Negative Hormone Receptor Status Research Articles

Excluding Upper Axillary Level 1 in Regional Nodal Irradiation Does Not Increase Axillary Recurrence Risk in Patients With Breast Cancer

PurposeThe optimal extent of regional nodal irradiation (RNI) in postoperative radiotherapy for breast cancer, particularly regarding axillary level 1 (AXL1), remains uncertain. This study aims to compare clinical outcomes between extensive RNI including the entire axilla and limited RNI excluding the upper AXL1 in patients with breast cancer. MethodsA retrospective analysis included 1,780 women with non-metastatic unilateral breast cancer who underwent RNI during postoperative radiotherapy between 2007 and 2018. Patients were classified into extensive and limited RNI groups based on the upper AXL1 inclusion in the radiation field. Propensity score matching yielded a cohort of 1,020 patients. Non-inferiority of limited RNI compared to extensive RNI was assessed with a defined margin of ≤2% in the 5-year axillary recurrence rate. ResultsAfter a median follow-up of 67.9 months, the 5-year axillary recurrence rates were similar between extensive and limited RNI groups (1.2% vs. 1.6%; Plog-rank=0.790). Limited RNI demonstrated non-inferiority with a 0.4% difference (95% confidence interval, -1.1%–1.9%; Pnon-inferiority=0.019). Disease-free survival (87.9% vs. 91.5%; Plog-rank=0.122) and overall survival (94.1% vs. 96.9%; Plog-rank=0.260) at 5 years were not significantly different between extensive and limited RNI groups. Multivariable analysis revealed that lymphovascular invasion (hazard ratio [HR], 5.17; P=0.02) and negative hormone receptor status (HR, 11.73; P=0.002) were associated with a higher risk of axillary recurrence, while limited RNI showed no significant association (HR, 1.35; P=0.652). Subgroup analysis demonstrated that extensive RNI did not improve axillary control in patients with lymphovascular invasion, hormone receptor negativity, positive lymph node metastasis, or a small number of nodes removed. ConclusionLimited RNI, excluding the upper AXL1 from the radiation field, demonstrated axillary recurrence rates comparable to those of extensive RNI in patients with breast cancer. The study suggests that extensive RNI may not provide additional therapeutic benefits, while limited RNI appears to be a valid option for regional control.

Survival outcomes of neoadjuvant versus adjuvant therapy in patients with T1c, node‐negative, human epidermal growth factor receptor 2–positive breast cancer: A Surveillance, Epidemiology, and End Results population‐based study

AbstractBackgroundPersistent debates exist regarding the superiority of neoadjuvant therapy (NAT) over adjuvant therapy (AT) for patients with T1c, node‐negative, human epidermal growth factor receptor 2–positive (HER2+) breast cancer, and relevant guidelines for these patients are lacking.MethodsData on patients with T1cN0M0‐stage HER2+ breast cancer who received chemotherapy and surgery were extracted from 2010 to 2020 from the Surveillance, Epidemiology, and End Results database. Propensity score matching (PSM) was used to create well‐balanced cohorts for the NAT and AT groups. Kaplan–Meier (KM) analysis and Cox proportional hazards models were used to assess the differences between NAT and AT in terms of overall survival (OS) and breast cancer–specific survival (BCSS). Additionally, logistic regression models were used to explore factors associated with response to NAT.ResultsAfter PSM, 2140 patient pairs were successfully matched, which achieved a balanced distribution between the NAT and AT groups. KM curves revealed similar OS and BCSS between patients receiving NAT and those undergoing AT. A multivariate Cox model identified achieving pathological complete response (pCR) after NAT, compared with AT, as a protective prognostic factor for OS (hazard ratio, 0.52; 95% CI, 0.35–0.77; p < .001) and BCSS (hazard ratio, 0.60; 95% CI, 0.37–0.98; p = .041). A logistic regression model revealed that White race and hormone receptor–negative status independently predicted pCR.ConclusionsFor patients with T1cN0M0‐stage HER2+ breast cancer, NAT demonstrated comparable OS and BCSS to AT. Patients who achieved pCR after NAT exhibited significantly better survival outcomes compared with those who received AT.

Prognostic and predictive impact of NOTCH1 in early breast cancer.

Systemic therapy plays a major part in the cure of patients with early breast cancer (eBC). However, personalized treatment concepts are required to avoid potentially harmful overtreatment. Biomarkers are pivotal for individualized therapy. The Notch signalling pathway is widely considered as a suitable prognostic or predictive marker in eBC. This study aimed primarily at assessing the relationship between NOTCH1 mRNA expression levels and histopathological features of breast cancer tumors, as well as clinical characteristics of the correspondent eBC patients. As a secondary aim, we investigated the prognostic and predictive value of NOTCH1 by assessing possible associations between NOTCH1 mRNA expression and recurrence-free interval (RFI) and overall survival after five years of observation. The relative NOTCH1 mRNA expression was determined in 414 tumour samples, using quantitative PCR in a prospective, multicenter cohort (Prognostic Assessment in Routine Application (PiA), 2009-2011, NCT01592825) of 1,270 female eBC patients. High NOTCH1 mRNA expression was detected in one-third of the tumours and was associated with negative hormone receptor status and high uPA/PAI-1 status. In addition, high NOTCH1 mRNA expression was found to be associated with more RFI related events (adjusted hazard ratio 2.1, 95% CI 1.077-4.118). Patients who received adjuvant chemotherapy and had high NOTCH1 mRNA expression in the tumour (n = 86) were three times more likely to have an RFI event (adjusted hazard ratio 3.1,95% CI 1.321-7.245, p = 0.009). In this cohort, NOTCH1 mRNA expression had a prognostic and predictive impact. Tumours with high NOTCH1 mRNA expression may be less sensitive to cytotoxic treatment and downregulation of the Notch signalling pathway (e.g. by γ-secretase inhibitors) may be valuable for eBC therapy as an individualised treatment option.

Racial disparities in presentation and survival for lobular breast cancer.

