ER-positive Disease Research Articles

Clinical utility of molecular imaging in newly diagnosed metastatic breast cancer.

1019 Background: Optimizing patient outcome prediction in metastatic breast cancer (MBC) can potentially reduce patients’ and healthcare burden. Molecular imaging to visualize early metabolic change, baseline whole-body human epidermal growth factor receptor-2 (HER2) and estrogen receptor (ER) expression might achieve this. In the prospective multicenter IMPACT study, we evaluated the clinical utility of molecular imaging to improve standard diagnostics in patients with newly diagnosed MBC of all subtypes. Methods: Patients underwent extensive workup, including baseline metastasis biopsy, [18F]FDG-PET, [89Zr]trastuzumab-PET (HER2-PET), [18F]FES-PET, and early [18F]FDG-PET after 2 weeks. Treatment was based on HER2 or ER subtype determined in biopsy (immunohistochemistry, IHC; standard-of-care) or PET findings (HER2- and [18F]FES-PET; investigational) in case of negative biopsy but positive HER2 and/or [18F]FES-PET scan. Clinical utility of molecular imaging was defined as the capacity to identify poor patient outcome, measured as progressive disease (PD) on CT at 8 weeks, progression-free survival (PFS), and overall survival (OS). Results: Two hundred patients were included. Progression on early [18F]FDG-PET was related to poor outcome in all subtypes (median PFS 4.1 versus 19.4 months, OS 19.4 versus 45.0 months). Early [18F]FDG-PET correctly predicted non-PD on 8 week CT (specificity 90.5%, negative predictive value 94.1%), but sensitivity and positive predictive value for PD was low (50 and 37.5%, respectively). However, early [18F]FDG-PET related better to long-term outcome than CT: patients with non-PD on 8 week CT, but with progression on early [18F]FDG-PET, had a median PFS and OS of 9.5 and 22.3 months respectively, compared to 19.4 and 50.1 months without [18F]FDG-PET progression (PFS HR 1.76 (95%CI 1.0 – 2.9), OS HR 1.93 (1.0 – 3.5)). HER2 or ER subtype was discrepant between biopsy and PET in 52 out of 200 (26%) patients, yielding investigational PET-based treatment options in 41 (21%) patients. In patients with HER2-positive biopsy IHC disease who received standard HER2-targeting treatment, median PFS with positive- versus negative HER2-PET was 23.2 and 4.5 months, respectively. In patients with biopsy IHC HER2-negative disease but positive HER2-PET, median PFS was with investigational HER2-targeted treatment 11.4 months, without 7.4 months. The pattern was similar in ER-positive disease, although less pronounced for biopsy- and PET-based subtypes. Conclusions: This study supports the clinical utility of molecular imaging with [18F]FDG-PET, HER2-PET, and [18F]FES-PET, to improve standard diagnostics for outcome and subtype assessment in patients with newly diagnosed MBC. Clinical trial information: NCT01957332 .

Incidence and survival of primary metastatic breast cancer in Denmark; implication of breast cancer screening, classification, and staging practice.

Primary metastatic breast cancer (pMBC) accounts for 5-10% of annual breast cancers with a median survival of 3-4 years, varying among subtypes. In Denmark, the incidence of breast cancer increased until 2010, followed by a stabilisation. Several factors influencing pMBC incidence and survival, including screening prevalence, staging methods, and classification standards, remain pivotal but inadequately documented. This retrospective observational study involving pMBC patients diagnosed between 2000 and 2020 encompassed all Danish oncology departments. Data from the Danish Breast Cancer Group database and the National Patient Register included diagnosis specifics, demographics, treatment, and follow-up. Between 2000 and 2020, 3,272 patients were diagnosed with pMBC, a rise from 355 patients in 2000-2004 to 1,323 patients in 2015-2020. The increase was particularly observed in patients aged 70 years or older. Changes in tumour subtypes were observed, notably with a rise in human epidermal growth factor receptor 2 (HER2)-positive cases but a steady distribution of estrogen receptor (ER) status. Diagnostic practices changed over the two decades, with 6% evaluated with PET/CT (positron emission tomography-computed tomography) or CT (computed tomography) with a bone evaluation in 2000-2004 and 65% in 2015-2020. Overall survival (OS) improved from 23 months in 2000-2004 to 33 months in 2015-2020. In patients with ER-positive and HER2-positive disease, the multivariable model showed improved survival by year of diagnosis, and further, patients with ER-negative/HER2-negative disease fared worse the first 2 years after diagnosis. Our study delineates changes in the treatment and survival of pMBC over two decades. Stage migration, screening introduction, and changes in registration practice, however, prevent a valid assessment of a possible causal relationship.

Abstract PO4-02-05: Elevated tumor to aorta ratio of Hounsfield units and late recurrence in patients with estrogen receptor positive breast cancer

Abstract Background) More than half of the recurrent disease in breast cancer will happen more than 5 years after initial diagnosis in breast cancer, especially in patients with ER positive disease. Higher proportions of late recurrence lead to escalated treatment and/or or extended treatment for high risk patients. However, it is unclear what characteristics make whom as high risk patients. This study aimed to assess initial tumor vascularity as a prognostic marker for late recurrence. Methods) Female patients with estrogen receptor positive breast cancer who were diagnosed breast cancer between 2003 and 2018 and disease-free at 5 years after primary breast cancer at Wonju Severance Hospital, Korea, were included. Clinocopathological characteristics were collected. Hounsfield units(HU) on contrast-enhanced computed tomography(CT) was used as a marker indicating tumor vascularity. Tumor to aortic arch ratio(TAR) of HU on contrast enhanced CT was applied to enhance objectivity of measurement. Patients were categorized according to the cut-off values retrieved from the receiver operating characteristic curve. Kaplan-Meier curves were generated to compare recurrence-free survival (RFS) and overall survival (OS). Hazard ratio(HR) with confidence interval(CI) was derived with Cox’s proportional hazard model to analyze univariate and multivariate risk factors. Results) The final cohort included 451 patients with a mean age of 56.21 ± 11.2 (22-83) years. Two third of patients had estrogen receptor positive disease and a quarter of patients had HER2 overexpressed disease. Initial TAR was 0.345 ± 0.108 (range, 0.062 - 1.114). Patients with recurrence free survival(RFS)-related events had significantly higher TAR than patients who did not(0.39 ± 0.097 vs. 0.34 ± 0.108, p=0.012). Patients with overall survival(OS)-related events also had higher TAR than patients who did not(0.408 ± 0.096 vs. 0.342 ± 0.107, p=0.002). Cutoff value of 0.408 was driven from area under the receiver operating characteristic curve. Patients with TAR higher than 0.408 showed significantly worse RFS(p=0.001) and OS(p< 0.001) than patients who had TAR equal or lower than 0.408. Hazard ratio(HR) of TAR in late recurrence was 6.17 (CI, 4.89 – 9.23, p=0.003), suggesting it is an independent factor. Other independent factors were age (HR, 1.502; CI, 10.14 – 10.91; p=0.006), tumor size (HR, 1.268; CI, 1.071 – 1.502; p=0.006), and metastatic nodal disease (HR, 2.770; CI, 1.176 – 6.526; p=0.020). Conclusion) TAR of primary tumor was significantly related with patients RFS and OS. Patients with high TAR larger than 0.408 showed worse RFS and OS than patients who did not. According to the Cox proportional hazard model, TAR was an independent factor along with age, tumor size, and metastatic nodal disease, suggesting late recurrence may rather be influenced by clinical factor Citation Format: Airi Han, Hyang Suk Choi, Seok Hahn, In-jeoung Cho, Seung Taek Lim, Jong-In Lee. Elevated tumor to aorta ratio of Hounsfield units and late recurrence in patients with estrogen receptor positive breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-02-05.

