TROPION-Breast01: Datopotamab deruxtecan vs chemotherapy in pre-treated inoperable or metastatic HR+/HER2- breast cancer.

Improving the prognosis for patients with metastatic HR+/HER2- breast cancer remains an unmet need. Patients with tumors that have progressed on endocrine therapy and/or are not eligible for endocrine therapy had limited treatment options beyond chemotherapy. Antibody-drug conjugates are a novel and promising treatment class in this setting. Datopotamab deruxtecan (Dato-DXd) consists of a TROP2-directed humanized IgG1 monoclonal antibody attached via a serum-stable cleavable linker to a topoisomerase I inhibitor payload. TROPION-Breast01 is an ongoing phase III study that is evaluating the efficacy and safety of Dato-DXd compared with investigator's choice of standard-of-care chemotherapy in patients with inoperable or metastatic HR+/HER2- breast cancer who have received one or two prior lines of systemic chemotherapy in the inoperable or metastatic setting. Clinical Trial Registration: NCT05104866 (ClinicalTrials.gov).

Antibody-drug conjugates are a type of drug with two parts: an antibody that directs the drug to the cancer cells and a cancer-cell killing toxic payload. By binding to cancer cells before releasing the payload, treatment is directed to the site of action so there are fewer side effects in the rest of the body. Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugates made up of datopotamab (antibody) and DXd (payload) which are joined together via a stable linker. Datopotamab binds to a protein found on cancer cells called TROP2; it then goes inside and releases the DXd payload to kill the tumor cells. DXd may leak out to surrounding cancer cells and kill those as well. The TROPION-Breast01 study is comparing Dato-DXd with standard-of-care chemotherapy. Around 700 patients will take part, who have: Tumors that cannot be surgically removed. Tumors that are hormone receptor-positive and do not have HER2 overexpression. Had one or two lines of previous chemotherapy (after the tumor could not be surgically removed, or had spread). Had tumor growth despite hormonal therapy or are ineligible for hormonal therapy. Patients who meet the entry criteria will be randomly assigned to a treatment group in equal numbers to either Dato-DXd or an appropriate chemotherapy, out of four options chosen by the treating doctor. At the end of the study, researchers will look at whether the patients who receive Dato-DXd live longer without their breast cancer getting worse, compared with patients who receive chemotherapy. This study is also looking at how the treatment affects patients' quality of life.

Determinants of activity and efficacy of anti-PD1/PD-L1 therapy in patients with advanced solid tumors recruited in a clinical trials unit: a longitudinal prospective biomarker-based study.

Immune-checkpoint inhibitors (ICI) have revolutionized the therapeutic landscape of cancer. However, optimal patient selection is still an unmet need. One-hundred-forty-six patients with metastatic cancer candidates to ICI at the Hospital Clinic of Barcelona Clinical Trials Unit were prospectively recruited in this observational study. Blood samples were collected at different timepoints, baseline LIPI score calculated and pre-ICI archived tissues retrieved to evaluate PD-L1, tumor-infiltrating lymphocytes (TILs) and PD1 mRNA levels. Tumor assessments were centrally reviewed by RECIST 1.1 criteria. Associations with overall response rates (ORR), durable clinical benefit (DCB), progression-free survival (PFS) and overall survival (OS) were performed with univariable/multivariable logistic and Cox regressions, where appropriate. At a median follow-up of 26.9 months, median PFS and OS were 2.7 and 12.9 months. Response rates were 17.8% with duration of response (DOR) of 4.4 months. LIPI score was independently associated with PFS (p = 0.025) and OS (p < 0.001). Immunotherapy-naïve status was independently associated with better PFS (p = 0.005). Time-to-best response (TTBR) and ORR (p < 0.001 both) were associated with better OS at univariate analysis. PFS and DOR were moderately correlated with OS (p < 0.001 both). A PD-L1 10% cut-off detected worse/best responders in terms of ORR (univariate p = 0.011, multivariate p = 0.028) and DCB (univariate p = 0.043). PD1 mRNA levels were strikingly associated to complete responses (p = 0.021). To resume, in our prospective observational pan-cancer study, baseline LIPI score, immunotherapy-naïve status, cancer type and RT before starting ICI were the most relevant clinical factors independently correlated with immunotherapy outcomes. Longer TTBR seemed to associate with better survival, while PD1 mRNA and PD-L1 protein levels might be tumor-agnostic predictive factors of response to ICI and should be furtherly explored.

A multivariable prognostic score to guide systemic therapy in early-stage HER2-positive breast cancer: a retrospective study with an external evaluation.

