Primary Tumor HER2 Status Research Articles

Abstract 3758: Evaluation of breast cancer-derived extracellular vesicles as diagnostic indicator for HER2 status

Abstract HER2-low is a new distinct type of breast cancer that is characterized by low levels of the HER2 protein. As treatment paradigms for HER2-low breast cancer are rapidly evolving with the approval of antibody-drug conjugates, identification of HER2-low breast cancer with more sensitive and reproducible HER2 assays is needed. We aimed to investigate the utility of liquid biopsy in isolating tumor-derived extracellular vesicles (TDEs) for diagnosis of HER2 status. We adopted an affinity-based approach to isolate TDEs and performed CNV analysis of the ERBB2/neu genes using the tumor DNA present in TDEs (etDNA). HER2 status of etDNA had been determined by droplet digital PCR using HER2/EIF2C ratio, a highly accurate method to quantify DNA copy number. In our study, we utilized a variety of breast cancer cell lines categorized as HER2-low (MDA-MB-231, MCF7, ZR-75-1) and HER2-high (MDA-MB-453, BT-474, SK-BR-3) to confirm HER2 expression in extracellular vesicles (EVs) by flow cytometry. This analysis successfully demonstrated that EVs effectively reflect the HER2 status of the tumor cells, evidenced by a strong Pearson correlation coefficient (r=0.987, p<0.001). Further clinical validation was conducted with plasma samples from 22 breast cancer patients. In the clinical study, we observed a significant correlation between the CNV of tumor DNA present in TDEs and the HER2 status of primary tumors (p<0.01). Additionally, the Receiver Operating Characteristic (ROC) analysis yielded an impressive area under the curve (AUC) value of 0.838 (p<0.01), demonstrating a high level of accuracy in differentiating between high and low HER2 groups, with a sensitivity of 55.6% and a specificity of 100%. In summary, we show potential diagnostic tools for real-time, less invasive determination of HER2 status in primary tumors, providing continuous monitoring methods for HER2 status. Although further validation in larger cohorts and prospective studies is needed, our study indicates that TDE analysis could contribute to the assays for identification of the HER2 status in breast cancer patients. Citation Format: Sol Moon, Min Woo Kim, Young Kim, Suji Lee, Hyojung Lee, Joon Ye Kim, Seung Il Kim, Jee Ye Kim. Evaluation of breast cancer-derived extracellular vesicles as diagnostic indicator for HER2 status [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3758.

HER2-low metastases of HER2-negative primary tumors: a single institution analysis of intertumoral and internodal heterogeneity in node-positive breast cancer.

HER2 status in breast cancer is an essential parameter in individual therapeutic decision-making and is routinely assessed in primary tumors in accordance with international recommendations. Reports of HER2 heterogeneity raise the question of basing treatment decisions on HER2 status in metastases, if present. We investigated the degree and clinical implications of HER2 heterogeneity in lymph node-positive breast cancer. Because of recent recognition of therapeutic opportunities in this group of tumors, we especially focused on cases involving low-level HER2 expression. The HER2 status of primary tumors and of corresponding lymph node metastases was determined in archived material at the protein and gene levels using the gene- protein assay and interpreted in accordance with 2018 ASCO/CAP criteria. HER2-low status was defined as protein expression levels 1+ or 2+ with negative amplification status. We analyzed a series of 43 cases of primary infiltrating breast cancer, each with at least two axillary nodes harboring macrometastases (>2 mm), in total 206 such nodes. In 7% of cases, we detected intertumoral HER2 heterogeneity. Three of nine HER2-positive primary tumors were associated with HER2-negative metastases. No cases with HER2-negative primary tumors had HER2-positive metastases, but 55% (6/11) of HER2 0 primary tumors had HER2 1+ and/or 2+ metastases, and 19% (3/16) HER2 1+ cases had exclusively HER2 0 metastases. All metastases in HER2 2+ cases showed HER2-low protein expression levels. Internodal HER2 heterogeneity at low protein expression levels (presence of HER2 0, HER2 1+, and/or HER2 2+ metastatic deposits within the same axilla) was seen in 40% (17/43) of cases. We found no statistically significant association between HER2 heterogeneity and other tumor-related parameters. Survival data indicated worse outcomes in the HER2-low group compared with the rest of the cohort. Our results indicate a substantial instability of HER2 protein expression, leading to considerable intertumoral and internodal HER2 heterogeneity in lymph node-positive breast carcinomas. This heterogeneity is particularly relevant in HER2-low tumors in which the corrective effects of HER2 gene copy number analysis definitionally is absent. Our findings suggest that determining HER2 status in metastatic lymph nodes may generate relevant information for therapeutic decision-making.

