the complications of surgery are common. Laparoscopic surgery may reduce surgical complications but also have oncological risks. We aimed to compare recurrence and overall survival (OS) associated with laparoscopy and laparotomy for early endometrial cancer. METHODS: We included women treated for presumed early endometrial carcinoma at the Clinics Hospital of Ribeirão Preto Medical School from January 1998 to December 2017. We designed a 1:2 propensity score-matched case-control and compared the patients' characteristics, short-term outcomes, recurrence, and OS. RESULTS: A total of 252 women were included in this study, 168 underwent laparotomy, and 84 underwent laparoscopy. The two groups were well balanced according to most of the variables, and obesity was a characteristic of patients in both groups. Laparoscopy was associated with increased surgical time (194.7 min vesus 165.6 min; p<0.001) and reduced rate of surgical complications (6.5% versus 0; p=0.038). Laparoscopic surgery was not associated with the risk of tumor recurrence (HR: 0.41, 95%CI 0.14-1.19, p=0.100) or all-cause mortality (HR: 0.49, 95%CI 0.18-1.35, p=0.170). CONCLUSION: Laparoscopy was safe in terms of oncological outcomes and was associated with a lower rate of surgical complications. Our data support the use of minimally invasive surgery as the preferential approach in the management of early endometrial carcinoma.

The temporal mutational and immune tumour microenvironment remodelling of HER2-negative primary breast cancers.

The biology of breast cancer response to neoadjuvant therapy is underrepresented in the literature and provides a window-of-opportunity to explore the genomic and microenvironment modulation of tumours exposed to therapy. Here, we characterised the mutational, gene expression, pathway enrichment and tumour-infiltrating lymphocytes (TILs) dynamics across different timepoints of 35 HER2-negative primary breast cancer patients receiving neoadjuvant eribulin therapy (SOLTI-1007 NEOERIBULIN-NCT01669252). Whole-exome data (N = 88 samples) generated mutational profiles and candidate neoantigens and were analysed along with RNA-Nanostring 545-gene expression (N = 96 samples) and stromal TILs (N = 105 samples). Tumour mutation burden varied across patients at baseline but not across the sampling timepoints for each patient. Mutational signatures were not always conserved across tumours. There was a trend towards higher odds of response and less hazard to relapse when the percentage of subclonal mutations was low, suggesting that more homogenous tumours might have better responses to neoadjuvant therapy. Few driver mutations (5.1%) generated putative neoantigens. Mutation and neoantigen load were positively correlated (R2 = 0.94, p = <0.001); neoantigen load was weakly correlated with stromal TILs (R2 = 0.16, p = 0.02). An enrichment in pathways linked to immune infiltration and reduced programmed cell death expression were seen after 12 weeks of eribulin in good responders. VEGF was downregulated over time in the good responder group and FABP5, an inductor of epithelial mesenchymal transition (EMT), was upregulated in cases that recurred (p < 0.05). Mutational heterogeneity, subclonal architecture and the improvement of immune microenvironment along with remodelling of hypoxia and EMT may influence the response to neoadjuvant treatment.

Eutopic endometrium from women with endometriosis and chlamydial endometritis share immunological cell types and DNA repair imbalance: A transcriptome meta-analytical perspective.

The aim of this study was to identify the key similarities between the eutopic endometrium of women with endometriosis and chlamydia-induced endometritis taking into account tissue microenvironment heterogeneity, transcript gene profile, and enriched pathways. A meta-analysis of whole transcriptome microarrays was performed using publicly available data, including samples containing both glandular and stromal endometrial components. Control samples were obtained from women without any reported pathological condition. Only samples obtained during the proliferative menstrual phase were included. Cellular tissue heterogeneity was predicted using a method that integrates gene set enrichment and deconvolution approaches. The batch effect was estimated by principal variant component analysis and removed using an empirical Bayes method. Differentially expressed genes were identified using an adjusted p-value < 0.05 and fold change = 1.5. The protein-protein interaction network was built using the STRING database and interaction score over 400. The Molecular Signatures Database was used to analyse the functional enrichment analysis. Both conditions showed similarities in cell types in the microenvironment, particularly CD4+ and CD8+ Tem cells, NKT cells, Th2 cells, basophils, and eosinophils. With regards to the regulation of cellular senescence and DNA integrity/damage checkpoint, which are commonly enriched pathways, 21 genes were down-regulated and directly related to DNA repair. Compared to the endometriosis samples, some chlamydial endometritis samples presented a lack of enriched immune pathways. Our results suggest that both conditions show similar distributions of microenvironment cell types, the downregulation of genes involved in DNA repair and cell cycle control, and pathways involved in immune response evasion.

