HER2 Gene Amplification Research Articles

148P DESTINY-PanTumor02 study of trastuzumab deruxtecan (T-DXd) in patients (pts) with HER2-expressing solid tumors: Exploratory biomarker analyses of HER2 expression and gene amplification in tissue and plasma

148P DESTINY-PanTumor02 study of trastuzumab deruxtecan (T-DXd) in patients (pts) with HER2-expressing solid tumors: Exploratory biomarker analyses of HER2 expression and gene amplification in tissue and plasma

Clinicopathological features and differential diagnosis of gastric pleomorphic giant cell carcinoma.

The aim of this study was to investigate the clinicopathological features and differential diagnosis of gastric pleomorphic giant cell carcinoma. Histopathology, immunohistochemistry, and human epidermal growth factor receptor 2 (HER2) gene testing were conducted for seven cases of gastric pleomorphic giant cell carcinoma. In histomorphological terms, all seven cases involved pleomorphic giant cell carcinoma, accounting for more than 10% of the entire tumor, with pleomorphic spindle cells and giant cells mixed with various histomorphological structures of adenocarcinoma with high, intermediate, and low differentiation. There was large heterogeneity in the HER2 protein expression and HER2 gene amplification in the gastric pleomorphic giant cell carcinoma, and both levels of HER2 were focal in three cases, accounting for 42.9% (3/7). The mismatch repair gene proteins MLH1, MSH2, PMS2, and MSH6 were positive. Routine immunohistochemical markers, i.e., pan-cytokeratin, epithelial membrane antigen, villin, caudal-type homeobox 2, E-cadherin, and p53, were positive in the gastric pleomorphic giant cell carcinoma, while vimentin, calponin, smooth muscle actin, nestin, S-100, cluster of differentiation (CD) 99, desmin, and CD34 were focally expressed in both the spindle and the giant cells, with Ki-67-positive cells accounting for 70-80%. Gastric pleomorphic giant cell carcinoma presents multiple histomorphological features and is easily confused with various tumors. Clarifying the histopathological features of this type of tumor is important for differential diagnosis and precise treatment.

HER2-low expression in patients with advanced or metastatic solid tumors

Human epidermal growth factor receptor 2 (HER2)-low is a newly defined category with HER2 1+ or 2+ expression by immunohistochemistry (IHC) and lack of HER2 gene amplification measured by in situ hybridization (ISH). Much remains unknown about the HER2-low status across tumor types and changes in HER2 status between primary and metastatic samples. HER2 expression by IHC was evaluated in 4701 patients with solid tumors. We have evaluated the HER2 expression by IHC and amplification by ISH in paired breast and gastric/gastroesophageal (GEJ) primary and metastatic samples. HER2 expression was correlated with ERBB2 genomic alterations evaluated by next-generation sequencing (NGS) in non-breast, non-gastric/GEJ samples. HER2 expression (HER2 IHC 1-3+) was found in half (49.8%) of the cancers, with HER2-low (1 or 2+) found in many tumor types: 47.1% in breast, 34.6% in gastric/GEJ, 50.0% in salivary gland, 46.9% in lung, 46.5% in endometrial, 46% in urothelial, and 45.5% of gallbladder cancers. The concordance evaluation of HER2 expression between primary and metastatic breast cancer samples showed that HER2 3+ remained unchanged in 87.1% with a strong agreement between primary and metastatic samples, with a weighted kappa (Κ) of 0.85 (95% confidence interval 0.79-0.91). ERBB2 alterations were identified in 117 (7.5%) patients with non-breast, non-gastric/GEJ solid tumors who had NGS testing. Of 1436 patients without ERBB2 alterations, 512 (35.7%) showed any level HER2 expression by IHC. Our results show that HER2-low expression is frequently found across tumor types. These findings suggest that many patients with HER2-low solid tumors might benefit from HER2-targeted therapies.

Comparisons between HER2-low and HER2-zero tumors with 21-gene multigene assay in 2,295 ER+ HER2- breast cancer.