BACKGROUND: In early-stage HER2-positive breast cancer, escalation or de-escalation of systemic therapy is a controversial topic. As an aid to treatment decisions, we aimed to develop a prognostic assay that integrates multiple data types for predicting survival outcome in patients with newly diagnosed HER2-positive breast cancer. METHODS: We derived a combined prognostic model using retrospective clinical-pathological data on stromal tumour-infiltrating lymphocytes, PAM50 subtypes, and expression of 55 genes obtained from patients who participated in the Short-HER phase 3 trial. The trial enrolled patients with newly diagnosed, node-positive, HER2-positive breast cancer or, if node negative, with at least one risk factor (ie, tumour size >2 cm, histological grade 3, lymphovascular invasion, Ki67 >20%, age ≤35 years, or hormone receptor negativity), and randomly assigned them to adjuvant anthracycline plus taxane-based combinations with either 9 weeks or 1 year of trastuzumab. Trastuzumab was administered intravenously every 3 weeks (8 mg/kg loading dose at first cycle, and 6 mg/kg thereafter) for 18 doses or weekly (4 mg/kg loading dose in the first week, and 2 mg/kg thereafter) for 9 weeks, starting concomitantly with the first taxane dose. Median follow-up was 91·4 months (IQR 75·1-105·6). The primary objective of our study was to derive and evaluate a combined prognostic score associated with distant metastasis-free survival (the time between randomisation and distant recurrence or death before recurrence), an exploratory endpoint in Short-HER. Patient samples in the training dataset were split into a training set (n=290) and a testing set (n=145), balancing for event and treatment group. The training set was further stratified into 100 iterations of Monte-Carlo cross validation (MCCV). Cox proportional hazard models were fit to MCCV training samples using Elastic-Net. A maximum of 92 features were assessed. The final prognostic model was evaluated in an independent combined dataset of 267 patients with early-stage HER2-positive breast cancer treated with different neoadjuvant and adjuvant anti-HER2-based combinations and from four other studies (PAMELA, CHER-LOB, Hospital Clinic, and Padova) with disease-free survival outcome data. FINDINGS: From Short-HER, data from 435 (35%) of 1254 patients for tumour size (T1 vs rest), nodal status (N0 vs rest), number of tumour-infiltrating lymphocytes (continuous variable), subtype (HER2-enriched and basal-like vs rest), and 13 genes composed the final model (named HER2DX). HER2DX was significantly associated with distant metastasis-free survival as a continuous variable (p<0·0001). HER2DX median score for quartiles 1-2 was identified as the cutoff to identify low-risk patients; and the score that distinguished quartile 3 from quartile 4 was the cutoff to distinguish medium-risk and high-risk populations. The 5-year distant metastasis-free survival of the low-risk, medium-risk, and high-risk populations were 98·1% (95% CI 96·3-99·9), 88·9% (83·2-95·0), and 73·9% (66·0-82·7), respectively (low-risk vs high-risk hazard ratio [HR] 0·04, 95% CI 0·0-0·1, p<0·0001). In the evaluation cohort, HER2DX was significantly associated with disease-free survival as a continuous variable (HR 2·77, 95% CI 1·4-5·6, p=0·0040) and as group categories (low-risk vs high-risk HR 0·27, 0·1-0·7, p=0·005). 5-year disease-free survival in the HER2DX low-risk group was 93·5% (89·0-98·3%) and in the high-risk group was 81·1% (71·5-92·1). INTERPRETATION: The HER2DX combined prognostic score identifies patients with early-stage, HER2-positive breast cancer who might be candidates for escalated or de-escalated systemic treatment. Future clinical validation of HER2DX seems warranted to establish its use in different scenarios, especially in the neoadjuvant setting. FUNDING: Instituto Salud Carlos III, Save the Mama, Pas a Pas, Fundación Científica, Asociación Española Contra el Cáncer, Fundación SEOM, National Institutes of Health, Agenzia Italiana del Farmaco, International Agency for Research on Cancer, and the Veneto Institute of Oncology, and Italian Association for Cancer Research.

Frequency and spectrum of PIK3CA somatic mutations in breast cancer.

