npj Breast Cancer

Purpose: Cyclin-dependent kinase 4/6 inhibitors in combination with endocrine therapy have become widely adopted as a first-line treatment approach for hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC). Through a collaboration between Novartis and the US Food and Drug Administration, we integrated multimodal data from phase III MONALEESA trials to identify novel prognostic factors for HR+/HER2- ABC. Experimental Design: Baseline clinical and genomics data were collected from patients in the MONALEESA-2, -3, and -7 trials. Circulating tumor DNA (ctDNA) from plasma samples and gene expression in archival tumor biopsies were analyzed. Machine learning models were trained (n = 1,355) on progression-free survival (PFS) using multimodal features via fusion models. In a test set (n = 382), prognostic performances were evaluated using the Kaplan-Meier, Cox, and Weibull models. Results: The late fusion model achieved a prognostic performance (C-index: 0.727, 95% CI: 0.641-0.799) slightly outperforming early fusion (C-index: 0.718, 95% CI: 0.631-0.791) and single-modality models. Model-based risk stratification identified distinct low- and high-risk groups (PFS HR, 0.28; 95% CI: 0.20-0.38). Among the top 40 features for progression risk (18 clinical, 20 gene expression, and 2 ctDNA), these were associated with higher risk: liver involvement, higher histological grades, early relapse; lower STC2 and RBBP8 expressions and higher FBX05 expression; and higher tumor mutational burden and ctDNA purity. Conclusions: Integrating clinical and genomic modalities improved progression risk prediction compared with single-modality models, while highlighting salient features that inform the underlying biology and support hypothesis generation.

Neutrophils are increasingly recognized as key players in cancer progression, yet their functional heterogeneity limits their therapeutic exploitation. In breast cancer (BC), elevated circulating and tumor-associated neutrophils have been associated with poor prognosis, and low-density neutrophils (LDN), particularly, have been linked to immunosuppression. However, the specific neutrophil subsets driving these effects remain undefined. Here, we identify a previously unrecognized CCR4-expressing neutrophil subset, strongly enriched among LDN, whose frequency rises with disease stage and correlates with faster progression and shorter survival. Serial blood sampling further showed that CCR4+LDN levels fluctuate in line with clinical course, with increases indicating near-term risk in metastatic patients. Our findings also reveal that this subset has an immunosuppressive signature more pronounced than that of the remaining LDN, migrates preferentially toward tumor-derived chemokines, and dampens T cell-driven tumor killing even when PD-1 is blocked. Additionally, in a pilot cohort of Triple-Negative BC patients on anti-PD-1 therapy, early changes in this population were associated with treatment outcome. Together, these results reveal a distinct neutrophil population that actively contributes to immune escape and tumor progression, establishing CCR4+LDN as a minimally invasive real-time biomarker of disease course and treatment response, and as a promising target for neutrophil-directed therapies in BC.

Background: Patients with ER-positive/HER2-negative early breast cancer of low or intermediate grade are generally considered to have a favourable prognosis, yet a number will recur. This risk is poorly captured by standard clinicopathological factors. AI-based medical devices for whole slide image (WSI) analyses used for risk-stratification often predict on slide-level thereby overlooking spatial localisation of the biomarkers. We hypothesise that the spatial distribution of a previously reported AI-based marker provides independent prognostic value beyond its global score. Patients and Methods: This Swedish multicentre cohort study includes 6106 patients with primary invasive breast cancer: 3078 from the Stockholm region (training) and 3028 from Skane (independent test). Tile-level high-grade morphology scores were generated with ViT_DG, a vision-transformer adaptation of DeepGrade, and the presence of clusters of high-risk tiles localised at the invasive tumour front was defined as a binary biomarker. Primary analyses were pre-specified in the ER-positive/HER2-negative/lymph-node-negative and Grade 1-2 subgroup. Association with breast-cancer recurrence-free interval (BCRFI) and distant metastasis were assessed using multivariable Cox proportional hazards models (HR). Results: In the primary subgroup (n=1536 training; n=1403 test), tumour front clusters were present in 37% and 39% of patients. Cluster-positive status was associated with a 2.30-fold increased risk in the external test. Cluster-negative patients achieved a 10-year BCRFI of 95.3%, equivalent to Grade 1 patients and better than Grade 2 (92.4%), whereas cluster-positive patients (90.2%) did worse than the Grade 3 reference. The association was retained in patients classified as low-risk by ViT_DG (test set multivariable HR 2.86), identifying high-risk patients not captured by the global score. Conclusions: The absence of high-risk morphology clusters at the tumour front is an independent prognostic indicator, identifying a low-risk group independently of the global AI biomarker classification. More broadly, preserving the spatial distribution of AI-derived predictions enables prognostic stratification beyond slide-level aggregation.