Epidemiological Analyses Reveal a High Incidence of Breast Cancer in Young Women in Brazil.

PURPOSE: Breast cancer screening is not recommended for young women (< 40 years old); therefore, those diagnosed are more likely to have advanced and metastatic disease, reducing treatment outcomes. This study aimed to investigate breast cancer epidemiology among young women in Brazil. METHODS: Data from three publicly available databases and a cohort from a university hospital in Brazil were analyzed in a retrospective study. Descriptive statistics was performed on disease prevalence and stage distribution across age groups. Incidence was estimated using age-standardized incidence ratio. The impact of age in disease-specific survival was also analyzed. RESULTS: Invasive breast cancer prevalence data by age group revealed that 4.4% and 20.6% of patients were < 35 and < 45 years old, respectively. In the United States, this prevalence was 1.85% and 11.5%, respectively (odds ratio [OR], 2.2; P < .0001). The percentage of regional and metastatic diseases were higher in São Paulo State (Fundação Oncocentro de São Paulo [FOSP]) compared with the United States (45% and 9.8% v 29% and 5.7%, respectively; P < .0001). In FOSP, regional and metastatic disease prevalence were higher among young patients (53.5% and 11.3%, respectively). The median tumor size in patients < 40 years old was higher (25.0 mm × 20.9 mm; P < .0001), and young patients have higher risk to be diagnosed with positive lymph nodes (OR, 1.5; P = .004) and higher proportion of luminal-B and triple-negative (TNBC) tumors. Young patients have a poor disease-specific survival because of late-stage diagnosis and more aggressive breast cancer subtypes (human epidermal growth factor receptor 2-enriched and TNBC) (P < .0001). CONCLUSION: In Brazil, breast cancer prevalence among young patients and late-stage incidence during this age span is higher. Advanced disease and more aggressive subtypes lead to a significant impact on breast cancer-specific survival in young patients.

Analysis of the relationship between hospital characteristics and survival in ovarian cancer: A historical cohort.

BACKGROUND AND OBJECTIVES: The management of ovarian cancer requires complex surgical and medical interventions. Specialized care is associated with superior outcomes in early and advanced stages. This study aimed to estimate the effect of hospital characteristics on the overall survival of women with epithelial ovarian cancer. METHODS: We established a cohort with data recorded by the Fundação Oncocentro de São Paulo cancer registry. We included 6111 women treated for ovarian cancer in the state of Sao Paulo from January 2000 to December 2018. From 76 hospitals analyzed, 7 were high volume (20 or more cases a year) and 69 low volume. Twenty-nine were teaching and 47 community hospitals. A 10-year survival was analyzed using the Kaplan-Meyer estimator and the Cox model. RESULTS: Fifty-two percent of the epithelial ovarian cancer patients were treated in high-volume hospitals. High-volume - (HR, 0.86; 95% CI, 0.8-0.92; P < .001) and teaching - (HR, 0.91; 95% CI, 0.85-0.99; P = .019) were hospital characteristics associated with low risk of death in 10 years. CONCLUSIONS: High-volume and teaching hospitals are associated with better overall survival in ovarian cancer. Our data suggest that both hospital characteristics are important indicators of good quality of care in ovarian cancer treatment.

Clinical and pathological associations of PTEN expression in ovarian cancer: a multicentre study from the Ovarian Tumour Tissue Analysis Consortium.