PURPOSE: The therascreen PIK3CA mutation assay and the alpha-specific PI3K inhibitor alpelisib are FDA-approved for identifying and treating patients with advanced PIK3CA-mutated (PIK3CAmut) breast cancer (BC). However, it is currently unknown to what extend this assay detects most PIK3CA mutations in BC. This information is critical as patients and clinicians are using this and other genomic assays to indicate alpelisib. METHODS: Data from 6338 patients with BC was explored across 10 publicly available studies. The primary objective was to evaluate the proportion and distribution of PIK3CA mutations in BC. Secondary objectives were (1) to evaluate in silico the spectrum of PIK3CA mutations in BC that would be captured by the therascreen panel; (2) to evaluate the proportion and distribution of PIK3CA mutations in hormone receptor-positive/HER2-negative (HR+/HER2-), HER2+, and triple-negative BC (TNBC); and (3) to explore the identification of PIK3CA mutations in a cohort of 48 HR+/HER2- advanced BC patients by the Guardant B360 circulating tumor DNA (ctDNA) assay. RESULTS: Patients with PIK3CAmut tumors represented 35.7% (2261/6338). Five PIK3CA mutations comprised 73% of all PIK3CA mutations: H1047R (35%), E545K (17%), E542K (11%), N345K (6%), and H1047L (4%). Therascreen gene list would capture 72% of all PIK3CA mutations and 80% of patients with a known PIK3CAmut BC. Among patients with double PIK3CAmut tumors (12% of all PIK3CAmut), the therascreen panel would capture 78% as harboring 1 single PIK3CA mutation, 17% as PIK3CAmut undetected, and 5% as PIK3CA double-mut. PIK3CA mutation rates were lower in TNBC (16%) compared to HR+/HER2 (42%) and HER2+ (31%) BC; however, the distribution of the 4 main PIK3CA mutations across subtypes was similar. Finally, 28% of PIK3CA mutations identified in ctDNA in 48 patients with advanced HR+/HER2- BC were not part of the therascreen panel. CONCLUSION: PIK3CA mutations in BC are heterogenous and ~ 20% of patients with a known PIK3CA mutation, and 95% with a known double PIK3CAmut tumor, would not be captured by the therascreen panel. Finally, the clinical utility of PIK3CA mutations not present in the therascreen companion diagnostic assay or identified by other sequencing-based assays needs further investigation.

Oral metronomic vinorelbine combined with endocrine therapy in hormone receptor-positive HER2-negative breast cancer: SOLTI-1501 VENTANA window of opportunity trial.

BACKGROUND: The biological effect of oral metronomic vinorelbine (mVNB) alone or in combination with endocrine therapy in patients with hormone receptor-positive (HR+)/HER2-negative breast cancer has been scarcely addressed. METHODS: Postmenopausal women with untreated stage I-III HR+/HER2-negative breast cancer were randomized (1:1:1) to receive 3 weeks of letrozole (LTZ) 2.5 mg/day, oral mVNB 50 mg 3 days/week, or the combination. The primary objective was to evaluate, within PAM50 Luminal A/B disease, if the anti-proliferative effect of LTZ+mVNB was superior to monotherapy. An anti-proliferative effect was defined as the mean relative decrease of the PAM50 11-gene proliferation score in combination arm vs. both monotherapy arms. Secondary objectives included the evaluation of a comprehensive panel of breast cancer-related genes and safety. An unplanned analysis of stromal tumor-infiltrating lymphocytes (sTILs) was also performed. PAM50 analyses were performed using the nCounter®-based Breast Cancer 360™ gene panel, which includes 752 genes and 32 signatures. RESULTS: Sixty-one patients were randomized, and 54 paired samples (89%) were analyzed. The main patient characteristics were mean age of 67, mean tumor size of 1.7 cm, mean Ki67 of 14.3%, stage I (55.7%), and grades 1-2 (90%). Most baseline samples were PAM50 Luminal A (74.1%) or B (22.2%). The anti-proliferative effect of 3 weeks of LTZ+mVNB (- 73.2%) was superior to both monotherapy arms combined (- 49.9%; p = 0.001) and mVNB (- 19.1%; p < 0.001). The anti-proliferative effect of LTZ+mVNB (- 73.2%) was numerically higher compared to LTZ (- 65.7%) but did not reach statistical significance (p = 0.328). LTZ+mVNB induced high expression of immune-related genes and gene signatures, including CD8 T cell signature and PDL1 gene and low expression of ER-regulated genes (e.g., progesterone receptor) and cell cycle-related and DNA repair genes. In tumors with ≤ 10% sTILs at baseline, a statistically significant increase in sTILs was observed following LTZ (paired analysis p = 0.049) and LTZ+mVNB (p = 0.012). Grade 3 adverse events occurred in 3.4% of the cases. CONCLUSIONS: Short-term mVNB is well-tolerated and presents anti-proliferative activity alone and in combination with LTZ. The high expression of immune-related biological processes and sTILs observed with the combination opens the possibility of studying this combination with immunotherapy. Further investigation comparing these biological results with other metronomic schedules or drug combinations is warranted. TRIAL REGISTRATION: NCT02802748 , registered 16 June 2016.