1596 Background: We characterized differences in presentation and survival, and identified predictors of survival, among women of varying race with lobular breast cancer. We also assessed if these trends were unique to ILC by comparing with invasive ductal carcinoma (IDC) and mixed invasive ductal-lobular carcinoma (IDLC). Methods: Using the SEER database, we performed a population-based retrospective cohort study of women diagnosed with ILC, IDC, and IDLC between 1998 and 2019. We collected race, age, marital status, and income. Clinical data included grade, size, laterality, clinical stage, receptor status, surgery type, chemotherapy, radiation, and breast-cancer-specific survival (BCSS). Differences between racial groups were assessed using Chi-square tests or one-way ANOVA. To identify predictors of survival, Cox-proportional hazard models were constructed. Statistical analyses were performed using SAS and P values < 0.05 were considered significant. Results: 38,769 women with ILC were identified, including 32,857 White, 2398 Black, 2352 Asian, and 1162 women of other race. Black women presented with higher-grade, advanced clinical stage, ER+ disease, N2-3 stage, and lower rates of unilateral/bilateral mastectomy than White women. Black women were more likely to not undergo surgery (7.13%), compared with White (4.25%) and Asian (4.04%) women ( P = .0001). Asian women were younger, had more ER-/PR- ILC, and received more chemotherapy. The five-year BCSS rates in Black, White, Asian, and women of other race were 91.5%, 94.2%, 93.7%, and 95.7%, respectively ( P< .0001). Predictors of worse survival include Black race (HR 1.32, P < .0001), ER-/PR- (HR 2.18, P< .0001), ER+/PR- (HR 1.52, P< .0001), and no surgery (HR 4.19, P < .0001). Radiotherapy was associated with improved survival (HR 0.82, P < .0001), while chemotherapy did not affect survival (HR 1.1, P= 0.0504). In comparing across breast cancer subtypes, Black women similarly present with higher grade tumors, advanced clinical stage, ER+ disease, and had higher rates of surgery omission in IDC and IDLC. However, ER-/PR- subtype was notably higher in ILC among Asian women compared with IDC, whereas Black women have higher rates of ER+/PR+ and ER-/PR- ILC. Black women had the lowest five-year BCSS rates across all breast cancer subtypes. Predictors of worse survival in IDC and IDLC include Black race and negative hormone receptor status, while radiation therapy was associated with improved survival. Conclusions: There are differences in clinical presentation of invasive lobular breast cancer according to race.Black women had more advanced disease, while Asian women were younger. Across all subtypes, overall survival for Black women at 5 years was worse compared to other racial groups. Our data provides insight into the complex interactions of race, clinical characteristics, and survival outcomes in lobular breast cancer, with implications for screening considerations.

Abstract PO5-23-04: Clinical utility of sentinel lymph node biopsy in women ≥ 70 years with early breast cancer – an international, retrospective multi-center cohort study

Abstract Introduction Traditionally, sentinel lymph node biopsy (SLNB) has been used to stage the axilla in early breast cancer (EBC) to guide adjuvant treatment recommendations. Following advances in tumor biology understanding, targeted systemic therapies and genomic testing, with increasing de-escalation of axillary surgery, its role may be less critical especially in selected groups of women. Aims Evaluate clinical utility of SLNB in adjuvant treatment recommendations for women ≥ 70 years with EBC. Methods Retrospective cohort study of women ≥ 70 years with cT1-2N0 EBC undergoing primary surgery and SLNB between 01/2017-12/2022 at The Royal Marsden Hospital (RMH), University Hospital Zurich (USZ) and Seoul National University Hospital (SNUH) in the United Kingdom, Switzerland and South Korea respectively. Simple descriptive statistics and non-parametric tests were performed as appropriate. Results A total of 884 patients were included in the analysis, with 584 patients from RMH, 148 from USZ and 152 from SNUH. The median age was 75 (IQR 72-79) years. Most cancers were invasive ductal (82.9%), grade 2 (61.4%), hormone receptor (HR) positive/HER2 negative (82.9%) with a median tumor size of 17 (IQR 4-50) mm. SLNB was positive in 116 (13.1%) patients. Of these 116 patients, 20 (17.2%) had completion ALND; 7/20 had further RT up to levels 3&4 of the axilla. Of these 116 patients, 96 patients (82.8%) avoided ALND; 25/96 had no further treatment, and 71/96 patients had loco-regional axillary RT (8/71 had RT to levels 1&2 and 63/71 had RT up to levels 3&4). As per international guidelines for patients with EBC with 1-2 positive macrometastases on SLNB treated with breast conserving surgery and breast RT, 5/20 could have been spared ALND, and 50/71 axillary RT. Completion ALND was more likely to be performed at SNUH compared to the other 2 units (p< 0.0001). Axillary RT was more likely to be administered at SNUH and less likely at RMH (p< 0.0001). The multidisciplinary team (MDT) recommended adjuvant chemotherapy (AC) in 146 (16.5%) patients and 100 received it. Of those with a positive SLNB (n=116), AC was recommended in 35, and received by 29. Recommendation for AC was significantly associated with younger age (p=0.021), fewer comorbidities (p=0.003), higher tumor grade (p< 0.0001), increased tumor size (p< 0.0001), HR negative status (p< 0.0001), high genomic risk profile (p< 0.0001) and positive SLNB status (p< 0.0001), but not center (p=0.497). A subgroup analysis of 505 patients with cT1N0, HR+/HER2- EBC, representing a more favorable prognosis group, was performed. Here, 52/505 (10.3%) patients had positive SLNB, of whom 11 had no further axillary treatment, 9 underwent ALND and 32 axillary RT, where 4/9 could have been spared ALND and 28/32 axillary RT as per international guidelines mentioned above. AC was recommended in 26/505 (5.15%) women and 23 received it. AC was not recommended in 39/52 (75%) cases, despite a positive SLNB. MDT recommendation for AC was associated with grade 3 (p< 0.0001), multifocal disease (p=0.021), positive SLNB status (p< 0.0001), high genomic risk profile (p< 0.0001), lower age (p=0.044), fewer co-morbidities (p=0.001) and center (p=0.007) with SNUH being more likely than the other 2, but not ethnicity (p=0.130); AC receipt was associated with the same factors except age (p=0.347). Conclusions Real-world data demonstrates axillary overtreatment despite evidence of the safety of de-escalation of axillary management in EBC. Only a small proportion of women ≥ 70 years with EBC had positive SLNB that may influence adjuvant treatment recommendations, especially with favorable prognosis tumors. In such cases, where clinical morbidity and financial burden of SLNB may outweigh the benefits, a nuanced discussion for opting in SLNB rather than routine performance should be considered. Citation Format: Radhika Merh, Denise Vorburger, Ji-Jung Jung, Han-Byoel Lee, Marios Tasoulis. Clinical utility of sentinel lymph node biopsy in women ≥ 70 years with early breast cancer – an international, retrospective multi-center cohort study [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 PO5-23-04.