Abstract PS06-09: Fragmentomic analysis of a circulating tumor DNA targeted cancer gene panel discriminates ER status in metastatic breast cancer liquid biopsies

Abstract Background: Circulating tumor DNA (ctDNA) isolated from the peripheral blood of patients with cancer is now routinely used in the clinic to detect tumor somatic mutations, with multiple ctDNA-targeted sequencing panels commercially available for Food and Drug Administration (FDA)-approved biomarker indications to guide targeted therapy options. More recently, it has been appreciated that ctDNA fragmentation patterns are influenced by the chromatin structure of the cell of origin, with greater diversity in fragment size in areas with open chromatin and less diversity in fragment size in areas with closed chromatin. In consequence, multiple studies have found that ctDNA fragmentation patterns can be used to accurately infer epigenomic and transcriptomic phenotypes from their tumor cells of origin. However, these analyses have previously relied on whole-genome sequencing (WGS), and it is not feasible to identify FDA-approved biomarker indications in a cost-effective manner with WGS. Methods: Peripheral blood was collected from a cohort of 90 patients with metastatic HER2-negative breast cancer (ER-positive n=71, ER-negative n=19). Cell-free DNA was extracted from plasma and sequenced using a custom 822 gene pan-cancer targeted sequencing panel (IDT). Shannon entropy of first coding exon fragment sizes (E1SE) was used to quantify fragmentation patterns. Higher diversity of fragment sizes, leading to a higher E1SE, are expected in ctDNA derived from areas of the genome with more open chromatin. A machine learning model utilizing the E1SE metric across all genes in the targeted panel was developed to distinguish between ER-positive and ER-negative disease. Results: Training cross-validated accuracy of the machine learning model was 87.8% with AUC of 0.91 to distinguish between ER-positive and ER-negative disease, despite a median ctDNA fraction of only 0.02. E1SE metrics for ESR1 and CCND1 were significantly higher in ER-positive than ER-negative samples, while E1SE metrics for EGFR, c-Kit and members of the MAP kinase family were significantly higher in ER-negative than ER-positive samples, consistent with anticipated differences in gene expression between ER-positive and ER-negative triple negative breast cancers. In contrast, HER2 E1SE was similar between groups, as expected in this clinically HER2-negative cohort. Conclusions: We have shown for the first time that sequencing from standard targeted ctDNA panels can be utilized to infer phenotypic information through analysis of ctDNA fragmentation patterns in patients with metastatic breast cancer. This expands the depth of potential biologic data that can be extracted from targeted ctDNA sequencing panels in addition to DNA mutation status in a cost-effective manner. In the future, this approach can be exploited to expand ctDNA-based biomarker development beyond DNA mutation status. Citation Format: Kyle Helzer, Jamie Sperger, Yue Shi, Viridiana Carreno, Hannah Krause, Katherine Kaufmann, Leilani Mora-Rodriguez, Matthew Bootsma, Mark Burkard, Ruth O'Regan, Kari Wisinski, Joshua Lang, Shuang (George) Zhao, Malinda West, Marina Sharifi. Fragmentomic analysis of a circulating tumor DNA targeted cancer gene panel discriminates ER status in metastatic breast cancer liquid biopsies [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS06-09.

Abstract PO1-16-01: Clinicopathological and global transcriptional complexity of estrogen receptor low positive breast cancers in a contemporary Swedish prospective population-based cohort