Everolimus plus Exemestane for Hormone Receptor-Positive Advanced Breast Cancer: A PAM50 Intrinsic Subtype Analysis of BOLERO-2.

BACKGROUND: The prognostic and predictive value of the two nonluminal (human epidermal growth factor receptor 2 [HER2]-enriched and basal-like) subtypes within advanced hormone receptor-positive (HR+) breast cancer is currently unknown. MATERIALS AND METHODS: This study retrospectively analyzed 261 tumors (80.7% primary; 19.3% metastatic) from the BOLERO-2 study; BOLERO-2 randomized 724 patients with advanced HR+/HER2-negative breast cancer to everolimus plus exemestane or placebo plus exemestane. Tumors were classified using a PAM50 subtype predictor. Multivariable Cox regression analyses tested the independent prognostic significance of PAM50, and associations between PAM50 subtypes and treatment upon progression-free survival (PFS) were evaluated. RESULTS: Subtype distribution was 46.7% luminal A (n = 122), 21.5% HER2-enriched (n = 56), 15.7% luminal B (n = 41), 14.2% normal-like (n = 37), and 1.9% basal-like (n = 5); HER2-enriched subtypes were more common in metastatic versus primary tumors (32.0% vs. 18.7%; p = .038). Median PFS differences between luminal and nonluminal (6.7 vs. 5.2 months; adjusted hazard ratio, 0.66; 95% confidence interval [CI], 0.47-0.94; p = .020) and HER2-enriched and non-HER2-enriched subtypes (5.2 vs. 6.2 months; adjusted hazard ratio, 1.53; 95% CI, 1.07-2.19; p = .019) were significant. Everolimus plus exemestane significantly improved median PFS versus placebo plus exemestane among patients with HER2-enriched tumors (5.8 vs. 4.1 months; adjusted hazard ratio, 0.49; 95% CI, 0.26-0.90; p = .034); however, the association between HER2-enriched tumors and everolimus benefit was nonsignificant (p = .433). CONCLUSION: The HER2-enriched subtype was identified in a substantial proportion of advanced HR+/HER2-negative breast tumors, and was a consistent biomarker of poor prognosis. Tailored therapies are therefore needed for HER2-enriched tumors in the advanced HR+/HER2-negative breast cancer setting. IMPLICATIONS FOR PRACTICE: Using 261 tumor samples from the BOLERO-2 phase III clinical trial, this study shows that a substantial proportion (20%-30%) of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancers do not have a luminal A or B gene expression profile. This group of patients with nonluminal disease has a poor survival outcome regardless of the addition of everolimus to exemestane. This is the second study that confirms the prognostic value of this biomarker. Overall, these findings indicate a necessity to design novel clinical trials targeting nonluminal disease within HR+/HER2-negative breast cancer.

Response and survival of breast cancer intrinsic subtypes following multi-agent neoadjuvant chemotherapy.

BACKGROUND: Predicting treatment benefit and/or outcome before any therapeutic intervention has taken place would be clinically very useful. Herein, we evaluate the ability of the intrinsic subtypes and the risk of relapse score at diagnosis to predict survival and response following neoadjuvant chemotherapy. In addition, we evaluated the ability of the Claudin-low and 7-TNBCtype classifications to predict response within triple-negative breast cancer (TNBC). METHODS: Gene expression and clinical-pathological data were evaluated in a combined dataset of 957 breast cancer patients, including 350 with TNBC, treated with sequential anthracycline and anti-microtubule-based neoadjuvant regimens. Intrinsic subtype, risk of relapse score based on subtype and proliferation (ROR-P), the Claudin-low subtype and the 7-TNBCtype subtype classification were evaluated. Logistic regression models for pathological complete response (pCR) and Cox models for distant relapse-free survival (DRFS) were used. RESULTS: Basal-like, Luminal A, Luminal B, and HER2-enriched subtypes represented 32.7%, 30.6%, 18.2%, and 10.3% of cases, respectively. Intrinsic subtype was independently associated with pCR in all patients, in hormone receptor-positive/HER2-negative disease, in HER2-positive disease, and in TNBC. The pCR rate of Basal-like disease was >35% across all clinical cohorts. Neither the Claudin-low nor the 7-TNBCtype subtype classifications predicted pCR within TNBCs after accounting for intrinsic subtype. Finally, intrinsic subtype and ROR-P provided independent prognostic information beyond clinicopathological variables and type of pathological response. A 5-year DRFS of 97.5% (92.8-100.0%) was observed in these neoadjuvant-treated and clinically node-negative patients predicted to be low risk by ROR-P (i.e. 57.4% of Luminal A tumors with clinically node-negative disease). CONCLUSIONS: Intrinsic subtyping at diagnosis provides prognostic and predictive information for patients receiving neoadjuvant chemotherapy. Although we could not exclude a survival benefit of neoadjuvant chemotherapy in patients with early breast cancer with clinically node-negative and ROR-low disease at diagnosis, the absolute benefit of cytotoxic therapy in this group might be rather small (if any).