Abstract PO5-06-01: Loss of hormone receptor expression in breast cancer is associated with increased brain tropism and accelerated progression of leptomeningeal disease

Abstract The four breast cancer subtypes—luminal A, luminal B, HER2-overexpressing, and triple-negative breast cancer (TNBC) – are classified based on gene expression profiles of hormone receptors (HRs) (estrogen receptor (ER) and progesterone receptor (PR)) and human epidermal growth factor receptor 2 (HER2/ERBB2). Negative hormone receptor status is known to be associated with more aggressive breast cancer. Compared to other breast cancer subtypes, the HR-negative TNBC and HER2-overexpressing subtypes are characterized by high rates of recurrence and a notable increase in brain metastases and in particular, leptomeningeal disease (LMD). LMD – the most aggressive form of central nervous system (CNS) metastasis, in which cancer cells infiltrate leptomeninges of the brain and spine – carries a dismal prognosis due to a rapid progression, poor detection, and no effective treatment. Several studies that investigated the link between HR status and LMD suggest that HR-negative breast cancers have a shorter time to LMD diagnosis. This shortened timeline is consistent with higher migratory capabilities reported for TNBC and HER2 breast cancer cells. However, as it is known that breast cancers exhibit subtype-specific metastatic tropism (i.e., luminal subtypes tend to metastasize to bone and liver, while TNBCs metastasize to the CNS), the longer time between primary breast cancer diagnosis and LMD diagnosis for HR-positive breast cancers may also reflect a longer metastatic route that first includes a non-CNS location. In this study, we performed a retrospective analysis on 141 breast cancer patients with LMD treated at Stanford Hospital between 2008-2020. The Stanford LMD cohort was analyzed using linear regression analysis, Cox regression analysis, and Chi-squared analysis. HR status was recorded (when available) for local recurrences and distant metastases, and was included in our regression models as a time-dependent HR covariate. We tested if: (1) HR-negative breast cancers had shorter time between primary and LMD diagnosis as well as worse survival after LMD diagnosis versus HR-positive breast cancers, and if (2) HR loss (i.e., HR status changing from positive to negative) increased likelihood of the metastasis to CNS. In agreement with published studies, the Stanford LMD cohort showed that HR-negative cancers had shorter time to development of LMD (p = 0.0004 for ER, p = 0.0001 for PR) and increased mortality following LMD (p = 0.010 for ER, p = 0.009 for PR). We found that HR-negative status at primary breast cancer diagnosis increased risk of first metastasis to CNS versus non-CNS locations (p = 0.021 for ER, p = 0.043 for PR). HR status switch (also known as hormone discordance) between primary diagnosis and metastasis occurred in 15% of patients in Stanford cohort, consistent with other studies. Importantly, accounting for HR status switch strengthened the association between HR-negative status and the risk of CNS metastasis [Hazard Ratio = 2.506 (1.395 - 4.500) for “baseline ER status” versus Hazard Ratio = 3.509 (1.890 - 6.515) for “time-dependent ER status”, Hazard Ratio = 2.420 (1.310 - 4.471) for “baseline PR status” versus Hazard Ratio = 3.407 (1.815 - 6.395) for “time-dependent PR status”]. In conclusion, HR-negative status was associated with shorter time to development of LMD, higher CNS tropism, and shorter survival following LMD diagnosis. Taking into consideration hormone discordance between the primary tumor and metastatic sites strengthened this association. Our results suggest a potential value in testing HR status at all recurrences and advanced CNS monitoring following HR loss. Citation Format: Sophia Pribus, Maxine C. Umeh-Garcia, Bo Gu, Bryanna Godfrey, Summer Han, Sophia Chernikova, Melanie Hayden Gephart. Loss of hormone receptor expression in breast cancer is associated with increased brain tropism and accelerated progression of leptomeningeal disease [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 PO5-06-01.

Abstract PO1-25-03: Programmed Death-Ligand 1 and Receptor Tyrosine Kinases in Breast Cancer

Abstract Programmed death-ligand 1 (PD-L1) is an immune checkpoint expressed in a wide range of malignancies leading to immune tolerance and cancer cell immune evasion. Receptor tyrosine kinases (RTKs) are key regulators of cancer cell proliferation, survival, and invasion. The Hepatocyte Growth Factor (HGF) receptor, MET, and the Epidermal Growth Factor Receptor (EGFR) are RTKs known for their tumorigenic potential in a variety of human malignancies. This study aimed to evaluate the effect of the small-molecule tyrosine kinase inhibitors (TKIs) on the expression of PD-L1 in breast cancer cells and the effect of their combination with inflammatory cytokines. The study also assessed the association of the expression of the tumoral PD-L1 mRNA with each of MET and EGFR mRNA expression and the tumor features and treatment outcomes in breast cancer patients using the METABRIC dataset publicly available from cBioPortal for Cancer Genomics. The TKIs crizotinib [a MET inhibitor] and gefitinib [an EGFR inhibitor] were used as a single treatment and in combination with the cytokines; tumor necrosis factor-α (TNF-α) or interferon-γ (INF-γ) in MCF7 and MDA-MB-231 breast cancer cells in vitro. The cells were also treated with the mitogens HGF and EGF. The viability of cells after the different treatments was determined using the MTT viability assay. The effects of the combination treatments were analyzed using combination index (CI) analysis. The expression level of PD-L1 in cancer cells was assessed using Western blotting. The combination treatment of crizotinib with TNF-α and INF-γ produced a synergistic growth inhibition of MCF7 and MDA-MB-231 cells with CI values of 0.31 and 0.55, respectively. Alternatively, combined crizotinib and TNF-α produced an antagonist effect on the viability of MCF7 cells (CI=2.49). The combination of gefitinib with TNF-α produced a synergistic growth inhibition in both MCF7 and MDA-MB-231 cells with CI values of 0.39 and 0.78, respectively. Alternatively, gefitinib resulted in an additive effect when combined with INF-γ (CI=0.99) and an antagonistic effect when combined with TNF-α (CI=2.68) in MCF7 and MDA-MB-231 cells, respectively. Treatment with HGF (50 and 100 ng/ml) increased the protein levels of PD-L1 while EGF (50 and 100 ng/ml) reduced its levels in MDA-MB-231 cells. Treatment with the TKIs crizotinib (0.1-4 µM) and gefitinib (1-40 µM) significantly reduced PD-L1 levels in MDA-MB-231 cells compared to vehicle-treated cells. The analysis of the METABRIC dataset revealed that the mRNA expression of PD-L1 was positively correlated with the mRNA expression of the EGFR gene (r= 0.081, p< 0.001) but not the MET gene. A double-high PD-L1/MET expression was significantly associated with younger age at diagnosis, high-grade carcinoma, greater tumor size, hormone receptor-negative status, HER2-positivity, and non-luminal disease compared to patients with a double-low PD-L1/MET expression. Similar findings were reported for patients with a double-high PD-L1/EGFR expression compared to patients with a double-low PD-L1/EGFR expression. Nevertheless, the mRNA expression of the PD-L1, MET, and EGFR genes as well as the co-expression of PD-L1/MET or PD-L1/EGFR genes did not affect the overall survival of breast cancer patients. Collectively, MET and EGFR TKIs could modulate the effects of inflammatory cytokines differently based on the type of cytokine and the molecular subtype of breast cancer cells. The expression of PD-L1 in breast cancer cells was upregulated by HGF while TKIs reduced its expression. The co-expression of the PD-L1 gene with MET and EGFR genes in breast cancer was associated with advanced disease presentation and worse prognosticators in patients. Together, TKIs that target MET or EGFR could be an appealing therapeutic target in breast cancer, particularly in younger patients with the non-luminal disease. Citation Format: Nehad Ayoub, Muhsen Al-Diabat, Moath Al-Shorman, Laith Al-Eitan. Programmed Death-Ligand 1 and Receptor Tyrosine Kinases in 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 PO1-25-03.