BACKGROUND: PTEN loss is a putative driver in histotypes of ovarian cancer (high-grade serous (HGSOC), endometrioid (ENOC), clear cell (CCOC), mucinous (MOC), low-grade serous (LGSOC)). We aimed to characterise PTEN expression as a biomarker in epithelial ovarian cancer in a large population-based study. METHODS: Tumours from 5400 patients from a multicentre observational, prospective cohort study of the Ovarian Tumour Tissue Analysis Consortium were used to evaluate associations between immunohistochemical PTEN patterns and overall survival time, age, stage, grade, residual tumour, CD8+ tumour-infiltrating lymphocytes (TIL) counts, expression of oestrogen receptor (ER), progesterone receptor (PR) and androgen receptor (AR) by means of Cox proportional hazard models and generalised Cochran-Mantel-Haenszel tests. RESULTS: Downregulation of cytoplasmic PTEN expression was most frequent in ENOC (most frequently in younger patients; p value = 0.0001) and CCOC and was associated with longer overall survival in HGSOC (hazard ratio: 0.78, 95% CI: 0.65-0.94, p value = 0.022). PTEN expression was associated with ER, PR and AR expression (p values: 0.0008, 0.062 and 0.0002, respectively) in HGSOC and with lower CD8 counts in CCOC (p value < 0.0001). Heterogeneous expression of PTEN was more prevalent in advanced HGSOC (p value = 0.019) and associated with higher CD8 counts (p value = 0.0016). CONCLUSIONS: PTEN loss is a frequent driver in ovarian carcinoma associating distinctly with expression of hormonal receptors and CD8+ TIL counts in HGSOC and CCOC histotypes.

Transcriptome meta-analysis reveals differences of immune profile between eutopic endometrium from stage I-II and III-IV endometriosis independently of hormonal milieu.

Eutopic endometrium appears to be crucial for endometriosis development. Despite of the evident importance, data regarding the cellular microenvironment remain unclear. Our objective was to explore the tissue microenvironment heterogeneity, transcripts, and pathways that are enriched in all phases of the menstrual cycle by analysing publicly deposited data derived from whole transcriptome microarrays of eutopic endometria of women with and without endometriosis. A meta-analysis of the transcriptome microarrays was performed using raw data available from a public database. Eligibility criteria included eutopic endometrium samples from women with endometriosis and healthy controls without any pathological condition reported the presence of an adequately reported normal menstrual phase, and samples containing both glandular and stromal components. Raw data were processed using a robust multiarray average method to provide background correction, normalisation, and summarisation. The batch effect was estimated by principal variant component analysis and removed using an empirical Bayes method. Cellular tissue heterogeneity was inferred using the xCell package. Differentially expressed genes were identified based on a 5% adjusted p value and a 2.0-fold change. Pathways were identified by functional enrichment based on the Molecular Signatures Database, a p value of < 5%, and an FDR q value of ≤ 25%. Genes that were more frequently found in pathways were identified using leading edge analysis. In a manner independent of cycle phase, the subpopulations of activated dendritic cells, CD4 T effector memory phenotype cells, eosinophils, macrophages M1, and natural killer T cells (NKT) were all higher in stage I-II endometriosis compared to those in healthy controls. The subpopulations of M2 macrophages and natural killer T cells were elevated in eutopic endometriums from women with stage III-IV endometriosis, and smooth muscle cells were always more prevalent in healthy eutopic endometriums. Among the differently expressed genes, FOS, FOSB, JUNB, and EGR1 were the most frequently mapped within the interaction networks, and this was independent of stage and cycle phase. The enriched pathways were directly related to immune surveillance, stem cell self-renewal, and epithelial mesenchymal transition. PI3K AKT mTOR, TGF signalling, and interferon alpha/gamma responses were enriched exclusively in stage III-IV endometriosis. The cellular microenvironments and immune cell profiles were different between eutopic endometriums from women with stage I-II and stage III-IV endometriosis, and these differences were independent of the hormonal milieu. Specifically, a pro-inflammatory profile was predominant in stage I-II endometriosis, and M1-M2 polarization into eutopic endometrium may be crucial for the progression of the disease. The higher prevalence of NKT cells in eutopic endometriums from women with endometriosis that was independent of cycle phase or staging suggested a sustained stress and/or damage to these eutopic endometriums. Based on this, the results of this meta-analysis are important for identifying challenges and opportunities for future research.

CAIX is a predictor of pathological complete response and is associated with higher survival in locally advanced breast cancer submitted to neoadjuvant chemotherapy.