The risk of toxicities from trastuzumab, alone or in combination, in an elderly breast cancer population.

BACKGROUND: Breast cancer in the elderly is associated with high recurrence and death rates, due mostly to undertreatment. Human epidermal growth factor receptor type 2 (HER2) overexpression is infrequent in older patients. Trastuzumab-based chemotherapy is often withheld from elderly patients because of its cardiotoxicity. PATIENTS AND METHODS: Medical records of consecutive HER2-positive breast cancer patients aged ≥70 years old treated between 2005 and 2010 in the participating centers were retrospectively reviewed. All patients underwent multidimensional geriatric assessment (MGA). RESULTS: Among 59 patients identified, 51 patients were evaluable (median age 76 years). The rate of any adverse event was 20% (10/51). The most relevant cardiac adverse event consisted of symptomatic congestive heart failure (CHF; n = 1, 2%) followed by asymptomatic decreases of left ventricular ejection fraction (LVEF; n = 6, 12%). Other toxicities included moderate hypersensitivity reactions during trastuzumab infusions (n = 3, 6%). Hypertension, obesity, prior anthracyclines exposure and concurrent chemotherapy were associated with a higher incidence of toxic events. Previous radiotherapy, concurrent endocrine therapy and different trastuzumab-based regimens did not seem to influence toxicity. CONCLUSIONS: Our data suggest that trastuzumab has a good safety profile in nonfrail women aged 70 years and older. These favorable findings may be related to a limited number of anthracycline pretreatments, patient selection and a close cardiologic monitoring.

Current status of fertility preservation in a Spanish tertiary public hospital: multidisciplinary approach and experience in over 1500 patients.

PURPOSE: Currently, 15% of gynaecological and 9% of haematological malignancies are diagnosed before the age of 40. The increased survival rates of cancer patients who are candidates for gonadotoxic treatments, the delay in childbearing to older ages, and the optimization of in vitro fertilisation techniques have all contributed to an increased interest in fertility preservation (FP) treatments. This study reviews the experience of the Fertility Preservation Programme (FPP) of a tertiary public hospital with a multidisciplinary approach. METHODS: This retrospective study included all the available (FP) treatments, performed in patients of childbearing age between 2006 and 2022. RESULTS: 1556 patients were referred to the FPP: 332 oocyte vitrification cycles, 115 ovarian cortex cryopreservation with 11 orthotopic autotransplantations, 175 gonadotropin-releasing hormone (GnRH) agonist treatments, 109 fertility-sparing treatments for gynaecological cancer, and 576 sperm cryopreservation were performed. Malignancy was the main indication for FP (the main indications being breast cancer in women and haematological malignancies in men), although non-oncological pathologies, such as endometriosis and autoimmune diseases, have increased in recent years. Currently, the most widely used FP technique is oocyte vitrification, the increase of which has been associated with a decrease in the use of cortex CP and GnRH agonists. CONCLUSIONS: The increase in FP treatment reflects the implementation of reproductive counselling in oncology programmes. A multidisciplinary approach in a tertiary public hospital allows individualised FP treatment for each patient. In recent years, there has been a change in trend with the introduction of new indications for FP and a change in techniques due to their optimisation.

A 14-gene B-cell immune signature in early-stage triple-negative breast cancer (TNBC): a pooled analysis of seven studies.