Abstract PO2-01-07: Real-world efficacy of dual HER2-blockade in combination with anthracycline-containing and anthracycline-free neoadjuvant treatment in early breast cancer (BC)

Abstract BACKGROUND: Neoadjuvant therapy with antiHER-2 blockade is the standard of care for HER-2 positive early BC. The objective of this treatment is tumor downstaging to increase resectability and pathological complete response (pCR), a reliable surrogate endpoint for survival. Adding Trastuzumab (T) to chemotherapy resulted in an improvement in pCR, however, resistance to this agent is common and the incorporation of Pertuzumab (P) to the neoadjuvant scene demonstrated an increase in pCR in the Peony (39.3% vs 21.8%) and Neosphere trials (45.8% vs 29%). Across all studies, pCR is even higher in patients (pts) with negative hormonal receptor (HR) status (50%-63%) (3, 4). Tryphaena and Berenice found low rates of cardiotoxicity with T-P combination. Recently, TRAIN-2 data showed that anthracyclines and platinum have a similar pCR (67% vs 68%), but febrile neutropenia and cardiotoxicity is higher in the anthracycline group, concluding that omitting this therapy might be a preferred approach in the presence of dual HER2 blockade. Our study investigated the pCR benefit of dual HER2 blockade with anthracyclines and platinum in HER2 positive early BC. METHODS: We conducted a retrospective, unicenter, observational study of pts, treated with neoadjuvant T-P plus chemotherapy, in HER-2 positive early BC, between April 2015 and December 2022 at University Hospital A Coruña (Spain). The primary endpoint was total pCR in breast and axila (tpCR: ypT0/is ypN0). Secondary endpoints were: association between clinicopatological characteristics and pCR; and between cardiotoxicity and treatment pattern. Statistical analyses were conducted with Statistical Package for the Social Science (SPSS). RESULTS: During the study period, from April 2015 to May 2022, 154 pts were enrrolled. The median age was 51,3 years [range 26 – 799 years], all patients were female. Infiltrating ductal carcinoma was present in 92.2% pts, and 5.8% were inflammatory BC. At diagnosis, 11.7%, 61.7% and 26.6% had stages I, II and III, respectively, and 51.3% revealed axillary node involvement. Among observed cases, 94 (61%) were positive HR; 68 (45%) had histological grade 2 and 83 (53.9%) histological grade 3 tumors; and 151 pts (99.3%) presented a ki-67 level >20%. HER2 by immunohistochemistry (IHC) resulted in 3+ for 133 pts (86.9%) and in 2+ for 20 pts (13.1%), all of them with positive result by in situ hybridation (ISH). P-T were mostly combined with anthracyclines (64.9%). tpCR rate was 50.6%, and it was not significantly different according chemotherapy approach. tpCR was significantly higher among HR negative tumours (73.3%) compared with HR positive (36.2%) (p= 0.001), and in HER2 positive 3+ (55.6%) compared with HER2 positive 2+ (15%) tumours (p= 0.001). Achievement of tpCR was not significantly associated with tumor size, stage, histological grade and ki-67 level. Breast pCR was higher than tpCR (54.2%). 13 pts (8.4%) presented recurrence disease, in 76.9% of cases was a metastatic relapse. Cardiotoxicity was low during all stages of treatment and was not significantly associated with chemotherapy pattern. CONCLUSIONS: Neoadjuvant T-P plus chemotherapy with either anthracyclines or platinum therapy, demonstrated same efficacy and cardiac safety in our real-world study. pCR rates are lower in positive HR and HER2 positive 2+, needing more investigation with combination strategies including hormonotherapy, Our results are similar to data from randomized trials and other real-world efficacy studies, but we need more follow-up to identify late cardiotoxicity by anthracyclines and recurrences in positive HR tumors. Citation Format: Beatriz Alonso de Castro, Cristina Reboredo, Lourdes Calvo, Maria-Eva Perez-Lopez, Martin Igor Gomez Randulfe Rodriguez, Sofia silva diaz, Iria Parajo Vazquez, Silvia Antolin Novoa. Real-world efficacy of dual HER2-blockade in combination with anthracycline-containing and anthracycline-free neoadjuvant treatment in early breast cancer (BC) [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 PO2-01-07.

Clinicopathological and molecular predictors of [18F]FDG-PET disease detection in HER2-positive early breast cancer: RESPONSE, a substudy of the randomized PHERGain trial

BackgroundThe PHERGain study (NCT03161353) is assessing early metabolic responses to neoadjuvant treatment with trastuzumab-pertuzumab and chemotherapy de-escalation using a [18Fluorine]fluorodeoxyglucose-positron emission tomography ([18F]FDG-PET) and a pathological complete response-adapted strategy in HER2-positive (HER2+) early breast cancer (EBC). Herein, we present RESPONSE, a PHERGain substudy, where clinicopathological and molecular predictors of [18F]FDG-PET disease detection were evaluated.MethodsA total of 500 patients with HER2 + EBC screened in the PHERGain trial with a tumor size > 1.5 cm by magnetic resonance imaging (MRI) were included in the RESPONSE substudy. PET[−] criteria entailed the absence of ≥ 1 breast lesion with maximum standardized uptake value (SUVmax) ≥ 1.5 × SUVmean liver + 2 standard deviation. Among 75 PET[−] patients screened, 21 with SUVmax levels < 2.5 were randomly selected and matched with 21 PET[+] patients with SUVmax levels ≥ 2.5 based on patient characteristics associated with [18F]FDG-PET status. The association between baseline SUVmax and [18F]FDG-PET status ([−] or [+]) with clinicopathological characteristics was assessed. In addition, evaluation of stromal tumor-infiltrating lymphocytes (sTILs) and gene expression analysis using PAM50 and Vantage 3D™ Cancer Metabolism Panel were specifically compared in a matched cohort of excluded and enrolled patients based on the [18F]FDG-PET eligibility criteria.ResultsMedian SUVmax at baseline was 7.2 (range, 1–39.3). Among all analyzed patients, a higher SUVmax was associated with a higher tumor stage, larger tumor size, lymph node involvement, hormone receptor-negative status, higher HER2 protein expression, increased Ki67 proliferation index, and higher histological grade (p < 0.05). [18F]FDG-PET [−] criteria patients had smaller tumor size (p = 0.014) along with the absence of lymph node involvement and lower histological grade than [18F]FDG-PET [+] patients (p < 0.01). Although no difference in the levels of sTILs was found among 42 matched [18F]FDG-PET [−]/[+] criteria patients (p = 0.73), [18F]FDG-PET [−] criteria patients showed a decreased risk of recurrence (ROR) and a lower proportion of PAM50 HER2-enriched subtype than [18F]FDG-PET[+] patients (p < 0.05). Differences in the expression of genes involved in cancer metabolism were observed between [18F]FDG-PET [−] and [18F]FDG-PET[+] criteria patients.ConclusionsThese results highlight the clinical, biological, and metabolic heterogeneity of HER2+ breast cancer, which may facilitate the selection of HER2+ EBC patients likely to benefit from [18F]FDG-PET imaging as a tool to guide therapy.Trial registrationClinicaltrials.gov; NCT03161353; registration date: May 15, 2017.