Poly (ADP-ribose) polymerase inhibitors (PARPi) are the only targeted treatment available for early triple-negative breast cancer (TNBC), an aggressive subtype with limited treatment options. While PARPi are effective in patients with BRCA mutations, resistance to these inhibitors can arise. We previously developed BRCA-mutant cell lines, HCC1395, with acquired resistance to talazoparib and olaparib, and have now developed PARPi-resistant MX1 cell lines in an analogous manner. Ribosomal pathways were upregulated in 3/4 cell lines with acquired PARPi resistance. The resistant cell lines showed high and low basal nucleolar stress based on nucleolar morphology and nucleophosmin delocalization from nucleolus to nucleoplasm. Treatment of these cell lines with the combination of olaparib and a ribosome biogenesis inhibitor, BMH-21, demonstrated synergy in the PARPi-resistant cell lines, but not in the parental cells. Interestingly, HCC1395 cells, which had lower baseline nucleolar stress, showed greater nucleophosmin delocalization with combination treatment than MX1 cells, which had higher baseline nucleolar stress. All four cell lines demonstrated sustained DNA damage with the combination. We extended our investigation to 3 BRCA wild-type TNBC cell lines, BT549, Hs578T, and MDAMB231 and identified synergy in the context of intrinsic PARPi resistance. In MDAMB231 cells, combining olaparib with BMH-21 induced a senescence-like phenotype, increasing gH2AX-positive cells by up to 7.3-fold, senescence-associated B-galactosidase (SA-B-gal) staining by 5.6-fold, and p21 by 3.6-fold. These results were mirrored with a second ribosome biogenesis inhibitor, CX-5461. Finally, we identified distinct patterns of ribosomal pathway activity in a cohort of patients with treatment-resistant TNBC, and found correlations between ribosomal pathways with MYC, proliferation, DNA damage, and senescence. Together, these data identify ribosome biogenesis as a potential therapeutic vulnerability in PARPi-resistant TNBC and support its targeting in combination with PARPi, while demonstrating a broader for ribosome biogenesis in treatment-resistant TNBC.

Background Chemotherapy (CT) de-escalation strategies based on dual HER2 blockade with trastuzumab and pertuzumab (HP) have shown promising efficacy in HER2-positive (HER2+) early breast cancer (EBC), but biomarkers to guide patient selection are lacking. The Ataraxis Breast platform (ATX) uses artificial intelligence (AI) models integrating hematoxylin-eosin (H&E) whole-slide images and clinical variables to predict pathological complete response (pCR) and long-term outcomes. We evaluated ATX in the phase II PHERGain (NCT03161353) and PHERGain-2 (NCT04733118) trials. Methods The ATX NEO model was assessed for pCR prediction in PHERGain (n=306 evaluable patients) and PHERGain-2 (n=383 evaluable patients). The ATX RISK model was evaluated for prognosis in PHERGain (n=309 evaluable patients). Prespecified cutoffs classified patients into low-, medium-, and high-probability groups for pCR and low- or high-risk groups for recurrence. Associations with pCR were assessed using logistic regression. Prognostic performance was evaluated using Cox proportional hazards models, Kaplan-Meier estimates, and Harrell's C-index. Results Overall pCR rates were 40.2% in PHERGain and 60.3% in PHERGain-2. Continuous NEO scores were significantly associated with pCR in both PHERGain (odds ratio [OR], 1.28; 95% CI, 1.11-1.48; P<0.001) and PHERGain-2 (OR, 1.30; 95% CI, 1.13-1.52; P<0.001). Using prespecified cutoffs, pCR rates increased across low-, medium-, and high-probability groups (19.2%, 41.3%, and 48.3% in PHERGain; 29.5%, 61.6%, and 70.1% in PHERGain-2). In PHERGain, the RISK score was significantly associated with event-free survival (hazard ratio per 1-SD increase, 1.56; 95% CI, 1.17-2.08; P=0.002; C-index, 0.66). Five-year event-free survival was 93.9% in the low-risk group and 83.1% in the high-risk group. Conclusions NEO score was consistently associated with pCR across two independent HER2+ EBC trials, while RISK score provided prognostic information for long-term outcomes in PHERGain. Prespecified score categories identified clinically distinct response and risk groups. These findings support further evaluation of AI-based biomarkers to refine patient selection for CT de-escalation strategies in HER2+ EBC.