BACKGROUND: Early-stage triple-negative breast cancer (TNBC) displays clinical and biological diversity. From a biological standpoint, immune infiltration plays a crucial role in TNBC prognosis. Currently, there is a lack of genomic tools aiding in treatment decisions for TNBC. This study aims to assess the effectiveness of a B-cell/immunoglobulin signature (IGG) alone, or in combination with tumor burden, in predicting prognosis and treatment response in patients with TNBC. METHODS: Genomic and clinical data were retrieved from 7 cohorts: SCAN-B (N = 874), BrighTNess (n = 482), CALGB-40603 (n = 389), METABRIC (n = 267), TCGA (n = 118), GSE58812 (n = 107), GSE21653 (n = 67). IGG and a risk score integrating IGG with tumor/nodal staging (IGG-Clin) were assessed for event-free survival (EFS) and overall survival (OS) in each cohort. Random effects model was used to derive pooled effect sizes. Association of IGG with pathological complete response (pCR) was assessed in CALGB-40603 and BrighTNess. Immune significance of IGG was estimated through CIBERSORTx and EcoTyper. FINDINGS: IGG was associated with improved EFS (pooled HR = 0.77, [95% CI = 0.70-0.85], I2 = 18%) and OS (pooled HR = 0.79, [0.73-0.85], I2 = 0%) across cohorts, and was predictive of pCR in CALGB-40603 (OR 1.25, [1.10-1.50]) and BrighTNess (OR 1.57 [1.25-1.98]). IGG-Clin was predictive of recurrence (pooled HR = 2.11, [1.75-2.55], I2 = 0%) and death (pooled HR = 1.99, 95% [0.84-4.73], I2 = 79%) across cohorts. IGG was associated with adaptive immune response at CIBERSORTx and EcoTyper analysis. INTERPRETATION: IGG is linked to improved prognosis and pCR in early-stage TNBC. The integration of IGG alongside tumor and nodal staging holds promise as an approach to identify patients benefitting from intensified or de-intensified treatments. FUNDING: This study received funding from: Associació Beca Marta Santamaria, European Union's Horizon 2020 research and innovation and Marie Sklodowska-Curie Actions programs, Fundación FERO, Fundación CRIS contra el cáncer, Agència de Gestó d'Ajuts Universitaris i de Recerca, Instituto de Salud Carlos III, Fundación Contigo, Asociación Cáncer de Mama Metastásico IV, Breast Cancer Research Foundation, RESCUER, Fundación científica AECC and FSEOM.

Molecular characterization of basal-like and non-basal-like triple-negative breast cancer.

Triple-negative (TN) and basal-like (BL) breast cancer definitions have been used interchangeably to identify breast cancers that lack expression of the hormone receptors and overexpression and/or amplification of HER2. However, both classifications show substantial discordance rates when compared to each other. Here, we molecularly characterize TN tumors and BL tumors, comparing and contrasting the results in terms of common patterns and distinct patterns for each. In total, when testing 412 TN and 473 BL tumors, 21.4% and 31.5% were identified as non-BL and non-TN, respectively. TN tumors identified as luminal or HER2-enriched (HER2E) showed undistinguishable overall gene expression profiles when compared versus luminal or HER2E tumors that were not TN. Similar findings were observed within BL tumors regardless of their TN status, which suggests that molecular subtype is preserved regardless of individual marker results. Interestingly, most TN tumors identified as HER2E showed low HER2 expression and lacked HER2 amplification, despite the similar overall gene expression profiles to HER2E tumors that were clinically HER2-positive. Lastly, additional genomic classifications were examined within TN and BL cancers, most of which were highly concordant with tumor intrinsic subtype. These results suggest that future clinical trials focused on TN disease should consider stratifying patients based upon BL versus non-BL gene expression profiles, which appears to be the main biological difference seen in patients with TN breast cancer.

Characterization of cell lines derived from breast cancers and normal mammary tissues for the study of the intrinsic molecular subtypes.

Five molecular subtypes (luminal A, luminal B, HER2-enriched, basal-like, and claudin-low) with clinical implications exist in breast cancer. Here, we evaluated the molecular and phenotypic relationships of (1) a large in vitro panel of human breast cancer cell lines (BCCLs), human mammary fibroblasts (HMFs), and human mammary epithelial cells (HMECs); (2) in vivo breast tumors; (3) normal breast cell subpopulations; (4) human embryonic stem cells (hESCs); and (5) bone marrow-derived mesenchymal stem cells (hMSC). First, by integrating genomic data of 337 breast tumor samples with 93 cell lines we were able to identify all the intrinsic tumor subtypes in the cell lines, except for luminal A. Secondly, we observed that the cell lines recapitulate the differentiation hierarchy detected in the normal mammary gland, with claudin-low BCCLs and HMFs cells showing a stromal phenotype, HMECs showing a mammary stem cell/bipotent progenitor phenotype, basal-like cells showing a luminal progenitor phenotype, and luminal B cell lines showing a mature luminal phenotype. Thirdly, we identified basal-like and highly migratory claudin-low subpopulations of cells within a subset of triple-negative BCCLs (SUM149PT, HCC1143, and HCC38). Interestingly, both subpopulations within SUM149PT were enriched for tumor-initiating cells, but the basal-like subpopulation grew tumors faster than the claudin-low subpopulation. Finally, claudin-low BCCLs resembled the phenotype of hMSCs, whereas hESCs cells showed an epithelial phenotype without basal or luminal differentiation. The results presented here help to improve our understanding of the wide range of breast cancer cell line models through the appropriate pairing of cell lines with relevant in vivo tumor and normal cell counterparts.