13 Background: HER2-positivity is an essential marker for therapeutic decisions, while HER2 expression is heterogenous. In recent years, there has been increasing recognition of a subgroup of breast cancer patients who have low levels of HER2 expression, also known as HER2-low because trastuzumab deruxtecan offers clinical benefit for patients with HER2-low metastatic breast cancer. Despite the growing interest in HER2-low breast cancer, there is limited research on how multigene assays can help differentiate between HER2-low and HER2-negative breast cancer. Among ER+HER2- breast cancer, we compared genomic characteristics between HER2-low and HER2-zero using the 21-gene assay. Methods: A retrospective review of clinical records was performed in 2,295 patients who underwent Oncotype DX test in two hospitals between 2013 and 2020. Patients were classified into two groups as the HER2-zero and HER2-low based on HER2 IHC and SISH test. In cases with HER2 2+, no amplification of HER2 gene was confirmed by silver in situ hybridization. High genomic risk was defined as cases with 21-gene recurrence score (RS)>25. Multivariable binary logistic-regression analysis was performed. Results: Of these, 944 (41.1%) were assigned in the HER2-zero, and 1351 (58.9%) were in the HER2-low. The averages of RS were 17.082 in the HER2-zero breast cancer and 18.503 in the HER2-low, respectively (P-value<0.005). HER2 score identified by qRT-PCR was 8.912 in the HER2 zero group and was 9.337 in the HER2 low group (P<0.005). When we compared a proportion of high RS between two groups, the high RS rate was 12.4% (117 of 944) in the HER2-zero, while it was 17.0% (230 of 1351) in the HER2-low (p=0.002). In multivariable analysis, HER2-low was demonstrated as an independent factor for high RS with an odds ratio 1.517 (1.172-1.964) independent of ER, PR, and Ki67. Within the subgroup with invasive ductal carcinoma, the high RS rates of HER2-low and HER2-zero were 19% and 14%, respectively. In the all patients, recurrence-free survival and overall survival did not differ between HER2-low and HER2-zero groups. Conclusions: Within ER+HER2- breast cancer, HER2-low tumors are associated with high RS, especially for histologically invasive ductal carcinoma. A prognostic influence of HER2-low expression among ER+HER2- breast cancer remains as an area that requires further study.

Recent Update of Targeted Therapy in Cholangiocarcinoma

Cholangiocarcinoma (CCA) is one of the cancers with the worst prognosis. Its incidence and mortality have increased in recent years, but treatment options are limited. Although various clinical trials have been conducted, there is no effective therapeutic agent yet. As molecular genetic profiling is progressing in CCA, the interest in targeted therapies is growing. To realize targeted therapy in practice, various clinical requirements must be met. A molecular biological test should be performed on a patient’s tissue or blood, a target should be determined using an appropriate analysis method, and there should be a targeted agent. Regarding CCA, genetic variation occupies an intermediate level. Accordingly, many new agents have been recently developed for molecular biological targets. The most common genetic aberrations show almost similar patterns in intrahepatic and extrahepatic CCA. However, HER2 gene amplification is more often observed in extrahepatic CCA, and FGFR2 fusion, IDH1 mutation, and RAS-RAF-MEK-ERK signaling system mutations are more frequently found in intrahepatic CCA. Phase 2 or 3 clinical trials are being conducted with zanidatamab for HER2 amplification, pemigatinib/infigratinib for FGFR fusion, ivosidenib for IDH1 mutation, and dabrafenib for BRAFV600E mutation. In addition, clinical trials for agents targeting the NTRK, BRCA, and ARID1A gene mutations are ongoing. These targeted therapies are expected to have a bright future as a new treatment for CCA.