Background: Neoadjuvant chemotherapy (NACT) facilitates de-escalation of breast and axillary treatment in breast cancer, but pathological responses may differ between the primary tumour and axillary lymph nodes. Understanding differential response is crucial for de-escalation strategies. Methods: This single university hospital retrospective study analysed operable breast cancers (cT1-cT3, cN0-cN3) treated with NACT (January 2013-November 2020). Two-tailed Fishers exact test or the Chi-squared test (for 2x2 comparisons) analysed concordance between breast and axillary pathological responses; Cox proportional hazards regression ascertained predictors of distant recurrence and survival; and logistic regression ascertained predictors of complete axillary response. Results: Among 413 patients (cN0=229; cN+=184) with a median age of 51, pathological response concordance between the breast and axilla was 81% (both pCR, 22.2%; concurrent residual disease, 58.8%). The cN0 group had a significantly higher ypN0 rate in breast pCR versus non-pCR (97.1% vs 80.8%, p<0.001). cN+ had axillary pCR concordant with breast pCR, compared to only 16.5% with residual breast disease. Breast pCR was the most significant predictor of axillary pCR (OR=11.6, p<0.001). Axillary pCR was highest in ER-/HER2+(66.7%) and triple-negative(46.9%) subtypes. Residual axillary disease was independently associated with the worst breast cancer-specific (HR=7.13, p=0.006) and overall Survival (HR=3.32, p=0.029). Kaplan-Meier analyses showed a trend towards worse survival outcomes with axillary residual disease, even with a breast pCR. Conclusions: In this limited series, breast pCR predicts axillary pCR in cN0 and cN+, particularly in HER2-positives and triple-negatives, supporting axillary de-escalation strategies in selected patients stratified by careful assessment of disease at the end of NACT.

Backgroud Breast cancer is a leading cause of cancer-related mortality, and HR+/HER2-; is the predominant subtype. Molecular pathology, including PIK3CA and ESR1 mutation, informs prognosis and treatment selection. Circulating tumor DNA (ctDNA) offers a non-invasive approach for cancer monitoring, but its clinical utility is limited by tissue plasma discordance, reflecting heterogeneous ctDNA release. The cellular and spatial determinants of this release remain poorly understood, particularly in HR+/HER2-; subtype, where heterogeneity across subclones complicates liquid biopsy interpretation. Results To identify the cellular and spatial determinants of ctDNA release, we developed scMASTER, integrating single-cell transcriptomes and mutations, spatial transcriptomics and matched tumor and plasma DNA sequencing. In ten patients with non-metastatic HR+/HER2- breast cancer, eight recurrent malignant epithelial states showed distinct ctDNA release potential. Antigen-presentation, stress, mitosis and mesenchymal-like states showed high release. PIK3CA and ESR1 mutations were linked to distinct functional states and altered ctDNA detectability. Three spatial architectures, EMT-enriched regions, intraductal luminal progenitors and avascular hypoxic zones, showed high release. Tumor-microenvironment interactions were bidirectional: anti-tumoral immunity correlated with reduced release, whereas immunomodulatory components correlated with increased release. A stratification model based on these features identified high-risk, immunosuppressed patients with poor prognosis, validated across external cohorts. Conclusions Our study establishes a single-cell spatial framework for decoding ctDNA release heterogeneity, linking tumor states, somatic mutations, spatial architecture, and immune interactions to ctDNA release. These findings provide mechanistic insights into tissue-plasma discordance, offer a biological rationale for interpreting ctDNA dynamics, refine patient risk stratification and liquid biopsy-based monitoring in HR+/HER2-; breast cancer.