HER2DX ERBB2 mRNA expression in advanced HER2-positive breast cancer treated with T-DM1.

In advanced HER2-positive (HER2+) breast cancer, the new antibody-drug conjugate trastuzumab deruxtecan is more effective compared with trastuzumab emtansine (T-DM1). However, trastuzumab deruxtecan can have considerable toxicities, and the right treatment sequence is unknown. Biomarkers to guide the use of anti-HER2 therapies beyond HER2 status are needed. Here, we evaluated if preestablished levels of ERBB2 mRNA expression according to the HER2DX standardized assay are associated with response and survival following T-DM1. In ERBB2 low, medium, and high groups, the overall response rate was 0%, 29%, and 56%, respectively (P < .001). ERBB2 mRNA was statistically significantly associated with better progression-free survival (P = .002) and overall survival (OS; P = .02). These findings were independent of HER2 immunohistochemistry (IHC) levels, hormone receptor, age, brain metastasis, and line of therapy. The HER2DX risk score (P = .04) and immunoglobulin signature (P = .04) were statistically significantly associated with overall survival since diagnosis. HER2DX provides prognostic and predictive information following T-DM1 in advanced HER2+ breast cancer.

Circulating tumor DNA reveals complex biological features with clinical relevance in metastatic breast cancer.

Liquid biopsy has proven valuable in identifying individual genetic alterations; however, the ability of plasma ctDNA to capture complex tumor phenotypes with clinical value is unknown. To address this question, we have performed 0.5X shallow whole-genome sequencing in plasma from 459 patients with metastatic breast cancer, including 245 patients treated with endocrine therapy and a CDK4/6 inhibitor (ET + CDK4/6i) from 2 independent cohorts. We demonstrate that machine learning multi-gene signatures, obtained from ctDNA, identify complex biological features, including measures of tumor proliferation and estrogen receptor signaling, similar to what is accomplished using direct tumor tissue DNA or RNA profiling. More importantly, 4 DNA-based subtypes, and a ctDNA-based genomic signature tracking retinoblastoma loss-of-heterozygosity, are significantly associated with poor response and survival outcome following ET + CDK4/6i, independently of plasma tumor fraction. Our approach opens opportunities for the discovery of additional multi-feature genomic predictors coming from ctDNA in breast cancer and other cancer-types.

Clinical significance of circulating interleukin-23 as a prognostic factor in breast cancer patients.

Little is known about specific IL-23 alterations associated with breast cancer and the data available are still controversial. Therefore, the evaluation of changes in serum IL-23 levels may add further information on the role of this cytokine in breast cancer patients. The aim of this study was to evaluate prospectively the prognostic importance of circulating IL-23 in patients with untreated breast cancer, respect to healthy controls, and the association with clinico-pathological variables. The study involved 50 women diagnosed with stages I-IV breast cancer and 38 healthy controls. Of the 50 breast cancer patients, 37 women were recruited prior to their initial adjuvant chemotherapy and 13 prior to receive first line chemotherapy for metastatic disease. Adjuvant chemotherapy patients were at least in their 4th week post-surgery. IL-23 serum concentrations were measured by a quantitative enzyme immunoassay technique. We found a statistically significant higher systemic cytokine value in women with cancer in comparison with the control group (14.52±11.39 pg/ml vs. 6.35±4.63 pg/ml, P<0.0001). Patients with shorter overall survival presented higher IL-23 values, suggesting a negative prognostic correlation. There was no significant differences in IL-23 levels among patients according to the biomolecular characteristics, the different subtypes and the presence of metastatic disease. This work investigated, for the first time, the role of IL-23 in breast cancer patients showing a significant increase respect the control group. However, further validations are needed in larger studies to better investigate the implications of IL-23 increase in these patients.

Gene expression profiles of breast cancer metastasis according to organ site.