Abstract Background: Estrogen receptor (ER) expression is currently the most consequential biomarker for prognostic and therapeutic decision making in clinical management of early breast cancer. Endocrine therapy (ET) is an important part of standard of care in most cases with ER-positive disease, and an effective therapy for patients with endocrine-responsive tumors, decreasing the risk of recurrence and improving the rate of survival. Unfortunately, ET comes with frequently bothersome side-effects and tend to decrease quality of life. The threshold to define ER positivity as a marker of endocrine responsiveness is non-uniform between international and local guidelines. Among ER low positive tumors (ERlow ,1-10% expression) endocrine responsiveness is uncertain. Swedish national guidelines recommend a cut-off of ≥10% for ER positivity and ET prescriptions, thus patients with ERlow tumors are often exempted from adjuvant ET. This study explores the clinicopathological characteristics, global transcriptional complexity and clinical outcome of ERlow tumors to better understand their biology and response to therapy. Methods: 9138 patients diagnosed with early breast cancer between 2010 – 2021 in Sweden with available clinicopathological data and RNA sequencing data were included. Patients were classified according to ER expression: ERneg (< 1%; n=897), ERlow (1-10%, n=158) and ERhigh ( >10%, n=8083). Adjuvant ET was provided to 3.6%, 16.8% and 91.5% of patients with ERneg, ERlow, and ERhigh tumors, respectively. Clinicopathological characteristics, overall survival (OS) and global transcriptional profiles of ERlow tumors were compared with ERneg and ERhigh tumors, respectively. Results: Generally, ERlow and ERneg tumor pathological characteristics were more similar to each other but were significantly distinct compared to ERhigh tumors. However, among patients with HER2-negative disease only, significant differences related to tumor biology persisted between ERlow compared with ERneg tumors; ERlow was enriched with tumors displaying a lobular histology, NHG grades 1&2, PgRlow/high expression, low proliferation and Luminal & HER2-enriched molecular subtypes (p< 0.05 for all comparisons). Moreover, multivariable survival analyses revealed that the risk of dying was significantly lower for patients with ERlow tumors compared to patients with ERneg (p=0.005) or ERhigh tumors (p=0.011) in this cohort. The distribution of clinicopathological characteristics and overall survival between ERlow compared with ERneg or ERhigh tumors were similar among patients with HER2-positive tumors only. Global transcriptional comparisons identified only 42 genes to be differentially expressed between ERlow vs ERneg tumors (FDR< 0.05); but gene set enrichment analyses failed to identify any significantly enriched cancer-related processes/pathways within the queried databases. Conclusions: Identification of optimal therapies for all subsets of breast cancer is necessary in the pursuit of personalized medicine. These results confirm that ERneg and ERlow tumors are pathologically and transcriptionally distinct from ERhigh tumors. Although subtle differences exists in the underlying biology of ERlow compared to ERneg tumors, similar therapeutic management excluding ET for patients with ERlow and ERneg disease is recommended in the Swedish context. Omission of adjuvant ET did not seem to compromise overall survival for ERlow relative to ERneg or ERhigh tumors, urging the need for prospective studies investigating the true benefit of ET for ERlow tumors. Our results also raise reasonable clinical thoughts on the benefits of new treatment strategies such as cyclin-dependent kinase 4/6 inhibitors, immunotherapy and antibody-drug conjugates for patients with ERlow expressing tumors. Citation Format: Siker Kimbung, Srinivas Veerla, Anna Ehinger, Johan Vallon-Christersson, Martin Malmberg, Niklas Loman. Clinicopathological and global transcriptional complexity of estrogen receptor low positive breast cancers in a contemporary Swedish prospective population-based cohort [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-16-01.

Abstract PO3-18-08: Rational therapeutic combination of Bromodomain and Extra-Terminal domain (BET) inhibitor and Fibroblast Growth Factor Receptor (FGFR) inhibitor for treatment of invasive lobular carcinoma

Abstract Background: Invasive lobular carcinoma (ILC) is the second most pervasive subtype after invasive ductal carcinoma (IDC), accounting for approximately 10-15% of all breast cancers. It is characterized by loss of E-cadherin expression and non-adherent tumor cells that invade the stroma in a “single-file” pattern. Women with ILC are typically diagnosed at an older age and later stage with ER-positive disease. ILC is more likely to exhibit late recurrence and metastasize to the gastrointestinal tract and urogenital tract compared with IDC. It is routinely treated with anti-endocrine therapy and chemotherapy, however, while not entirely chemo-refractory, displays a poor response to chemotherapy compared with IDC. As such, options for recurrent disease are limited and there is an urgent need to develop tailored therapy for ILC, especially for those patients that recur. The family of bromodomain and extra-terminal domain (BET) proteins, comprising BRD2/3/4/T, are epigenetic readers that bind to acetylated lysine residues on histones and recruit transcription factors to drive the expression of oncogenes. Previously. we discovered that BRD3 is a marker of poor prognosis in ILC and there is emerging evidence that BET inhibitors (iBET) are effective in diverse types of breast cancer. Here, we investigated the therapeutic potential of iBET in ILC, alone and in combination with FGFR inhibitors. Methods: IC50s for a panel of iBET using two typical ILC cell lines MDA-MB-134VI (MM134) and SUM44PE (SUM44) were determined. RNA-sequencing and Genexplain analysis was applied to reveal transcriptional networks, master regulators and potential resistance mechanisms. BRD3 and FGFR3 were knocked down using siRNA to evaluate their function in ILC cell lines. Furthermore, we utilized ILC cell-derived xenograft (CDX) models in SCID-beige mice established by mammary intraductal (MIND) implantation to evaluate the therapeutic potency of iBET alone or in combination with fibroblast growth factor receptor (FGFR) inhibitor in vivo. Results: We demonstrated that iBET significantly inhibited ILC cell growth in both 2D and 3D culture, with the greatest potency demonstrated by JQ1 and Mivebresib (ABBV-075). RNA-sequencing revealed dysregulated pathways in cell cycle division, DNA damage, apoptosis and MAPK signaling following iBET treatment. Reverse engineering of transcriptional profiles using Genexplain revealed that FGFR3 is a significantly upregulated master regulator (MTR) among 142 MTRs across both cell lines and both iBETs. Upregulation of FGFR3 after iBET treatment was verified at the protein level by Western blotting. We also show that BRD3 and FGFR3 knockdown significantly inhibited cell growth, which supports the key role both play in ILC progression. Further, we analyzed the iBET therapeutic effect when combined with the FGFR inhibitor, erdafitinib, as a strategy to overcome potential resistance due to FGFR upregulation post iBET treatment. This revealed that the combination of iBET and erdafitinib could inhibit ILC cell growth more effectively compared to using either agent alone. Furthermore, our in vivo study showed that JQ1 could inhibit tumor growth in a SUM44-MIND model and alleviate metastasis to peritoneum, bone and ovary compared with the vehicle group. Moreover, we also assessed the combination of mivebresib and erdafitinib in vivo. This revealed that iBET and an FGFR inhibitor work synergistically to decrease tumour burden and metastatic potential in both MM134-MIND and SUM44-MIND models. Conclusion: Our results provide evidence that iBET, either alone or in combination with erdafitinib, is remarkably effective at inhibiting ILC growth, both in vitro and in vivo and represents a rational therapeutic strategy for recurrent ILC patients in the future. Citation Format: Binbin Gao, Elspeth Ward, Anna Blümel, Emer Conroy, Rachel Moore, Grainne Cremin, Rachel Bleach, Kathryn Haley, Tríona Ní Chonghaíle, Andreas Lindner, Jochen Prehn, Yi Zhang, Idalia Cruz, Leena Hilakivi-Clarke, Georgios Sflomos, Cathrin Brisken, William Gallagher, Darran O'Connor. Rational therapeutic combination of Bromodomain and Extra-Terminal domain (BET) inhibitor and Fibroblast Growth Factor Receptor (FGFR) inhibitor for treatment of invasive lobular carcinoma [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-18-08.