The FORESEE trial (NCT04450706) was a prospective study to evaluate the feasibility of integrating organoid-based drug testing with comprehensive genomic characterization to inform treatment selection in patients with HER2-negative metastatic breast cancer. The primary objective of the study was to determine the feasibility of providing personalized therapy recommendations using a combination of genomic vulnerability information with drug testing in patient-derived organoids (PDOs) in a clinically relevant time frame. Of the 15 patients enrolled, 10 cases had biopsies with adequate tumor content, and PDOs were successfully established in 4 of 10 cases. Drug profiling and genomic testing was completed in all established organoids, yielding an overall success rate of 40% in cases of biopsies with adequate tumor content. Drug sensitivity and genomic results were returned within 12 weeks and informed subsequent treatment selection in all evaluable cases. The primary endpoint - demonstrating that PDO-based drug screening combined with genomic characterization would identify clinically actionable outcomes in at least 46% of patients based on prior data - was not met. In conclusion, successful PDO establishment represents a limiting step in the implementation of FPO for metastatic breast cancer; however when PDO were successful, drug responses were always obtained and physicians chose to use the information in 100% of cases. These findings highlight the need for improved strategies optimizing use of patient biopsy material for drug testing in order to fully realize the clinical potential of FPO.

Background. Brain metastasis affects 15-30% of patients with breast cancer, yet brain-specific biology underlying central nervous system colonisation is poorly captured by available clinical measures. The choroid plexus, an MRI biomarker of neuroinflammation and a primary immune-cell gateway implicated in brain metastasis, has not been examined in this setting. Methods. In a real-world, cross-sectional study of 1,000 women with breast cancer (190 with brain metastasis), bilateral choroid plexus volumes on contrast-enhanced brain MRI were quantified using a deep-learning pipeline. Guided by the principle that hemispheric asymmetry indices are sensitive to focal pathology, this study derived from an exploratory bilateral volume comparison a parameter-free Choroid Plexus Asymmetry Index (CPAI = |L-R|/(L+R)). Multivariable logistic regression, propensity-score matching, laterality and grade-stratified analyses assessed robustness. Results. The results show that total choroid plexus volume does not differ between groups, whereas left and right volumes change asymmetrically and CPAI is elevated in patients with metastasis (median 0.088 vs 0.059; Cliff's delta = 0.20, 95% CI 0.10-0.29). CPAI is minimally correlated with 10 peripheral markers and with histological grade. The association is robust under multivariable adjustment (adjusted OR 1.58 per +1 SD, 95% CI 1.32-1.88) and propensity-score matching, with |CPAI| scaling with metastatic burden, independent of metastasis side. Conclusions. Choroid plexus morphological asymmetry on routine brain MRI is associated with breast cancer brain metastasis independently of peripheral inflammation, tumour grade and conventional markers.