Discordance of HER2-Low between Primary Tumors and Matched Distant Metastases in Breast Cancer.

We examined differences in HER2 expression between primary tumors and distant metastases, particularly within the HER2-negative primary breast cancer cohort (HER2-low and HER2-zero). The retrospective study included 191 consecutive paired samples of primary breast cancer and distant metastases diagnosed between 1995 and 2019. HER2-negative samples were divided into HER2-zero (immunohistochemistry [IHC] score 0) and HER2-low (IHC score 1+ or 2+/in situ hybridization [ISH]-negative). The main objective was to analyze the discordance rate between matched primary and metastatic samples, focusing on the site of distant metastasis, molecular subtype, and de novo metastatic breast cancer. The relationship was determined by cross-tabulation and calculation of Cohen's Kappa coefficient. The final study cohort included 148 paired samples. The largest proportion in the HER2-negative cohort was HER2-low [primary tumor 61.4% (n = 78), metastatic samples 73.5% (n = 86)]. The discordance rate between the HER2 status of primary tumors and corresponding distant metastases was 49.6% (n = 63) (Kappa -0.003, 95%CI -0.15-0.15). Development of a HER2-low phenotype occurred most frequently (n = 52, 40.9%), mostly with a switch from HER2-zero to HER2-low (n = 34, 26.8%). Relevant HER2 discordance rates were observed between different metastatic sites and molecular subtypes. Primary metastatic breast cancer had a significantly lower HER2 discordance rate than secondary metastatic breast cancer [30.2% (Kappa 0.48, 95%CI 0.27-0.69) versus 50.5% (Kappa 0.14, 95% CI -0.03-0.32)]. This highlights the importance of evaluating potentially therapy-relevant discordance rates between a primary tumor and corresponding distant metastases.

1142P - The Concordance of Her2 Status in Primary and Metastatic Sites of Extramammary Paget's Disease

ABSTRACT Background HER2-targeted therapies have been introduced to treat breast and stomach cancers that show HER2 protein overexpression and/or HER2 gene amplification. However, the HER2 status of primary tumors and their corresponding metastatic sites is shown to be heterogeneous in less than 20% of cases. In extramammary Paget's disease (EMPD), HER2 protein overexpression and gene amplification has been shown to occur in 5-80% of cases; however, knowledge regarding the concordance of HER2 status in primary and metastatic sites of EMPD is limited. The aim of this study was to clarify the concordance rate of HER2 status in the primary tumors and metastatic sites of EMPD. Methods Twenty-six tissue blocks of primary tumors and corresponding lymph node metastases were subjected to an immunohistochemistry (IHC) analysis. The IHC scores were classified into four groups (0 to 3+) according to the American Society of Clinical Oncology/College of American Pathologists Guidelines (2007). When the primary tumors and lymph node metastases showed IHC scores of either 2+ or 3 + , the presence of HER2 gene amplification was examined using fluorescence in situ hybridization (FISH) and dual-colored in situ hybridization (DISH). Results mmunohistochemically, 27% (7/26) of the primary tumors and 38% (10/26) of the lymph node metastases showed IHC scores of either 2+ or 3+. When HER2 protein overexpression was classified as being either positive (2 + , 3+) or negative (0, 1+), the concordance rate of the HER2 status of the primary tumors and corresponding lymph node metastases was 85% (22/26). The presence of HER2 gene amplification was examined in six primary tumors and 10 metastatic sites. HER2 gene was amplified in a total of seven cases (27%): four cases in both the primary and metastatic sites, two cases in the metastatic sites only and one case in the primary site only. Conclusion Good concordance of HER2 protein overexpression and gene amplification status was seen in the primary tumors and corresponding lymph node metastases of patients with EMPD. Furthermore, the HER2 gene was found to be always amplified in cases with an IHC score of 3+ and in two cases with an IHC score of 2+ in the lymph node metastases, which is suitable to be targeted for therapy. Disclosure All authors have declared no conflicts of interest.

PD05-05: Meta Analysis of Discordant HER2 Status in Matched Primary and Metastatic Breast Cancer.