Abstract PO5-16-02: Investigating survivin as a novel target for immunotherapy in diverse breast cancer patients

Abstract Background: The BIRC5 gene encodes survivin, a tumor-specific antigen associated with aggressive tumor features, Black race and poor prognosis in breast cancer (BC). Recent studies have shown that anti-survivin vaccines stimulate a strong anti-tumor immune response in multiple tumor types. However, the relationship between BIRC5/survivin and immune response in BC is poorly understood, particularly among diverse patients. In this analysis, we sought to investigate the relationship between BIRC5/survivin and the BC immune microenvironment across clinical tumor features and RNA-based risk scores for genomic instability. Methods: We leveraged the Carolina Breast Cancer Study (CBCS), a large population-based study that oversampled young (≤50 years) and Black women with invasive BC. NanoString mRNA expression profiling was used to evaluate breast tumor expression for 10 major immune cell types, adaptive and innate immune response, TP53 and homologous recombination deficiency (HRD) pathways, and BIRC5/survivin from 1952 BC patients, including 1,030 (53%) Black and 922 (47%) non-Black women from the CBCS, with additional comparison in The Cancer genome Atlas (TCGA) (n=1,095 breast tumors). BIRC5 was evaluated both as a continuous and categorical variable, using the third expression quartile as a cut point for BIRC5-high, with the lower three quartiles categorized as BIRC5-low. We used generalized linear models to estimate beta values and adjusted p-values as the measure of association between BIRC5 status and immune-related expression in strata defined by estrogen receptor (ER) status, tumor stage, TP53 and HRD status. All analyses were adjusted for multiple comparisons with the Benjamini-Hochberg procedure. Results: In an analysis of continuous BIRC5 expression and global classes of immune response, BIRC5 mRNA expression was highest among tumors with an adaptive-enriched immune class (p< 0.001) in both CBCS and TCGA. However, when investigating immune gene expression according to BIRC5 status (i.e., BIRC5-high relative to BIRC5-low), multivariate differential expression analysis revealed significantly decreased immune cell-related expression scores among BIRC5-high tumors relative to BIRC5-low, and this relationship persisted in analysis stratified on stage (I/II vs III/IV), ER status, TP53 and HRD status. Across all strata, the strongest relationship between BIRC5-high and the immune microenvironment was observed for adaptive immune response (Beta: -0.14; p=0.005), with decreased immune gene expression related to B cells (Beta: -0.16; p=0.01), T cells (Beta: -0.14; p=0.007), Cytotoxic cells (Beta: -0.14; p=0.005), and PD-L1 (Beta: -0.15; p=0.005), relative to BIRC5-low. Conclusion: High BIRC5/survivin expression is associated with decreased immune-related gene expression in both ER-positive and ER-negative disease, and across all tumor stages. Anti-survivin therapies may be beneficial for boosting immune response in breast tumors with low immunogenicity, offering promise for BC subtypes previously ineligible for immunotherapy. Citation Format: Alina Hamilton, Qichen Wang, Sarah Soppe, Melissa Troester, Yara Abdou. Investigating survivin as a novel target for immunotherapy in diverse breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-16-02.

Abstract PO5-17-04: Tolerability of pertuzumab in older adults with HER2 positive breast cancer: A single institution experience

Abstract Background: Tumor HER2 over-expression occurs in 10 to 15% of older adults with breast cancer (BC). Combination HER2-directed therapy (pertuzumab and trastuzumab) with chemotherapy (CT) is the standard treatment for early and advanced HER2-positive bc. However, a study of more than 1,300 Medicare beneficiaries showed that about half of patients (pts) aged 65 or older with stage I to III HER2 positive bc did not receive trastuzumab-based therapy. This is likely due to concern for tolerability as older women remain underrepresented in clinical trials of breast cancer making it difficult to extrapolate tolerability of these agents in these patients. In the Neosphere and TRYPHAENA studies, the mean age of pts were 49.8 and 50.6 years, respectively. We examined the real-world tolerability of pertuzumab in combination with trastuzumab and systemic ct in women over the age of 65 with HER2 positive bc. Methods: An IRB approved retrospective review of medical records was conducted evaluating pts over the age of 65 with early or advanced HER2 positive bc treated at The Ohio State University Comprehensive Cancer center from January 1, 2015 to May,1 2020. Descriptive statistics (means, standard deviations, medians and ranges for continuous variables and frequencies and percents for categorical variables) were used to summarize disease and patient characteristics for pts enrolled in this study and treated with pertuzumab. The total number of planned and completed cycles of treatment as well as the number of treatment delays and dose reductions were also summarized using frequencies and percentages. The same descriptive statistics were used to summarize the number of grade II or IV toxicities and pathologic complete response (pCR) in the neoadjuvant setting. Results: A total of 71 pts met inclusion criteria. Mean age was 76 years (SD 4.1). Of these pts, 62 had stage I-III disease and 9 had metastatic disease. Additionally, 68% (48/71) had estrogen positive (ER) disease whereas 32% (23/71) had ER negative disease. Neoadjuvant systemic therapy was provided to 81% (50/62) of non-metastatic pts and 19% (12/62) received adjuvant therapy. The median number of completed neoadjuvant cycles (ct plus trastuzumab and pertuzumab) was 5.4 (SD 1.5). Among those who received pertuzumab with systemic ct in the neoadjuvant setting, 46% (23/50) of pts achieved a pCR (56% for ER negative disease and 41% for ER positive disease) The median number of completed adjuvant cycles (ct plus trastuzumab and pertuzumab) was 4.9 (SD 2.0). Pts with stage I to III disease completed a mean of 8.6 (SD 5.0) targeted therapy cycles (pertuzumab/trastuzumab). Pts with metastatic disease had a median of 5.7 (SD 1.0) cycles of ct plus trastuzumab and pertuzumab and received a mean of 34.4 (SD 36.0) cycles of maintenance pertuzumab. Treatment delay by 7 or more days occurred in 11% (8/71) of pts whereas 25% (18/71) of pts discontinued pertuzumab early. Pertuzumab termination occurred due to toxicity in 44% (8/18), metastasis in 11% (2/18), and other causes in 44% (8/18) of cases. For toxicities, 2% (1/51) of patients reported grade 3 pain, 25% (2/8) reported grade 3 fatigue, and 12% reported grade 4 diarrhea (1/8) (Table 1). Conclusions: Our study showed that pertuzumab was well tolerated in older pts with bc in the real-world setting. However, 25 % of pts still discontinued pertuzumab early which illustrates the importance of identifying pts who are at higher risk for toxicities prior to starting treatment. Table 1 Reported adverse events in patients age 65 and older receiving pertuzumab Citation Format: Nicole Williams, Austin Warmbier, Dureti Doto, Marilly Palettas, Julie Stephens, Dionisia Quiroga, Kai Johnson, Ashley Pariser, Mathew Cherian, Sagar Sardesai, Daniel Stover, Margaret Gatti-Mays, Robert Wesolowski, Bhuvana Ramaswamy. Tolerability of pertuzumab in older adults with HER2 positive breast cancer: A single institution experience [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-17-04.