Clinicopathological factors affecting response and survival in stage III breast cancer patients undergoing a dose-dense neoadjuvant regimen.

Identifying predictors of pathological complete response (pCR) and long-term outcomes after neoadjuvant treatment for breast cancer is needed to individualize treatment and patient monitoring. This study aimed to investigate clinicopathological factors affecting pCR and long-term outcomes in stage III breast cancer patients receiving a dose-dense neoadjuvant regimen. This is a retrospective study including patients with stage III breast cancer who received neoadjuvant chemotherapy consisting of doxorubicin 60 mg/m² plus cyclophosphamide 600 mg/m², followed by paclitaxel 175 mg/m² every two weeks at Vietnam National Cancer Hospital and Hanoi Oncology Hospital between January 2015 and December 2022. Logistic and Cox regression were used to investigate the association between clinicopathological factors and pCR and long-term outcomes, respectively. A total of 211 patients were included in the study. Univariate analysis found an association of pCR with clinical tumor (cT) stage, grade, hormone receptor status, HER2, Ki67, and St. Gallen classification. Multivariate analysis identified several predictors of pCR: cT stage (cT3/T4 vs cT1/T2: OR: 0.3; p = 0.01); grade (grade 3 vs grade 1-2: OR: 1.6; p = 0.035); and hormone receptor status (nega-tive vs. positive: OR: 2.9; p = 0.011). Two independent prognostic factors for event-free survival (EFS) were identified: hormone receptor status (negative vs. positive: HR: 2.1; p = 0.044) and pCR (No pCR vs. pCR: HR: 3.0; p = 0.018). Hormone receptor status was also the only independent prognostic factor for overall survival (OS) (negative vs. positive: HR: 2.6; p=0.039). Low cT stage, grade 3, and hormone receptor-negative status were independent predictors of pCR. Hormone receptor-positive status and pCR were independent prognostic factors for better EFS, while hormone receptor-positive status was the only independent prognostic factor for better OS.

BRAF Expression and Copy Number Alterations Predict Unfavorable Tumor Features and Adverse Outcomes in Patients With Breast Cancer.

Background: The role of BRAF in breast cancer pathogenesis is still unclear. To address this knowledge gap, this study is aimed at evaluating the impact of BRAF gene expression and copy number alterations (CNAs) on clinicopathologic characteristics and survival in patients with breast cancer. Methods: The Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) dataset was obtained from the cBioPortal public domain. Tumoral BRAF mRNA expression and CNAs along with demographic and tumor data for patients with breast cancer were retrieved. The association of BRAF expression and CNAs with breast cancer clinicopathologic characteristics was analyzed. The impact of BRAF mRNA expression on the overall survival of patients was assessed using Kaplan-Meier survival analysis. Results: BRAF gene mRNA log intensity expression was positively correlated with tumor size and the Nottingham Prognostic Index (NPI) (p < 0.001). Alternatively, BRAF gene expression was negatively correlated with the age at diagnosis (p = 0.003). The average BRAF mRNA expression was significantly higher in premenopausal patients, patients with high tumor grade, hormone receptor-negative status, and non-luminal tumors compared to postmenopausal patients, patients with low-grade, hormone receptor-positive, and luminal disease. BRAF gain and high-level amplification copy numbers were significantly associated with higher NPI scores and larger tumor sizes compared to neutral copy number status. Survival analysis revealed no discernible differences in overall survival for patients with low and high BRAF mRNA expression. Conclusion: High BRAF mRNA expression as well as the gain and high-level amplification copy numbers were associated with advanced tumor characteristics and unfavorable prognostic factors in breast cancer. BRAF could be an appealing target for the treatment of premenopausal patients with hormone receptor-negative breast cancer.

Skeletne metastaze karcinoma dojke - uticaj hormonskih i receptora humanog epidermalnog faktora rasta 2

Breast cancer is the leading cause of cancer-related deaths among women worldwide. While significant progress has been made in the prophylaxis, diagnosis, and management of breast cancer, around 90% of deaths occur due to metastatic disease, which is still incurable. The bone has been identified as one of the predominant metastatic sites, accounting for around 80% of patients with metastatic breast cancer. The paper aims to summarize the hallmarks of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) influence on breast cancer bone metastases development and their further biological and clinical behavior. Various clinicopathological characteristics have been identified as risk factors for the development of metastases. In particular, the status of ER, PR and HER2 is crucial for making clinical decisions as an important tool for predicting the spread of breast cancer and choosing a therapeutic protocol. Patients with any hormone receptor-positive status, particularly those with ER+, PR+/HER2-, are more likely to develop bone-only-metastatic (BOM), whereas those with hormone receptor-negative status, especially those with so-called triple-negative (HR-/HER2-) or HER2+ breast cancer, have a predilection for visceral metastases. The paper highlights that while bone metastases of breast cancer are much less investigated than primary tumors, more studies are needed to understand the complex, multi-step process involved in the development and behavior of bone metastases.

Evolution and prognostic significance of HER-2 conversion from primary to residual disease in HER-2 negative patients with breast cancer after neoadjuvant chemotherapy.