Deep learning to automatically evaluate HER2 gene amplification status from fluorescence in situ hybridization images

Human epidermal growth factor receptor 2 (HER2) gene amplification helps identify breast cancer patients who may respond to targeted anti-HER2 therapy. This study aims to develop an automated method for quantifying HER2 fluorescence in situ hybridization (FISH) signals and improve the working efficiency of pathologists. An Aitrox artificial intelligence (AI) model based on deep learning was constructed, and a comparison between the AI model and traditional manual counting was performed. In total, 918 FISH images from 320 consecutive invasive breast cancers were analysed and automatically classified into 5 groups according to the 2018 ASCO/CAP guidelines. The overall classification accuracy was 85.33% (157/184) with a mean average precision of 0.735. In Group 5, the most common group, the consistency was as high as 95.90% (117/122), while the consistency was low in the other groups due to the limited number of cases. The causes of this inconsistency, including clustered HER2 signals, coarse CEP17 signals and some section quality problems, were analysed. The developed AI model is a reliable tool for evaluating HER2 amplification statuses, especially for breast cancer in Group 5; additional cases from multiple centres could further improve the accuracy achieved for other groups.

Angiogenesis inhibition in metastatic colorectal cancer continuum of care

Current treatment for most patients with metastatic colorectal cancer consists of sequential lines of different systemic therapies, including chemotherapy combinations (5-fluorouracil plus irinotecan or oxaliplatin) with the addition of molecular-targeted drugs, such as anti-angiogenic drugs (independently of the molecular characterisation of the tumour) or anti-epidermal growth factor receptor drugs (for patients whose tumours are wild type for KRAS and NRAS genes). More recently, for the subgroup of patients with high microsatellite instable or mismatch repair deficient tumours (approximately 5% of patients), immune checkpoint inhibitors (pembrolizumab or nivolumab plus ipilimumab) have been shown to be highly effective as first-line or second-line therapies. 1 Ciardiello F Ciardiello D Martini G Napolitano S Tabernero J Cervantes A Clinical management of metastatic colorectal cancer in the era of precision medicine. CA Cancer J Clin. 2022; 72: 372-401 Crossref PubMed Scopus (49) Google Scholar , 2 Cervantes A Adam R Roselló S et al. Metastatic colorectal cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up. Ann Oncol. 2023; 34: 10-32 Summary Full Text Full Text PDF PubMed Scopus (70) Google Scholar Furthermore, in patients whose tumours show HER2 gene amplification, BRAFV600E mutation, or KRASG12C mutation, current treatment options also incorporate the corresponding appropriate molecular-targeted drugs. 1 Ciardiello F Ciardiello D Martini G Napolitano S Tabernero J Cervantes A Clinical management of metastatic colorectal cancer in the era of precision medicine. CA Cancer J Clin. 2022; 72: 372-401 Crossref PubMed Scopus (49) Google Scholar , 2 Cervantes A Adam R Roselló S et al. Metastatic colorectal cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up. Ann Oncol. 2023; 34: 10-32 Summary Full Text Full Text PDF PubMed Scopus (70) Google Scholar Fruquintinib versus placebo in patients with refractory metastatic colorectal cancer (FRESCO-2): an international, multicentre, randomised, double-blind, phase 3 studyFruquintinib treatment resulted in a significant and clinically meaningful benefit in overall survival compared with placebo in patients with refractory metastatic colorectal cancer. These data support the use of fruquintinib as a global treatment option for patients with refractory metastatic colorectal cancer. Ongoing analysis of the quality of life data will further establish the clinical benefit of fruquintinib in this patient population. Full-Text PDF

HER2 Status Assessment in Endometrial Serous Carcinoma: Comparative Analysis of Two Proposed Testing and Interpretation Algorithms.