The hormone receptor-positive luminal subtype accounts for approximately 70% of all diagnosed breast cancer cases, with endocrine regimens serving as the first-line therapy. However, 30% to 50% of luminal breast cancer patients acquire therapeutic resistance with five to ten years of treatment. Understanding the mechanisms of endocrine resistance and identifying new therapeutic targets remain urgent priorities. Here, we demonstrate that expression of the alpha subunit of prolyl 4-hydroxylase (P4HA1), a key collagen-modifying enzyme, is significantly upregulated in endocrine therapy-resistant luminal breast cancer cells compared to parental endocrine therapy-sensitive cells. Clinically, elevated P4HA1 expression correlates with shortened relapse-free survival in patients with luminal breast cancer. Genetically knocking down P4HA1 or pharmacologically inhibiting its activity successfully restores the sensitivity of endocrine-resistant luminal breast cancer cells to hormone therapy. Mechanistically, we reveal that combining P4HA1 inactivation with endocrine treatment dramatically enhances endoplasmic reticulum (ER) stress-related gene expression. Consistently, treating resistant cells with an exogenous ER stress inducer similarly enhances sensitivity to hormone therapy. Furthermore, we demonstrate that ER stress induced by P4HA1 inactivation is molecularly mediated by an accumulation of reactive oxygen species (ROS). Together, these findings uncover a novel, non-canonical role for P4HA1 as a critical mediator linking endocrine resistance to cellular stress adaptations, positioning P4HA1 as a promising therapeutic vulnerability in endocrine-resistant breast cancer. P4HA1 serves as a necessary role in maintenance resistant state, making it a viable target for combination therapies to overcome endocrine resistance.

The immunomodulatory effects of chemotherapy (chemoimmunomodulation; CIM) are clinically consequential and heterogeneous, yet no systematic framework exists for classifying the immunomodulatory trajectory a tumor follows in response to treatment (CIM trajectory). Here, we present the CIM Induction Classifier (CIMIC), an unsupervised clustering pipeline leveraging delta gene expression across 3,189 CIM-related genes to classify specimens chemoimmunomodulatory trajectory. Applied to two pre- and post-chemotherapy breast cancer (BC) datasets (NKI/SMC, N = 36; NEO, N = 19) and nine epirubicin-perturbed triple-negative BC (TNBC) cell lines, CIMIC identified two divergent CIM trajectories: a functional CIM (Fun-CIM) trajectory, broadly conserved across tumors and cell lines and characterized by induction of inflammatory cell death, antigen presentation, viral mimicry, and adaptive immune activation programs, and a dysfunctional CIM (Dys-CIM) trajectory, characterized by induction of proteostatic and metabolic stress-adaptation programs, reduced immune cell abundances and cytotoxic activity, and enrichment of aggressive BC subtypes. Using survival and longitudinal transcriptomic data in NKI/SMC (N = 20), treatment-induced increases in Fun-CIM-associated genes and ssGSEA scores were associated with reduced recurrence, whereas Dys-CIM-associated genes and scores were associated with increased recurrence. In multivariable analyses within independent chemotherapy-treated BC cohorts (METABRIC, N = 412; SCAN-B, N = 2,462), higher baseline Fun-CIM ssGSEA scores were associated with better outcomes, whereas higher baseline Dys-CIM ssGSEA scores were associated with worse outcomes. These findings establish CIM as a dynamic, trajectory-level process and position CIMIC as a framework for defining CIM trajectories and supporting future efforts to identify predictors, mechanisms, and therapeutic strategies that maximize beneficial CIM.

Bromodomain and extra-terminal (BET) proteins, BRD2, BRD3, BRD4, and BRDT, couple histone acetylation to transcription by recruiting elongation and transcription factor complexes to chromatin. Although BET proteins are promising therapeutic targets, the functions of individual family members remain incompletely understood. We identify BRD2 as a co-targetable vulnerability with PI3K/AKT inhibition in breast cancer. Pan-BET inhibition and BRD2 knockout synergized with PI3K pathway inhibitors in breast cancer cell lines, patient-derived organoids, and in vivo models. BRD2 knockout impaired proliferation of triple-negative breast cancer cells and upregulated signaling and stress-response pathways, including the DNA damage response. Mechanistically, BRD2 is phosphorylated at Ser37 by the mitogen- and stress-activated kinases MSK and RSK, and Ser37 phosphorylation is required for chromatin binding and reader function. Finally, mechanistic digital twin modeling identified BETi-PI3Ki regimens that maintained efficacy while reducing drug exposure. Together, these findings identify BRD2 as a phosphorylation-dependent, co-targetable vulnerability in PI3K-inhibited breast cancer.