This study aimed to analyze HER-2 zero or HER-2 low conversion in HER-2 negative patients after neoadjuvant chemotherapy (NAC) and evaluate its prognostic significance. HER-2 negative patients with breast cancer with residual disease after NAC and paired pre- and post-therapeutic HER-2 testing results were analyzed retrospectively. HER-2 low, defined as immunohistochemistry (IHC) scores of 1+ or 2+/in situ hybridization (ISH), were not amplified. HER-2 zero is defined as an IHC score of 0. A total of 571 patients were enrolled, including primary HER-2 zero (n=201, 35.2%) and HER-2 low (n=370, 64.8%). The overall HER-2 change rate was 32.4%. Multivariable logistic regression showed that patients with hormone receptor-positive status before NAC was significantly associated with the conversion of HER-2 zero to low (OR=3.436, P < 0.0001). The median follow-up time was 50.0 months. In patients who are primary HER-2 zero, HER-2 zero to low was significantly associated with better disease-free survival (DFS) than constant HER-2 zero (HR=0.49, P=0.01) after adjustment (4-year DFS 80.1% vs 55.7%, Log-rank P=0.033). Subgroup analysis revealed that among patients who are primary HER-2 zero with hormone receptor-positive, HER-2 zero to low had a significantly better DFS than constant HER-2 zero (Log-rank P=0.037). In contrast, patients with hormone receptor-negative status did not. In conclusion, almost one-third of patients who are HER-2 negative underwent HER-2 zero or HER-2 low conversion after NAC. HER-2 zero to low conversion was associated with better DFS in patients who are HER-2 zero. These results provide a valuable reference for the potential application of anti-HER-2 ADC in an adjuvant setting for patients with residual disease after NAC.

Endometrial pathologies in clinical follow-up of patients with hormone receptor-positive/negative breast cancer

Background/Aim: Breast cancer is the leading cause of cancer-related fatalities in women. Tamoxifen, a selective estrogen receptor modulator (SERM), is frequently employed for chemoprevention in hormone receptor (HR)-positive breast cancer patients due to its anti-estrogenic impact on breast tissue. Nevertheless, tamoxifen exhibits agonistic effects on the endometrium, particularly in postmenopausal women. This study aims to assess gynecological issues and endometrial pathologies that emerge during the treatment and follow-up phases of women diagnosed with HR-positive/negative breast cancer. Methods: This cohort study involved a data review from 857 breast cancer patients diagnosed over a decade at a tertiary center. Histopathological endometrial findings were evaluated for 166 patients who underwent gynecological consultations before breast cancer treatment with normal examination results and underwent invasive assessments due to gynecological symptoms that arose during treatment and follow-up. The study encompassed cases culminating in total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH+BSO). Results: The study analyzed 166 cases meeting the inclusion criteria. The mean age at breast cancer diagnosis was 48 years with a standard deviation of 8.4 years, and the average follow-up duration was 4.1 (3.8) years. The predominant histopathological type was invasive ductal carcinoma (75.3%). Of the cases, 68.6% occurred during premenopausal and 31.4% during postmenopause. HR positivity was identified in 136 cases (81.9%), while 30 (18.1%) exhibited negative HR status. Among HR-positive cases, 113 (83.0%) received tamoxifen treatment, while 23 (17.0%) were treated with letrozole. Common clinical findings during and after treatment encompassed increased endometrial thickness (ET) and abnormal uterine bleeding (AUB). Histopathological evaluation of invasive procedures prompted by increased ET indicated the following frequent endometrial findings: proliferative endometrium (33.1%), endometrial polyp (20.5%), and endometrial hyperplasia (EH) without atypia (9%). The histopathological outcomes of invasive procedures prompted by AUB included atrophic endometrium (11.4%), proliferative endometrium (3.6%), and endometrial cancer (1.8%). Among the endometrial malignancies, three occurred in the premenopausal phase and four in the postmenopausal phase. Notably, three of the seven endometrial malignancies were observed in the tamoxifen hormone therapy group, all HR-positive. Four cases were from the non-tamoxifen hormone therapy group with negative HR status. Conclusion: Globally, breast cancer ranks as the most prevalent malignancy in women. Tamoxifen, a frequently utilized adjuvant therapy post breast cancer surgery, can exert diverse effects on gynecological organs, encompassing benign pathologies like increased ET and malignant pathologies like uterine neoplasia. There is a rising suspicion that etiopathogenetic factors contributing to breast cancer progression might also precipitate uterine cancer, irrespective of tamoxifen use. Vigilant patient monitoring is paramount for detecting uterine neoplasia and other gynecological pathologies.

Association of clinicopathologic and molecular factors with the occurrence of positive margins in breast cancer

PurposeTo explore the association of clinicopathologic and molecular factors with the occurrence of positive margins after first surgery in breast cancer.MethodsThe clinical and RNA-Seq data for 951 (75 positive and 876 negative margins) primary breast cancer patients from The Cancer Genome Atlas (TCGA) were used. The role of each clinicopathologic factor for margin prediction and also their impact on survival were evaluated using logistic regression, Fisher’s exact test, and Cox proportional hazards regression models. In addition, differential expression analysis on a matched dataset (71 positive and 71 negative margins) was performed using Deseq2 and LASSO regression.ResultsAssociation studies showed that higher stage, larger tumor size (T), positive lymph nodes (N), and presence of distant metastasis (M) significantly contributed (p ≤ 0.05) to positive surgical margins. In case of surgery, lumpectomy was significantly associated with positive margin compared to mastectomy. Moreover, PAM50 Luminal A subtype had higher chance of positive margin resection compared to Basal-like subtype. Survival models demonstrated that positive margin status along with higher stage, higher TNM, and negative hormone receptor status was significant for disease progression. We also found that margin status might be a surrogate of tumor stage. In addition, 29 genes that could be potential positive margin predictors and 8 pathways were identified from molecular data analysis.ConclusionThe occurrence of positive margins after surgery was associated with various clinical factors, similar to the findings reported in earlier studies. In addition, we found that the PAM50 intrinsic subtype Luminal A has more chance of obtaining positive margins compared to Basal type. As the first effort to pursue molecular understanding of the margin status, a gene panel of 29 genes including 17 protein-coding genes was also identified for potential prediction of the margin status which needs to be validated using a larger sample set.

Helical Tomotherapy of Lymph Node-negative Early-stage Breast Cancer After Breast-conserving Surgery: Long-term Results.