Abstract PO2-04-01: Predictors of exceptional response to first line HER2-targeted therapy for metastatic breast cancer

Abstract Background HER2-targeted therapies have transformed the trajectory of HER2-positive (HER2+) metastatic breast cancer (MBC), with a subgroup of responders remaining on first line (1L) therapy for many years (yrs). Despite these promising outcomes, the paradigm remains palliative, with some patients (pts) receiving therapy indefinitely. Opportunities to interrupt therapy are controversial and anecdotal in the setting of a limited understanding of long-term responders and lack of predictive biomarkers. Methods We identified prevalent pts with HER2+ MBC seen and consented at Dana-Farber Cancer Institute between 2010 and 2023, regardless of the original date of MBC diagnosis. Exceptional responders (ExRes) were pts without evidence of progressive disease (PD) 3 yrs from initiation of 1L therapy for MBC. Conventional responders (ConRes) were pts who experienced PD within 3 yrs of 1L treatment initiation. We compared clinicopathological characteristics and treatment patterns between ExRes and ConRes using Chi-square or Wilcoxon test. We analyzed median time to treatment switch due to PD (TTS-PD) – i.e., time from metastatic diagnosis to 1L treatment end due to PD - and overall survival, via the Kaplan-Meier method and with a landmark analysis at year 3 (Y3). Our primary aim was to identify predictors of exceptional response to 1L anti-HER2 therapy. Results Of 635 pts with HER2+ MBC, we identified 147 ExRes and 370 ConRes and excluded 118 pts due to follow up ≤ 3 yrs and no PD events. Median follow up was 7.1 yrs (IQR 5.5-11.0) for ExRes and 7.1 yrs (IQR 4.0-11.4) for ConRes. Median age at MBC diagnosis was 50.7 yrs (range 21.9-91.9) for ExRes and 49.8 yrs (26.9-82.3) for ConRes. ExRes presented more often with de novo MBC than ConRes (52.1 vs 30.6%, p< 0.0001). On metastatic samples, more ExRes than ConRes had HER2 3+ tumors by immunohistochemistry (IHC) (93.7 vs 81.0%, p=0.002), whereas the proportion of ER-positive disease was similar between the two groups (45.6 vs 53.4%, p=0.1). Most pts received (neo)adjuvant anti-HER2 agents in both groups (62.5 vs 72.7%, p=0.1). More ExRes than ConRes (55.8 vs 42.7% p=0.007) received 1L chemotherapy (CT) plus trastuzumab (H)/pertuzumab (P). Alternative 1L treatments were CT plus H (26.5 vs 25.7%), H +/- P +/- endocrine therapy (8.2 vs 10.5%), T-DM1 (2 vs 9.2%), tyrosine kinase inhibitors-based regimens (7.5 vs 10.8%). For pts with recurrent MBC, disease-free interval was longer for ExRes than ConRes (median 4.7 vs 3.4 yrs, p=0.01). Visceral involvement at MBC relapse was similar for ExRes and ConRes (78.2 vs 77.8%, p=0.9). Brain metastases at any timepoint were less frequent among ExRes than ConRes (42.9 vs 55.1%, p=0.01). Among ExRes, 70 (47.6%) pts experienced PD after Y3, with a median TTS-PD of 4.6 (4.1-5.1) yrs. In a landmark analysis at Y3, the 2-year TTS-PD was 68.5% (95% CI: 59.8%-75.7%) (5 yrs from treatment start), and 4-year overall survival was 86.5% (95% CI: 78.1%-91.9%) (7 yrs from treatment start). ConRes received a median of 5 (1-19) treatment regimens for MBC, with a median 1L TTS-PD of 12 (10.8-13) mo. A total of 89 (60.5%) ExRes and 214 (57.8%) ConRes underwent tumor sequencing. Data comparing genomic features between ExRes and ConRes will be presented. Conclusions In this prospective cohort, 28% of pts with HER2+ MBC had exceptional response to 1L anti-HER2 therapy. Consistent with prior data, ExRes present more frequently with de novo disease and HER2 IHC 3+ tumors. In our cohort, ExRes had a median follow-up of 7.1 years and 52.4% never experienced PD. Although a significant proportion of pts with HER2+ MBC derive long-term benefit from anti-HER2 therapy, the treatment paradigm remains palliative, and it is unknown whether biomarkers may reliably predict exceptional response and guide future treatment. Ongoing work will explore whether genomic features vary between ExRes and ConRes. Citation Format: Stefania Morganti, Tianyu Li, Katheryn Santos, Melissa Hughes, Nolan Priedigkeit, Yvonne Li, Marla Lipsyc-Sharf, Gregory Kirkner, Janet Files, Julie Kasparian, Elizabeth Grant, Gunjan Gupta, Giuseppe Curigliano, Sara Tolaney, Andrew Cherniack, Nabihah Tayob, Nancy Lin, Heather Parsons. Predictors of exceptional response to first line HER2-targeted therapy for metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-04-01.

Abstract LB009: Unveiling the significance of DARPP-32 and its partners, including GRB7 and DKK1, in breast cancer: Integrative insights from patient data and cell line transcriptomics