In advanced breast cancer, biomarker identification and patient selection using a metastatic tumor biopsy is becoming more necessary. However, the biology of metastasis according to the organ site is largely unknown. Here, we evaluated the expression of 771 genes in 184 metastatic samples across 11 organs, including liver, lung, brain, and bone, and made the following observations. First, all PAM50 molecular intrinsic subtypes were represented across organs and within immunohistochemistry-based groups. Second, HER2-low disease was identified across all organ sites, including bone, and HER2 expression significantly correlated with ERBB2 expression. Third, the majority of expression variation was explained by intrinsic subtype and not organ of metastasis. Fourth, subtypes and individual subtype-related genes/signatures were significantly associated with overall survival. Fifth, we identified 74 genes whose expression was organ-specific and subtype-independent. Finally, immune profiles were found more expressed in lung compared to brain or liver metastasis. Our results suggest that relevant tumor biology can be captured in metastatic tissues across a variety of organ sites; however, unique biological features according to organ site were also identified and future studies should explore their implications in diagnostic and therapeutic interventions.

Stratifying triple-negative breast cancer: which definition(s) to use?

Triple-negative breast cancers (TNBC) have increased rates of pathologic complete response following neoadjuvant chemotherapy, yet have poorer prognosis compared with non-TNBC. Known as the triple-negative paradox, this highlights the need to dissect the biologic and clinical heterogeneity within TNBC. In the present issue, Keam and colleagues suggest two subgroups of TNBC exist based on the proliferation-related marker Ki-67, each with differential response and prognosis following neoadjuvant chemotherapy. To place results into context, we review several definitions available under the TNBC umbrella that may stratify TNBC into clinically relevant subgroups.

Phosphatidylinositol 3-kinase pathway activation in breast cancer brain metastases.

INTRODUCTION: Activation status of the phosphatidylinositol 3-kinase (PI3K) pathway in breast cancer brain metastases (BCBMs) is largely unknown. We examined expression of phospho(p)-AKT, p-S6, and phosphatase and tensin homologue (PTEN) in BCBMs and their implications for overall survival (OS) and survival after BCBMs. Secondary analyses included PI3K pathway activation status and associations with time to distant recurrence (TTDR) and time to BCBMs. Similar analyses were also conducted among the subset of patients with triple-negative BCBMs. METHODS: p-AKT, p-S6, and PTEN expression was assessed with immunohistochemistry in 52 BCBMs and 12 matched primary BCs. Subtypes were defined as hormone receptor (HR)+/HER2-, HER2+, and triple-negative (TNBC). Survival analyses were performed by using a Cox model, and survival curves were estimated with the Kaplan-Meier method. RESULTS: Expression of p-AKT and p-S6 and lack of PTEN (PTEN-) was observed in 75%, 69%, and 25% of BCBMs. Concordance between primary BCs and matched BCBMs was 67% for p-AKT, 58% for p-S6, and 83% for PTEN. PTEN- was more common in TNBC compared with HR+/HER2- and HER2+. Expression of p-AKT, p-S6, and PTEN- was not associated with OS or survival after BCBMs (all, P > 0.06). Interestingly, among all patients, PTEN- correlated with shorter time to distant and brain recurrence. Among patients with TNBC, PTEN- in BCBMs was associated with poorer overall survival. CONCLUSIONS: The PI3K pathway is active in most BCBMs regardless of subtype. Inhibition of this pathway represents a promising therapeutic strategy for patients with BCBMs, a group of patients with poor prognosis and limited systemic therapeutic options. Although expression of the PI3K pathway did not correlate with OS and survival after BCBM, PTEN- association with time to recurrence and OS (among patients with TNBC) is worthy of further study.

Clinical, pathological, and PAM50 gene expression features of HER2-low breast cancer.

Novel antibody-drug conjugates against HER2 are showing high activity in HER2-negative breast cancer (BC) with low HER2 expression (i.e., 1+ or 2+ and lack of ERBB2 amplification). However, the clinical and molecular features of HER2-low BC are yet to be elucidated. Here, we collected retrospective clinicopathological and PAM50 data from 3,689 patients with HER2-negative disease and made the following observations. First, the proportion of HER2-low was higher in HR-positive disease (65.4%) than triple-negative BC (TNBC, 36.6%). Second, within HR-positive disease, ERBB2 and luminal-related genes were more expressed in HER2-low than HER2 0. In contrast, no gene was found differentially expressed in TNBC according to HER2 expression. Third, within HER2-low, ERBB2 levels were higher in HR-positive disease than TNBC. Fourth, HER2-low was not associated with overall survival in HR-positive disease and TNBC. Finally, the reproducibility of HER2-low among pathologists was suboptimal. This study emphasizes the large biological heterogeneity of HER2-low BC, and the need to implement reproducible and sensitive assays to measure low HER2 expression.