Adjuvant radiotherapy is an integral part of the interdisciplinary curative treatment of breast cancer. We aimed to examine the long-term clinical results of helical tomotherapy in female patients with local restricted, lymph node negative breast cancer after breast-conserving surgery. In this single-centre analysis, 219 female patients with early-stage breast cancer (T1/2) and no lymph node metastasis (N0) following breast-conserving surgery and sentinel-node biopsy were treated with adjuvant fractionated whole breast radiation therapy using helical tomotherapy. When boost irradiation was indicated, it was administered sequentially or using the simultaneous-integrated boost technique. Local control (LC), metastasis and survival rates, acute toxicity, late toxicity, and secondary malignancy rates were analysed retrospectively. The mean follow-up time was 71 months. The 5- and 8-year overall survival (OS) rates were 97.7% and 92.1%, respectively. The 5- and 8-year LC rates were 99.5% and 98.2%, while the 5- and 8-year metastasis-free survival (MFS) rates of 97.4% and 94.3%, respectively. Patients with G3 grading or negative hormone receptor status did not show significantly different results. Acute erythema occurred in 79% (grade 0-2) and 21% (grade 3) of the patients. Lymphedema of the ipsilateral arm and pneumonitis occurred in 6.4% and 1.8% of the treated patients. None of the patients developed >grade 3 toxicities during follow-up, while 1.8% developed a secondary malignancy during follow-up. Helical tomotherapy showed excellent long-term results and low toxicity rates. The incidence rates of secondary malignancy were relatively low and correlated with pre-existing data on radiotherapy, suggesting wider implementation of helical tomotherapy in adjuvant radiotherapy for breast cancer patients.

Abstract P4-02-16: Prognostic and Predictive Capacity of Tumor Infiltrating Lymphocytes in the MA.20 regional radiotherapy trial

Abstract Background: The benefit of regional nodal irradiation (RNI) in patients with low burden metastatic axillary disease was established in MA.20 showing that patients randomized to receive adjuvant whole breast irradiation (WBI) plus RNI experienced a significantly better disease free survival (DFS) and distant disease free survival (DDFS) compared to those who received WBI alone and this advantage was maintained in the hormone receptor negative subgroup. Stromal tumor infiltrating lymphocytes (sTILs) have shown prognostic and predictive value in HER2 positive and triple negative breast cancers. To date, clinical importance of immune infiltrates as prognostic and predictive biomarkers in the context of benefit from RNI has not been shown. Methods: 1064 full-face hematoxylin and eosin (H&amp;E) stained sections and formalin fixed paraffin embedded primary tumor blocks assembled into 16 tissue microarrays (TMAs) in quadruplicates linked with clinical data were accessible from the original 1832 patients in the MA.20 trial for this retrospective-prospective translational study conducted according to the REMARK guidelines. sTILs were assessed on scanned images of H&amp;E sections according to the International Immuno-Oncology Working Group method, and on TMAs by CD8 immunohistochemistry (IHC) using a validated assay. Biomarkers were scored by pathologists blinded to the clinical data and analyzed as continuous and categorical variables using prespecified median cutpoints. The median follow-up was 9.5 years. Cox proportional regression modelling was used after adjusting for clinicopathological factors and treatments. Hazard ratios (HR) with 95% confidence intervals (CI) were reported for the primary endpoint of DFS and secondary endpoint of DDFS. Predictive value was assessed by the interaction test between the treatment arm and the biomarkers in the full cohort and an IHC defined non-luminal A subgroup. Results: 1035 cases were evaluable for sTILs on H&amp;E sections. Of these 52.6% (n=544) cases with ≥10% sTILs displayed a significant correlation with age &amp;lt; 50 years, grade III, tumor size &amp;gt;2cm, hormone receptor negative status, and non-luminal A subgroup (p &amp;lt; 0.05). Of the 857 evaluable cases on TMAs, CD8+sTILs (≥16) were observed in 49.8% (n=427) cases and showed a significant association with grade III, ER negativity and non-luminal A status (p &amp;lt; 0.05). For the full cohort, H&amp;E sTILs assessed as a continuous parameter, were not prognostic for DFS (HR 0.993; 95% CI 0.984-1.003; p=0.18) but provided prognostic information for DDFS (HR 0.988; 95% CI 0.977-0.999; p=0.04) in multivariate analyses. H&amp;E sTILs did not show predictive value as a continuous variable. Similarly, using the prespecified cutpoint (≥10%), H&amp;E sTILs were neither prognostic nor predictive. Increasing level of CD8+sTILs was associated with significantly improved DFS (HR 0.99; 95% CI 0.983-0.998; p=0.02) and DDFS (HR 0.98; 95% CI 0.97-0.99; p=0.002) in multivariate analyses. For the full cohort, CD8+sTILs as a continuous variable, showed a significant improvement in DDFS for patients randomized to WBI and RNI (HR 0.979; 95%CI 0.959-0.999; p(interaction) =0.04) compared to WBI alone and a trend (HR 0.977; 95%CI 0.954-1.001; p(interaction) =0.06) for better outcome was observed for the non-luminal A subgroup. CD8+sTILs at the prespecified cutpoint (≥16) were not prognostic or predictive. Conclusions: Pre-treatment tumoral infiltration with stromal lymphocytes provided positive prognostic information for DFS (CD8+sTILs) and DDFS (H&amp;E sTILs and CD8+sTILs) when examined as a continuous variable but failed to do so at prespecified cutpoints. While CD8+sTILs as a continuous variable predicted benefit from RNI, significant prediction results were not seen for prespecified cutpoint or related biomarker H&amp;E sTIL. These results require further validation. Citation Format: Nazia Riaz, Bingshu Chen, Anita Bane, Dongxia Gao, Elisabeth Stovgaard, Zuzana Kos, Samuel Leung, Elahe Shenasa, Wendy Parulekar, Shelley Chambers, Torsten Nielson, Timothy J. Whelan. Prognostic and Predictive Capacity of Tumor Infiltrating Lymphocytes in the MA.20 regional radiotherapy trial [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-02-16.

Abstract P5-07-01: Outcomes of multidisciplinary team approach and intensive patient education in young women with breast cancer to improve the rate of fertility preservation

Abstract Background Young breast cancer patients of childbearing age often had to give up their opportunity as women or mothers for cancer treatment. As the survival rate of young breast cancer patients increases with advances in early detection and treatment of breast cancer, interest in issues such as fertility preservation, which have not been satisfied so far, is increasing. This study aims to report the experience of improvement of the fertility preservation rate through a multidisciplinary team approach and systematic patient education for young breast cancer patients. Methods Patients treated with multidisciplinary team approach including surgical, medical oncologist and fertility specialist were included for analysis. Patient were divided into two periods: before and after intensive patient education. Patient education included in-person counseling, hand-out materials, and audiovisual education about ovarian dysfunctions related to cancer treatment and fertility preservation methods. We compared the rate of fertility counseling, preservation between two periods. Also, effect of hormonal receptor status on fertility outcome with pregnancy and birth were analyzed. Results The rates of fertility counseling (39.4% to 58.1%), ovarian function preservation with gonadotropin releasing hormone antagonists (37.8% to 49.7%), and either embryo (0.9% to 5.6%) or oocyte preservation (0 to 7.5%) were significantly increased (all, p&amp;lt; 0.001) after intensive patient education. Pregnancy (9.5% vs 14.2%, p=0.034) and birth rate (7.7% vs 12.2%, p=0.043) were significantly higher with women with negative hormone receptor status. In hormone receptor positive patients, similar pregnancy rates were observed (13.3 ~ 15.4%) in patients who complete 5yearsd of endocrine therapy, stopped endocrine therapy due to side effects, and received no endocrine therapy. Patients with any type of recurrence were not pregnant during follow up period. Patients who stopped endocrine therapy for child plan showed highest rate of pregnancy (56.0%). Multivariable analysis revealed intensive education were highly associated with improved fertility outcomes (OR 3.843 95% CI 2.781–5.311, p=&amp;lt; 0.001) after adjusted for different stage and treatment modality. Conclusion Multidisciplinary team approach with intensive patient education of fertility preservation in young women breast cancer significantly improved fertility preservation attempt. Hormonal receptor status and recurrence were associated with impaired fertility outcomes Citation Format: Young Joo Lee, Hayan Han, Hee Jeong Kim. Outcomes of multidisciplinary team approach and intensive patient education in young women with breast cancer to improve the rate of fertility preservation [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-07-01.