Abstract DARPP-32 plays a crucial role in regulating both protein-phosphatase-1 (PP-1) and protein kinase A (PKA), its function being reliant on its phosphorylation status. We have previously demonstrated that low DARPP-32 expression is associated with adverse survival of breast cancer patients, particularly those with oestrogen receptor (ER) positive disease; however, there is limited information on how DARPP-32 may alter breast cancer cell behaviour. We have recently published an integrative approach using patient data and cell line transcriptomics to understand the role of DARPP-32 in breast cancer. We analysed the transcriptome of T47D ER positive breast cancer cells following DARPP-32 knockdown, including treatments in combination with 17β-estradiol or PKA inhibitor fragment (6-22) amide. 202 differentially expressed transcripts were identified in DARPP-32 knock down cells and treatment of these cells with 17β-estradiol or PKA inhibitor fragment (6-22) amide led to the differential expression of 193 and 181 transcripts respectively. Differentially expressed transcripts were compared with genes identified as associated with DARPP-32 expression in 1980 breast cancer patients within the METABRIC cohort using an Artificial Neural Network approach (ANN). Several genes overlapped with those identified from cell line transcriptomics, including PTK7, TRAF5, and KLK6. Both DKK1 and GRB7 were identified as genes associated with DARPP-32 expression in patients using ANN, therefore protein expression was determined in a large cohort of early-stage breast cancer patients (n>1000). We demonstrated that DKK1 and GRB7 protein expression was significantly correlated with DARPP-32 Threonine-34 phosphorylation levels within the same samples (all P<0.05). We have now applied an ANN-based integrative data mining approach to identify genes with the largest effect on other genes resulting in an interactome map, which was based on genes identified within the cell line transcriptomics and original ANN. 1878 genes were identified for inclusion within an interactome map in the total patient cohort, whereas 1003 were identified in ER negative disease alone and 2144 in ER positive disease alone. Pathway enrichment analysis identified the ubiquitin proteosome pathway, the insulin pathway-protein kinase B signalling cascade and the RAS pathway. This study underscores the significance of DARPP-32, a central molecular switch, in breast cancer, elucidating its impact on patient prognosis and highlighting potential molecular targets for therapeutic intervention. The integrative approach combining patient data with cell line transcriptomics provides insights into the complex mechanisms underlying breast cancer progression and opens avenues for further research and targeted interventions. Citation Format: Behnaz Saidy, Richa Vasan, Megan-Rose Greener, Rosie Durrant, Adelynn Immanuel, Andrew Green, Emad Rakha, Ian Ellis, Graham Ball, Stewart Martin, Sarah J. Storr. Unveiling the significance of DARPP-32 and its partners, including GRB7 and DKK1, in breast cancer: Integrative insights from patient data and cell line transcriptomics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB009.

Effect of capecitabine as monotherapy for HER2 normal metastatic breast cancer

This study aimed to evaluate the efficacy of capecitabine monotherapy for patients with human epidermal growth factor receptor-2 (HER2) normal metastatic breast cancer (MBC). The primary endpoint was progression-free survival (PFS), and secondary endpoints included overall survival (OS) and PFS according to treatment line and estrogen receptor (ER) status. Patients who received capecitabine as monotherapy for HER2 normal MBC from 2010 to 2020 were included in this retrospective study. ER status, treatment line, number of treatments, and dates of progression and death were registered. PFS was defined from capecitabine initiation to progression or any cause of death, and OS until any cause of death. Among 162 patients receiving capecitabine, approx. 70% had ER-positive disease. They received a median of six cycles of capecitabine (range 2–45). The median PFS was 4.3 months, with no significant difference between treatment lines. When analyzing PFS according to ER status, a statistically significant difference was observed between those with ER-positive and ER-negative disease, with a median PFS of 5,3 months versus 2,5 months, respectively (p = 0.006). A similar trend was seen for overall survival, with a median OS of 14 months for all patients and 17.8 months versus 7.6 months for patients with ER-positive and ER-negative disease, respectively (p ≤ 0.0001). Patients with HER2 normal MBC receiving monotherapy capecitabine had a median PFS of 4.3 months, and a median OS of 14 months. PFS was consistent regardless of treatment line but differed significantly according to ER status.

Abstract IA18: Genetic susceptibility to breast cancer: Recent advances and application to personalised prevention

Abstract The past two decades have seen dramatic progress in our understanding of the inherited basis of breast cancer, driven by large international collaborative epidemiological studies. Genetic factors identified include rare coding variants in susceptibility genes, and more than 200 common polymorphisms, identified through genome-wide association studies (GWAS) and largely in non-coding regions, that confer more moderate risks. The majority of the common variants are more strongly associated with ER-positive disease, but a subset is specifically associated with ER-negative disease. Variants are strongly enriched for regulatory regions and transcription factor binding sites, and the putative target genes are strongly enriched for known breast cancer drivers: however, the underlying target genes and mechanisms remain largely obscure. The associations for common variants appear to be largely independent of each other and can be summarised by a polygenic risk score (PRS) that is strongly predictive of risk. The most extensively validated PRS, comprising 313 SNPs, is associated with a relative risk of approximately 1.6 per standard deviation; women in the top 1% of the risk distribution have an approximately 4-fold risk of ER-positive disease and 3-fold risk of ER-negative disease. The PRS was developed in women of European ancestry but is also predictive of risk in Asian ancestry women, though less so in African ancestry women. In contrast, despite their widespread use, the evidence for association with cancer for coding variants in genes on genetic testing panels is often weak. Recent very large-scale targeted sequencing studies, however, have clarified the position, providing strong evidence for an association between protein truncating or missense variants and breast cancer risk for nine genes: BRCA1, BRCA2, ATM, CHEK2, PALB2, BARD1, RAD51C, RAD51D and TP53. Recent large-scale exome-wide sequencing analysis has shown that rare variants in several additional genes are also risk associated, with the majority being tumour suppressor genes: these include MAP3K1, ATRIP and SAMHD1. These analyses also demonstrate, however, that the contribution of coding variation, beyond the known genes, is likely to be small. The currently identified variants explain about half of the familial risk of breast cancer. Part of the “missing” heritability is due to weaker common variants, many of which should be identified in ongoing larger GWAS. The causes of the remainder are obscure and may include rare non-coding variants, repeat polymorphisms, and epistatic interactions. Risk discrimination is most powerful when all risk factors are considered. The BOADICEA model, implemented in the CanRisk tool, provides a well validated model that incorporates the effects of gene variants, polygenic risk scores, lifestyle factors and breast density to predict breast and ovarian cancer risk. Multiple translational studies are ongoing to evaluate the feasibility and utility of such personalised risk prediction for stratifying screening and prevention. Citation Format: Douglas F Easton. Genetic susceptibility to breast cancer: Recent advances and application to personalised prevention [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr IA18.