Systemic immunosuppression promotes metastatic progression and immunotherapy resistance, yet reliable biomarkers and noninvasive tools for longitudinal monitoring remain limited. Building on our finding that CXCL1+ neutrophil abundance in major organs inversely correlates with breast cancer-induced systemic immunosuppression, we developed an imaging-based immunosuppression gauge using CXCR2-expressing cells that mimic CXCL1+ neutrophil trafficking. Following intravenous administration, the biodistribution of engineered CXCR2-overexpressing mesenchymal stem cells or healthy donor neutrophils was imaged at 24 h, with greater organ accumulation indicating lower systemic immunosuppression. These living, distributed biosensors integrate chemokine signals across multiple organs and convert host immune status into an imageable biodistribution pattern. The gauge distinguished tumor aggressiveness at early disease stages, predicted metastatic risk before overt metastatic outgrowth, identified chemoimmunotherapy responders, and informed treatment selection through longitudinal immune monitoring. Mechanistically, nonaggressive tumors failed to induce substantial systemic immunosuppression and were effectively controlled by surgery alone, whereas aggressive tumors continued to drive immunosuppression after resection. Neoadjuvant chemoimmunotherapy produced superior outcomes to adjuvant treatment by intervening before profound immunosuppression developed and more effectively restoring antitumor immunity. Across cancer models, long-term survivors consistently showed resolution of systemic immunosuppression and restoration of immune activity to healthy-host levels. Thus, imaging systemic immunosuppression provides an early, longitudinal indicator of metastatic risk, therapeutic response, and treatment efficacy.

Background: This study compared functional and cognitive trajectories in older women treated for early breast cancer with matched women without cancer. Methods: Data were derived from two Dutch cohorts: the CLIMB study (women aged 75 years and older with operable breast cancer) and the ISCOPE study (community-dwelling women aged 75 years and older without cancer). Breast cancer patients were matched 1:2 to controls on age and baseline functional or cognitive status. Functional status was assessed using the Groningen Activity Restriction Scale (GARS), and cognitive function using the Mini-Mental State Examination (MMSE). Longitudinal changes over 12 months were analyzed using both unadjusted and confounder-adjusted linear mixed models. Results: 168 breast cancer patients and 336 matched breast cancer-free controls were included with a mean age of 80 years. Most breast cancer patients had stage 0-I or II disease and received surgery and/or radiotherapy; 48% received adjuvant endocrine therapy, chemotherapy was rare (<1%). At baseline, both cohorts were comparable in age and functional or cognitive status, although there was a higher comorbidity burden in the control cohort. No significant differences in functional or cognitive decline were observed between the cohorts over 12 months. Conclusions: In older women, early breast cancer and its treatment did not lead to accelerated decline in functional status or cognitive function within the first year compared to matched older women without cancer. These findings suggest that, for relatively fit older patients, breast cancer treatment may not accelerate functional decline in the short term.

HER2-directed therapies are expanding across solid tumors, but ERBB2 amplification incompletely captures HER2 expression and pan-tumor IHC lacks standardization. We developed ERBB2 mRNA, bulk HER2 protein and RNA-signature screening benchmarked against IHC/FISH. Screening identified HER2-enriched populations beyond amplification in a pan-tumor discovery cohort of 1,331 tumor biopsies and validated RNA-based screening in an external cohort of 3,898 tumor biopsies. All six objective responses among 51 treated patients in the discovery cohort occurred in tumors positive by ERBB2 mRNA and the combined RNA-signature. In the external dataset (n=102), ERBB2 mRNA positivity was associated with longer time on treatment (hazard ratio 0.42, 95% confidence interval 0.27-0.64) and overall survival (0.41, 0.25-0.65), with concordant associations for the combined RNA signature. Spatial proteomics comprising 2,721 tiles across 88 samples captured HER2 hetero-geneity and identified HER2-enriched profiles below bulk thresholds. These findings support prospective evaluation of RNA and proteomic screening for treatment selection.