Abstract P2-17-03: Preclinical study of trastuzumab deruxtecan (T-Dxd; DS-8201a) in combination with DNA damage response pathway inhibitors in HER2-low/Hormone receptor negative breast cancer patient-derived xenograft models

Abstract Background: Triple negative breast cancer (TNBC), defined by negative hormone receptor (HR) status and the lack of HER2 gene amplification, is a significant clinical challenge because of its aggressive clinical course and association with a poor prognosis. Recent studies demonstrated that approximately a third of TNBC has low expression of HER2, so called HER2-low TNBC, which could be targeted by the new generation HER2-directed antibody-drug conjugate (ADC). Trastuzumab deruxtecan (also known as T-Dxd, DS-8201a) is a novel HER2-directed ADC with a topoisomerase 1 inhibitor payload and a tetrapeptide-based cleavable linker, which has been FDA approved for patients with metastatic HER2-positive, or amplified breast cancer. T-Dxd has also shown to improve survival outcomes when compared to physicians’ choice chemotherapy in patients with metastatic HR-negative/HER2-low breast cancer in the Phase 3 DESTINY-Breast04 trial. However, resistance is invariable. We hypothesize that small molecule inhibitors against DNA damage response (DDR) pathways could potentiate the DNA damaging effect of T-Dxd and improve its anti-tumor activity in HER2-low TNBC. Method: We conducted preclinical experiments to assess the anti-tumor activity of T-Dxd and each of the DDR pathway inhibitors, including the ATR inhibitor AZD6738, the ATM inhibitor AZD1390, and the PARP inhibitor olaparib, as well as the Wee 1 inhibitor AZD1775, either alone or in combination, compared to the vehicle treatment, in a panel of HER2-low TNBC PDX models in vivo, as well as mechanistic studies using HER2-low TNBC cell lines in vitro. HER2-low was defined as 1+ or 2+ on HER2 immunohistochemistry. Results: Four HER2-low TNBC PDX models, including WHIM2 (TP53 mutated, basal-like), WHIM6 (TP53 WT, basal-like), WHIM12 (TP53, PIK3CA, and PTEN mutated, claudin-low), and WHIM30 (BRCA1 and TP53 mutated, basal-like), as well as a panel of 4 TNBC cell lines with variable HER2 expression were included in the study. We demonstrated that the addition of DDR pathway inhibitors to T-Dxd led to further tumor shrinkage and delayed tumor progression in HER2-low TNBC PDX models in vivo and induced synergistic anti-tumor effects in vitro. Enhanced DNA damaging effect and apoptosis induction were observed with combination therapies in vitro. Biomarker analysis on xenograft tumors harvested 3 days following treatment with either Vehicle, T-Dxd, olaparib, or T-Dxd plus olaparib in WHIM6, was also performed, which demonstrated that the addition of olaparib enhanced DNA damage (increased pH2AX), and promoted apoptosis (increased cleaved PARP). Further mechanistic studies in HER2-low TNBC cell lines demonstrated the formation of DNA topoisomerase 1 covalent complexes (TopoIcc) following treatment with T-Dxd. Interestingly, while the formation of Topolcc was reduced with the addition of either ATR or ATM inhibitor, no reduction was observed with the addition of olaparib. Additionally, we observed that combination therapies reduced cell migration in vitro. The combination of olaparib with T-Dxd, in particular, reduced mammosphere formation and Epithelial Mesenchymal Transition (EMT) modulation markers, including SNAIL, SLUG and/or TWIST. Conclusion: Our study demonstrated that the combination of T-Dxd and DDR pathway inhibitors induced additive or synergistic anti-tumor effect in HER2-low TNBC. Our data from the studies of cell lines and PDX models provided preclinical rationale for the combination of T-Dxd and DDR pathway inhibitors in patients with HER2-low TNBC. The olaparib combination showed unique mechanistic characteristics compared with other DDR inhibitors, which are being further examined in additional HER2-low TNBC models. Citation Format: Adrian Gonzalez-Gonzalez, Zhanfang Guo, Alice Meroni, Emily Cybulla, Jeremy Hoog, Alessandro Vindigni, Cynthia Ma. Preclinical study of trastuzumab deruxtecan (T-Dxd; DS-8201a) in combination with DNA damage response pathway inhibitors in HER2-low/Hormone receptor negative breast cancer patient-derived xenograft models [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-17-03.

Carbonic Anhydrase IX in Tumor Tissue and Plasma of Breast Cancer Patients: Reliable Biomarker of Hypoxia and Prognosis

Carbonic anhydrase IX (CA IX) is recognized as an excellent marker of hypoxia and an adverse prognostic factor in solid tumors, including breast cancer (BC). Clinical studies confirm that soluble CA IX (sCA IX), shed into body fluids, predicts the response to some therapeutics. However, CA IX is not included in clinical practice guidelines, possibly due to a lack of validated diagnostic tools. Here, we present two novel diagnostic tools-a monoclonal antibody for CA IX detection by immunohistochemistry and an ELISA kit for the detection of sCA IX in the plasma-validated on a cohort of 100 patients with early BC. We confirm that tissue CA IX positivity (24%) correlates with tumor grading, necrosis, negative hormone receptor status, and the TNBC molecular subtype. We show that antibody IV/18 can specifically detect all subcellular forms of CA IX. Our ELISA test provides 70% sensitivity and 90% specificity. Although we showed that this test could detect exosomes in addition to shed CA IX ectodomain, we could not demonstrate a clear association of sCA IX with prognosis. Our results indicate that the amount of sCA IX depends on subcellular CA IX localization, but more strictly on the molecular composition of individual molecular subtypes of BC, particularly on metalloproteinases inhibitor expression.