Abstract A017: Perturbation and stability of PAM50 subtyping in population-based primary invasive breast cancer

Abstract PAM50 gene expression subtypes represent a cornerstone in molecular classification of breast cancer and are included in risk prediction models to guide therapy. We aimed to illustrate the impact of included genes and biological processes on subtyping while considering a tumor’s underlying clinical subgroup defined by ER, PR and HER2 status. To do this we used a population-representative and clinically annotated primary breast tumor cohort of 6233 samples profiled by RNA sequencing and applied a perturbation strategy of excluding co-expressed genes (gene sets). We demonstrate how PAM50 nearest centroid classification depends on biological processes present across, but also within, ER/PR/HER2 subgroups and PAM50 subtypes themselves. Our analysis highlights several key aspects of PAM50 classification. Firstly, we observed a tight connection between a tumor’s nearest and second nearest PAM50 centroid. Additionally, we show that second-best subtype is associated with overall survival in ER-positive, HER2-negative, and node negative disease. We also note that ERBB2 has little impact on PAM50 classification in HER2-positive disease regardless of ER-status, and that the Basal subtype is highly stable in contrast to the Normal subtype. Improved consciousness of the commonly used PAM50 subtyping scheme will aid in our understanding and interpretation of breast tumors that have seemingly conflicting PAM50 classification when compared to clinical biomarkers. Finally, our study adds further support in challenging the common misconception that PAM50 subtypes are distinct classes by illustrating that PAM50 subtypes in tumors represent a continuum that may have clinical implications. Citation Format: Srinivas Veerla, Lennart Hohmann, Deborah F. Nacer, Johan Vallon-Christersson, Johan Staaf. Perturbation and stability of PAM50 subtyping in population-based primary invasive breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A017.

Abstract IA26: Exploring breast cancer vulnerabilities through apoptotic pathways

Abstract Combined CDK4/6 inhibitor and endocrine therapy has rapidly become standard therapy for patients with early line relapsed estrogen receptor (ER)-positive, HER2-negative breast cancer. Although this combination has been shown to significantly improve progression free and overall survival, relapse is virtually inevitable. This may in part be due to the profound cytostatic effect of CDK4/6 inhibitors on tumors, which is associated with reduced apoptotic cell death. It seems likely that growth arrested and/or senescent tumor cells acquire resistance to therapy, leading to relapse. BH3 mimetics are an emerging class of drug that target pro-survival proteins such as BCL2, BCL-xL and MCL1. Venetoclax, a BH3 mimetic that has potent and specific activity against BCL2, has shown considerable promise in hematopoietic tumors such as CLL, but has yet to be fully explored in solid tumors. We have previously demonstrated safety and efficacy of combining tamoxifen with venetoclax for patients with metastatic ER-positive BCL2-positive disease using pre-clinical PDX models and a dose-finding phase 1 study [mBEP study, ISRCTN98335443], where most patients were CDK4/6 inhibitor therapy-naïve. In the post-CDK4/6 inhibitor setting, however, venetoclax did not improve clinical benefit rate or progression free survival when added to fulvestrant in the phase 2 study VERONICA [NCT03584009]. In that study a minority of tumours exhibited strong BCL2 expression and exploratory biomarker analysis revealed a trend towards improved progression free survival for patients with tumors exhibiting high BCL2 expression (IHC 3+), a BCL2:BCL-xL Histoscore ratio ≥1, or with PIK3CA wild-type status. Using pre-clinical models including patient derived xenografts of ER-positive breast cancer, we have shown that the addition of venetoclax to dual therapy comprising fulvestrant and the CDK4/6 inhibitor palbociclib elicits a superior and more durable tumor response, accompanied by increased apoptosis. These findings have formed the basis of a phase 1 clinical trial of palbociclib, letrozole and venetoclax [PALVEN, NCT03900884] in patients with early line relapsed ER and BCL2-positive metastatic breast cancer. In parallel, pre-clinical studies are underway to determine the effect of dual targeting BCL-xL and MCL1, as well as dual targeting of AKT and with a BH3 mimetic in CDK4/6 inhibitor refractory breast cancer cells. Citation Format: James R Whittle, François Vaillant, Elliot Surgenor, Luuk Heitink, Christine Muttiah, Jane E Visvader, Geoffrey J Lindeman. Exploring breast cancer vulnerabilities through apoptotic pathways [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr IA26.

Abstract A062: Somatic engineering of rat models to recapitulate human breast cancer evolution and heterogeneity

Abstract Estrogen receptor (ER) positive breast cancer accounts for over 75% of all presenting clinical cases. In addition, almost all Ductal Carcinoma in situ (DCIS) lesions, now accounting for about 25% of all newly diagnosed ‘breast cancers’, are ER-dependent. Despite the high occurrence, the molecular underpinnings regulating DCIS initiation and progression to invasive disease remain elusive. This gap in knowledge is primarily due to the dearth of suitable preclinical models that accurately emulate breast cancer heterogeneity. To overcome this impediment, we developed a platform of somatic models by engineering the rat mammary gland and manipulating the genes most frequently mutated in hormone-dependent (pre-)breast cancer. This has successfully led to the generation of ER-positive disease models that provide a nuanced understanding of ER functionality and the complex mechanisms of ER signaling, which we show to be dependent on the cancer genotype. This has potential implications for the formulation of innovative endocrine therapy treatment regimens. Our models have generated an array of tumor types, including ductal and lobular carcinomas, manifesting both in situ and invasive phenotypes, faithfully recapitulating human breast disease and the evolution of tumorigenesis. Intriguingly, our results indicate how different oncogenic mutations modulate not only the architectural and histopathological characteristics of cancer but also the immune microenvironment, thereby generating possibilities for future therapeutic testing. Our research augments the range of available ER-positive in situ and invasive breast cancer models, benefitting the stratification of indolent from aggressive disease and facilitating the exploration of novel treatment strategies for this pervasive breast cancer subtype. Citation Format: Catrin Lutz, Ji-Ying Song, Hendrik A Messal, Madelon Badoux, Timo Eijkman, Bim de Klein, Jelle Wesseling, Jos Jonkers. Somatic engineering of rat models to recapitulate human breast cancer evolution and heterogeneity [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr A062.

An updated PREDICT breast cancer prognostic model including the benefits and harms of radiotherapy

PREDICT Breast (www.breast .predict.nhs.uk) is a prognostication tool for early invasive breast cancer. The current version was based on cases diagnosed in 1999–2003 and did not incorporate the benefits of radiotherapy or the harms associated with therapy. Since then, there has been a substantial improvement in the outcomes for breast cancer cases. The aim of this study was to update PREDICT Breast to ensure that the underlying model is appropriate for contemporary patients. Data from the England National Cancer Registration and Advisory Service for invasive breast cancer cases diagnosed 2000–17 were used for model development and validation. Model development was based on 35,474 cases diagnosed and registered by the Eastern Cancer Registry. A Cox model was used to estimate the prognostic effects of the year of diagnosis, age at diagnosis, tumour size, tumour grade and number of positive nodes. Separate models were developed for ER-positive and ER-negative disease. Data on 32,408 cases from the West Midlands Cancer Registry and 100,551 cases from other cancer registries were used for validation. The new model was well-calibrated; predicted breast cancer deaths at 5-, 10- and 15-year were within 10 per cent of the observed validation data. Discrimination was also good: The AUC for 15-year breast cancer survival was 0.809 in the West Midlands data set and 0.846 in the data set for the other registries. The new PREDICT Breast model outperformed the current model and will be implemented in the online tool which should lead to more accurate absolute treatment benefit predictions for individual patients.