PurposeMen with pathogenic BRCA1 and BRCA2 variants (BRCA+) have an elevated lifetime risk of male breast cancer (MBC) yet data regarding mammography in this population remain limited. MethodsWe performed a retrospective cohort study of BRCA+ assigned male at birth individuals (males) at Penn (1/1/2008-5/1/2024) and the Veterans Administration (VA, 10/1/2002-1/1/2026) for mammography uptake. Mammography results and MBC characteristics were compared between BRCA+ and BRCA-males. ResultsAmong 810 BRCA+ males, 19% had a documented mammogram for screening or symptoms. Among 562 BRCA+ males age-eligible for mammogram without prior MBC, most (63%) had documentation of a mammography-related discussion and 16% completed mammogram, of whom 25% were BRCA1+ and 75% were BRCA2+. Among mammograms obtained for screening of 97 BRCA+ males, there were few BI-RADS 4/5 (N=1, 1%) and no MBC was detected. Symptom-indicated mammograms in 59 BRCA+ compared to 228 BRCA-males yielded BI-RADS 4/5 findings in 35% versus 25%, p<0.0001, and MBC diagnoses in 29% versus 21%, p=0.219. The positive predictive value (PPV) of BI-RADS 4/5 lesions was similar in BRCA+ vs BRCA-males (71% vs 74% and 100% vs 93%, respectively). Among 22 BRCA+ and 57 BRCA-MBC, 55% and 42% were node positive and 82% and 86% were ER+Her2-, respectively. ConclusionScreening mammography utilization among BRCA+ males was low despite elevated hereditary risk. Regardless of BRCA status, nearly all MBC were diagnosed based on symptoms, and a high proportion of MBC were diagnosed at advanced stages. Our findings identify a critical need for both improved identification of males at high risk for breast cancer and improved screening practices of high-risk men.

Stromal cell composition has been proposed as a potential biomarker in ductal carcinoma in situ (DCIS) for assessing the risk of subsequent recurrence or progression to invasive breast cancer (IBC). However, the characteristics of the tumor microenvironment within DCIS associated with these outcomes remain poorly understood. Here, we perform spatial transcriptomic analyses of 49 primary DCIS specimens from patients with no recurrence, DCIS recurrence, or recurrence as IBC. Cell mapping reveals spatially organized stromal cell gradients within DCIS, with enrichment of TREM2+ macrophages and myofibroblastic cancer-associated fibroblasts (myCAFs) in tumor-proximal niches. Notably, the abundance of TREM2+ macrophages near tumor nests is associated with subsequent recurrence as IBC. Moreover, ligand-receptor pair analysis identifies GRN--SORT1, SPP1--CD44, and LGALS9--CD44 interactions as spatially plausible signaling interactions between TREM2+ macrophages and epithelial cells. Finally, these findings are validated at the protein level by multiplex immunostaining of serial sections. This study characterizes the spatial landscape of the DCIS tumor microenvironment associated with subsequent recurrence, providing a basis for developing biomarkers of disease progression and identifying potential therapeutic targets.

Long-term treatment sequelae shape health and quality of life for years after breast cancer, yet why some women develop them and others recover remains unclear. Here we follow 16 women through chemotherapy and for two years afterwards, with patient-reported symptoms, clinical chemistries, plasma proteomics, metabolomics, and gut microbiome profiles collected across eight visits from a pre-treatment baseline. Sequelae differ in their timing, with some resolving as chemotherapy ends, whereas fatigue, memory problems, and gas bloating can persist, and weight gain and joint pain can appear only afterwards. Weight gain over the second year scales with the cumulative duration of endocrine therapy and is steepest in premenopausal women. The women who remain fatigued at two years are distinguished by a second surge in fatigue scores beginning around 12 months post-chemotherapy rather than by a failure to recover, as well as by elevated plasma INHBB and depleted RAB37. INHBB is also elevated in UK Biobank participants reporting chronic, moderate, or severe fatigue, measured on the same platform. In the gut microbiome, Faecalibacterium prausnitzii, a butyrate producer, is depleted in the fatigued group at 24 months post-chemotherapy. Our analysis revealed that post-treatment sequelae follow distinct trajectories, each with its own onset. Markers that track those trajectories point to time windows in which intervention could begin before symptoms become established.