Abstract Background: The status of HER2 amplification in breast cancer is an important prognostic and predictive indicator. Only those tumors exhibiting HER2 overamplification are candidates for HER2 targeted therapy. It remains controversial how accurately HER2 status of primary tumors reflects HER2 status in distant metastases. Discordance between primary and metastatic tumors can impact significantly on patient management and suitability for HER2 targeted therapies in the setting of recurrent distant disease. Methods: A literature search of the PubMed database was performed to identify all primary studies comparing HER2 status in matched primary and distant metastatic tumors between January 2005 and February 2011. Review and data extraction was performed by two independent reviewers. Eligible studies evaluated HER2 status by current ASCO guidelines. Studies comparing paired primary and axillary lymph nodes or synchronous primaries and metastases were excluded. Weighted pooled estimates were calculated. Results: The original search strategy retrieved 1703 studies for which there were 62 eligible studies for full evaluation. Metastatic sites included bone, brain, lung and liver. Traztuzumab was received in three studies. Weighted summary estimate for negative to positive discordance was 23% (95% CI, 16.0-28%). Positive to negative discordance had a weighted summary estimate of 4% (95% CI, 0.0-6%). Discussion: Meta analysis of studies adhering to ASCO guidelines for HER2 status determination revealed a significant rate of change to HER2 positive metastatic disease in HER2 unamplified primary breast cancers. This data suggests that nearly one quarter of patients may be denied the benefit of HER2 targeted therapy if HER2 primary status alone is used a the sole measure in determining therapeutic options upon distant recurrence. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD05-05.

HER2 Status in Ovarian Carcinomas: A Multicenter GINECO Study of 320 Patients

BackgroundDespite a typically good response to first-line combination chemotherapy, the prognosis for patients with advanced ovarian cancer remains poor because of acquired chemoresistance. The use of targeted therapies such as trastuzumab may potentially improve outcomes for patients with ovarian cancer. HER2 overexpression/amplification has been reported in ovarian cancer, but the exact percentage of HER2-positive tumors varies widely in the literature. In this study, HER2 gene status was evaluated in a large, multicentric series of 320 patients with advanced ovarian cancer, including 243 patients enrolled in a multicenter prospective clinical trial of paclitaxel/carboplatin-based chemotherapy.Methodology/Principal FindingsThe HER2 status of primary tumors and metastases was evaluated by both immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) analysis of paraffin-embedded tissue on conventional slides. The prognostic impact of HER2 expression was analyzed. HER2 gene was overexpressed and amplified in 6.6% of analyzed tumors. Despite frequent intratumoral heterogeneity, no statistically significant difference was detected between primary tumors and corresponding metastases.Conclusions/SignificanceOur results show that the decision algorithm usually used in breast cancer (IHC as a screening test, with equivocal results confirmed by FISH) is appropriate in ovarian cancer. In contrast to previous series, HER2-positive status did not influence outcome in the present study, possibly due to the fact that patients in our study received paclitaxel/carboplatin-based chemotherapy. This raises the question of whether HER2 status and paclitaxel sensitively are linked.

Role of HER2 in local relapse and metastasis

HER2-positive breast carcinomas have been shown to display an early peak of relapses in the first 4 years after surgery, especially in the node-positive subgroup. To explain this observation, growth factors released at the time of surgery were investigated. The level of growth factors of the EGF family, detected in postsurgical sera from breast carcinoma patients, was found to correlate with surgical invasiveness. Indeed, following radical mastectomy, higher levels of serum EGF-like factors were found than after conservative surgery. This implicates that the growth of tumors overexpressing HER2, activated by these growth factors, should be stimulated after invasive surgery. Two retrospective analyses of the HER2 status of primary tumors included in a randomized clinical trial addressing the issue of conservative versus invasive surgery and of radiotherapy were performed by immunohistochemistry using the standardized herceptest. Survival analysis according to surgery indicated no differences in HER2-negative cases but indicated a poorer survival for HER2-positive node-positive patients who had mastectomy in comparison with those who had conservative surgery. Furthermore, local relapses in patients who had conservative surgery without radiotherapy were found to be anticipated in the HER2-positive subset. This is a 'proof of principle' that surgery by inducing growth factor release may be detrimental for patients with HER2-positive tumors. To verify these findings, a prospective analysis of the follow-up of more than 2000 patients who have had mastectomy or conservative surgery is ongoing. Preliminary data indicate a significantly worst prognosis of HER2-positive tumors after invasive surgery, above all for tumors scoring 2+ by immunohistochemistry.