Clinical and economic outcomes of adding [18F]FES PET/CT in estrogen receptor status identification in metastatic and recurrent breast cancer in the US.

Correct identification of estrogen receptor (ER) status in breast cancer (BC) is crucial to optimize treatment; however, standard of care, involving biopsy and immunohistochemistry (IHC), and other diagnostic tools such as 2-deoxy-2-[18F]fluoro-D-glucose or 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG), can yield inconclusive results. 16α-[18F]fluoro-17β-fluoroestradiol ([18F]FES) can be a powerful tool, providing high diagnostic accuracy of ER-positive disease. The aim of this study was to estimate the budget impact and cost-effectiveness of adding [18F]FES PET/CT to biopsy/IHC in the determination of ER-positive status in metastatic (mBC) and recurrent breast cancer (rBC) in the United States (US). An Excel-based decision tree, combined with a Markov model, was developed to estimate the economic consequences of adding [18F]FES PET/CT to biopsy/IHC for determining ER-positive status in mBC and rBC over 5 years. Scenario A, where the determination of ER-positive status is carried out solely through biopsy/IHC, was compared to scenario B, where [18F]FES PET/CT is used in addition to biopsy/IHC. The proportion of true positive and true negative test results increased by 0.2 to 8.0 percent points in scenario B compared to scenario A, while re-biopsies were reduced by 94% to 100%. Scenario B resulted in cost savings up to 142 million dollars. Adding [18F]FES PET/CT to biopsy/IHC may increase the diagnostic accuracy of the ER status, especially when a tumor sample cannot be obtained, or the risk of a biopsy-related complication is high. Therefore, adding [18F]FES PET/CT to biopsy/IHC would have a positive impact on US clinical and economic outcomes.

Perturbation and stability of PAM50 subtyping in population-based primary invasive breast cancer

PAM50 gene expression subtypes represent a cornerstone in the molecular classification of breast cancer and are included in risk prediction models to guide therapy. We aimed to illustrate the impact of included genes and biological processes on subtyping while considering a tumor’s underlying clinical subgroup defined by ER, PR, and HER2 status. To do this we used a population-representative and clinically annotated early-stage breast tumor cohort of 6233 samples profiled by RNA sequencing and applied a perturbation strategy of excluding co-expressed genes (gene sets). We demonstrate how PAM50 nearest-centroid classification depends on biological processes present across, but also within, ER/PR/HER2 subgroups and PAM50 subtypes themselves. Our analysis highlights several key aspects of PAM50 classification. Firstly, we demonstrate the tight connection between a tumor’s nearest and second-nearest PAM50 centroid. Additionally, we show that the second-best subtype is associated with overall survival in ER-positive, HER2-negative, and node-negative disease. We also note that ERBB2 expression has little impact on PAM50 classification in HER2-positive disease regardless of ER status and that the Basal subtype is highly stable in contrast to the Normal subtype. Improved consciousness of the commonly used PAM50 subtyping scheme will aid in our understanding and interpretation of breast tumors that have seemingly conflicting PAM50 classification when compared to clinical biomarkers. Finally, our study adds further support in challenging the common misconception that PAM50 subtypes are distinct classes by illustrating that PAM50 subtypes in tumors represent a continuum with prognostic implications.

No evidence for a genetic causal effect of breast cancer on venous thromboembolism: a mendelian randomization study.

Active cancer is known to contribute to venous thromboembolism (VTE), but the cause-and-effect association of breast cancer on VTE is not yet clear. In order to investigate the possible causal relationships, we used a Mendelian randomization analysis. Data for generically predicted breast cancer were identified based on the BCAC consortium. A meta-analysis of genome-wide association study (GWAS) comprising 1,500,861 participants for VTE as well as data from the FinnGen study for VTE, DVT and PE was used for the causal-effect estimation. Our primary method was inverse-variance weighted (IVW), and our supplementary methods included weighted median and MR-Egger. We also carried out sensitivity analysis for the study. No evidence of causal-effect was detected of overall breast cancer on VTE in both the GWAS meta-analysis (OR=1.01, 95%CI:0.98-1.04, p = 0.495) and the FinnGen consortium (OR=1.00,95%CI:0.96-1.04, p = 0.945). In addition, the presence of ER-positive or ER-negative disease did not significantly influence the incidence of VTE and its subtypes. In conclusion, no genetic cause-and-effect of breast cancer on VTE risk was detected in the large MR analysis.

Hounsfield Units Predict Survival of Patients With Estrogen Receptor-Positive and Human Epithelial Growth Factor Receptor 2-Negative Breast Cancer

BackgroundsTumor vascularity plays a fundamental role in cancer progression, including breast cancer. This study aimed to elucidate tumor vascularity and its impact on patient survival in the context of breast cancer subtypes using Hounsfield units (HU) on contrast-enhanced computed tomography (CT). Materials and methodsPatients with early-stage breast cancer who completed planned treatment between 2003 and 2013 were retrospectively assessed. ResultsThe final cohort comprised 440 patients. Of the 440 patients, 262 had estrogen receptor (ER)-positive disease and 119 had human epidermal growth factor receptor 2 (HER2)-overexpressing disease. The tumor-to-aorta ratio of Hounsfield units (TAR) was related to significantly worse recurrence-free interval (RFI) (P < .001) and overall survival (OS) (P < .001) in patients with TAR > 0.33 for RFI and > 0.35 for OS than their counterparts. In the subgroup analysis, the survival disadvantage was limited only to patients with ER-positive and HER2-negative disease (P < .001 for both RFI and OS). ConclusionThis study showed that TAR, which reflects tumor vascularity, was significantly related to patients’ RFI and OS, suggesting its capacity as a feasible biomarker. This study also showed that TAR was associated with the survival in patients with ER-positive and HER2-negative disease.