BACKGROUND: Locally advanced breast cancer often undergoes neoadjuvant chemotherapy (NAC), which allows in vivo evaluation of the therapeutic response. The determination of the pathological complete response (pCR) is one way to evaluate the response to neoadjuvant chemotherapy. However, the rate of pCR differs significantly between molecular subtypes and the cause is not yet determined. Recently, the metabolic reprogramming of cancer cells and its implications for tumor growth and dissemination has gained increasing prominence and could contribute to a better understanding of NAC. Thus, this study proposed to evaluate the expression of metabolism-related proteins and its association with pCR and survival rates. METHODS: The expression of monocarboxylate transporters 1 and 4 (MCT1 and MCT4, respectively), cluster of differentiation 147 (CD147), glucose transporter-1 (GLUT1) and carbonic anhydrase IX (CAIX) was analyzed in 196 locally advanced breast cancer samples prior to NAC. The results were associated with clinical-pathological characteristics, occurrence of pCR, disease-free survival (DFS), disease-specific survival (DSS) and overall survival (OS). RESULTS: The occurrence of pCR was higher in the group of patients whith tumors expressing GLUT1 and CAIX than in the group without expression (27.8% versus 13.1%, p = 0.030 and 46.2% versus 13.5%, p = 0.007, respectively). Together with regional lymph nodes staging and mitotic staging, CAIX expression was considered an independent predictor of pCR. In addition, CAIX expression was associated with DFS and DSS (p = 0.005 and p = 0.012, respectively). CONCLUSIONS: CAIX expression was a predictor of pCR and was associated with higher DFS and DSS in locally advanced breast cancer patients subjected to NAC.

The Genomic and Immune Landscapes of Lethal Metastatic Breast Cancer.

The detailed molecular characterization of lethal cancers is a prerequisite to understanding resistance to therapy and escape from cancer immunoediting. We performed extensive multi-platform profiling of multi-regional metastases in autopsies from 10 patients with therapy-resistant breast cancer. The integrated genomic and immune landscapes show that metastases propagate and evolve as communities of clones, reveal their predicted neo-antigen landscapes, and show that they can accumulate HLA loss of heterozygosity (LOH). The data further identify variable tumor microenvironments and reveal, through analyses of T cell receptor repertoires, that adaptive immune responses appear to co-evolve with the metastatic genomes. These findings reveal in fine detail the landscapes of lethal metastatic breast cancer.

Mammography Coverage and Tumor Stage in the Opportunistic Screening Context.

INTRODUCTION: The increment of breast cancer screening coverage should lead to an increase in the proportion of early tumors diagnosed and the decrease of the cancer-related mortality. However, the effectiveness of opportunistic mammography screening is not well documented for public health systems in middle-income countries. PATIENTS AND METHODS: We conducted an ecologic study to evaluate the association of mammography coverage with trends in breast cancer stage distribution. We used data from a total of 42,850 breast cancer patients, diagnosed between 2000 and 2016, combined with estimated mammography coverage from 3 surveys (2003, 2008, and 2013). RESULTS: Biannual mammography coverage increased from 62.4% in 2003 to 73.9% in 2013. From 2000 to 2016, the proportion of in situ tumors increased 6.9%, the proportion of localized tumors increased 3.9%, the proportion of regional tumors decreased 6.9% and the frequency of distant tumors decreased 4% (P < .00001). CONCLUSION: Mammography coverage in the context of opportunistic breast cancer screening was associated with the increase of in situ and localized tumors and decrease of regional and distant tumors.

Development of New Formulations of Biologics: Expectations, Immunogenicity, and Safety for Subcutaneous Trastuzumab.

Subcutaneous (SC) trastuzumab has long been approved as a cancer treatment for early and advanced HER2-positive (HER2+) breast cancer by both the European Medicines Agency (EMA) and Agência Nacional de Vigilância Sanitária (ANVISA), the Brazilian National Health Surveillance Agency. A pivotal non-inferiority phase III trial, which aimed to provide a more convenient and cost-effective treatment in the HER2+ breast cancer neoadjuvant setting, showed that the SC group met prespecified efficacy endpoints and the SC formulation was considered as safe as the intravenous (IV) formulation. Considering the recent approval of several biosimilars, new SC formulations are also an interesting manufacturer strategy as these drugs can obtain patent protection. Despite being considered non-inferior to the IV formulation of trastuzumab, in clinical development, the SC formulation elicited higher immunogenicity, mainly related to overall anti-drug antibodies (ADAs); however, this finding was classified as clinically non-significant. In this article, we explore different aspects of the benefits and risks of the SC trastuzumab formulation according to published data.