Breast cancer progression is driven by dynamic changes in epithelial plasticity, membrane organization, and intracellular signaling, yet the effects of sustained low-dose chemotherapy on these processes remain poorly understood. Here, we investigated the impact of prolonged low-dose doxorubicin on membrane remodeling, epithelial phenotype, membrane-associated Ras lipid-anchor localization, and autophagy in mesenchymal-like MDA-MB-231 breast cancer cells. Low-dose doxorubicin significantly increased Caveolin-1 expression and enhanced E-cadherin protein levels, accompanied by a transition toward a more compact epithelial-like morphology with increased cell-cell contacts. Live-cell imaging demonstrated a significant reduction in the membrane-to-cytoplasm fluorescence ratio of the lipid-anchored GFP-tH probe, indicating redistribution from the plasma membrane to the cytoplasm following treatment. Analysis of autophagy-related proteins revealed decreased LC3-I together with increased LC3-II, ATG5, and p62 expression, consistent with autophagosome accumulation and impaired autophagic flux. Collectively, our findings demonstrate that low-dose doxorubicin promotes extensive remodeling of plasma membrane organization, epithelial plasticity, membrane-associated lipid-anchor localization, and autophagy. This integrated response reveals previously unrecognized links between membrane architecture, Ras membrane association, and autophagy during phenotypic reprogramming of breast cancer cells, providing mechanistic insight into cellular adaptations elicited by sub-cytotoxic doxorubicin exposure.

Objectives: To develop and validate pixel data analysis (PDA) for reconstructing pixel-level shear-wave velocity (SWV) from saved Holder-Optimized Elastography (HOE) elastograms and to determine whether whole-field subcutaneous heterogeneity provides a quantitative signature of lymphatic obstruction compared with visual high-velocity-area (HVA) counting and sparse manual region-of-interest (ROI) sampling. Materials and Methods: In this cross-sectional study, 110 women after breast cancer surgery underwent lymphoscintigraphy and HOE, a pressure-minimized acquisition framework that preserves conventionally captured SWV information while additionally revealing spatial abnormalities attenuated by handheld acquisition. Reconstruction validation used 200 paired ROIs from 49 PACS-retrieved images spanning nearly the full displayed SWV range; reproducibility was assessed across 96 matched anatomical sites from 6 participants undergoing independently reacquired HOE examinations. PDA, visual HVA counting, and manual ROI sampling were evaluated on the same HOE-acquired elastograms in task-specific common complete-case cohorts. Results: PDA reconstructed machine-reported SWV with near-zero error (mean difference, +0.0009 m/s; mean absolute error, 0.0075 m/s; 95% limits of agreement, -0.0202 to +0.0221 m/s). For subcutaneous variance, interobserver/intraobserver ICCs were 0.718/0.799 for PDA and 0.161/0.560 for manual ROI sampling. In the primary no-versus-partial comparison (n = 93), forearm-pooled PDA subcutaneous variance ratio yielded the highest observed AUC (0.859; 95% CI, 0.772 - 0.947), compared with 0.820 for visual HVA counting and 0.769 for manual ROI sampling. PDA's subcutaneous variance ratio remained a leading feature across all three comparisons (AUC, 0.859 - 0.878), including partial-versus-total grading, where all three frameworks showed high discrimination. Conclusions: PDA accurately reconstructs pixel-level SWV from saved HOE elastograms and enables reproducible whole-field quantification of superficial SWE heterogeneity. Subcutaneous variance ratio was the leading quantitative PDA feature across lymphatic-obstruction comparisons and was particularly informative in partial obstruction. The same approach also enables retrospective quantitative reanalysis of compatible archived elastograms.