HER2 status is now routinely assessed in endometrial serous carcinoma (ESC) due to the reported predictive value of HER2 protein overexpression and/or gene amplification. Herein the authors compare 2 proposed testing and interpretation guidelines for HER2 in ESC. Forty-three consecutive cases of ESC that had been dually tested by both HER2 immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were interpreted using 2 sets of guidelines. Guideline set 1 (GS1) is the 2018 American Society of Clinical Oncology/College of American Pathologists guidelines for breast cancer. Guideline set 2 (GS2) is a recent proposal that is a slight modification of the enrollment criteria for the clinical trial (NCT01367002) that demonstrated a survival benefit for anti-HER2 therapy in ESC. By IHC, GS1 and GS2, respectively classified 39.5% (17/43) and 28% (12/43) of ESC as HER2-negative, 37.2% (16/43) and 53.4% (23/43) as HER2 equivocal, and 23.2% (10/43) and 18.6% (8/43) as HER2-positive (P > 0.05 for all). IHC and FISH were highly concordant at the extremes using either set of guidelines, as no cases were found to be IHC3+/FISH-negative or IHC 0-1+/FISH-positive. GS1 and GS2 were comparable regarding the proportion of IHC equivocal cases that were HER2 amplified by FISH (19% vs 23% respectively; [P = 0.71]). GS1 and GS2 displayed 98% (42/43) concordance regarding the final (IHC and/or FISH-based) classification of tumors as being HER2-positive or negative, and the same 13 cases were ultimately classified as HER2 amplified using either GS1 or GS2. One "discordant" case was classified as HER2-positive using GS2 but HER2-negative using GS1 (HER2 IHC score 2+ using both guidelines, HER2:CEP17 signal ratio of 3, HER2 signal number of 3.4). Six (14%) of the 43 cases (FISH Groups: 2, 3, and 4) would require IHC results to interpret the FISH findings using GS1. Because GS1 requires that the HER2 IHC staining be observed within a homogeneous and contiguous invasive cell population, and this is not a requirement in GS2, GS2 may be better suited for ESC given its frequently heterogeneous staining pattern. Additional studies may be required on the optimal interpretation of problematic dual-probe FISH scenarios in GS2 and the necessity for IHC correlation in such scenarios. Using either set of guidelines, our findings support a reflex testing strategy of restricting FISH testing to cases that are IHC equivocal.

Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer.

To update the American Society of Clinical Oncology-College of American Pathologists (ASCO-CAP) recommendations for human epidermal growth factor receptor 2 (HER2) testing in breast cancer. An Update Panel is aware that a new generation of antibody-drug conjugates targeting the HER2 protein is active against breast cancers that lack protein overexpression or gene amplification. The Update Panel conducted a systematic literature review to identify signals for updating recommendations. The search identified 173 abstracts. Of 5 potential publications reviewed, none constituted a signal for revising existing recommendations. The 2018 ASCO-CAP recommendations for HER2 testing are affirmed. HER2 testing guidelines have focused on identifying HER2 protein overexpression or gene amplification in breast cancer to identify patients for therapies that disrupt HER2 signaling. This update acknowledges a new indication for trastuzumab deruxtecan when HER2 is not overexpressed or amplified but is immunohistochemistry (IHC) 1+ or 2+ without amplification by in situ hybridization. Clinical trial data on tumors that tested IHC 0 are limited (excluded from DESTINY-Breast04), and evidence is lacking that these cancers behave differently or do not respond similarly to newer HER2 antibody-drug conjugates. Although current data do not support a new IHC 0 versus 1+ prognostic or predictive threshold for response to trastuzumab deruxtecan, this threshold is now relevant because of the trial entry criteria that supported its new regulatory approval. Therefore, although it is premature to create new result categories of HER2 expression (eg, HER2-Low, HER2-Ultra-Low), best practices to distinguish IHC 0 from 1+ are now clinically relevant. This update affirms prior HER2 reporting recommendations and offers a new HER2 testing reporting comment to highlight the current relevance of IHC 0 versus 1+ results and best practice recommendations to distinguish these often subtle differences. Additional information is available at www.asco.org/breast-cancer-guidelines.

New Biomarkers and Treatment Advances in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a specific subtype of breast cancer lacking hormone receptor expression and HER2 gene amplification. TNBC represents a heterogeneous subtype of breast cancer, characterized by poor prognosis, high invasiveness, high metastatic potential, and a tendency to relapse. In this review, the specific molecular subtypes and pathological aspects of triple-negative breast cancer are illustrated, with particular attention to the biomarker characteristics of TNBC, namely: regulators of cell proliferation and migration and angiogenesis, apoptosis-regulating proteins, regulators of DNA damage response, immune checkpoints, and epigenetic modifications. This paper also focuses on omics approaches to exploring TNBC, such as genomics to identify cancer-specific mutations, epigenomics to identify altered epigenetic landscapes in cancer cells, and transcriptomics to explore differential mRNA and protein expression. Moreover, updated neoadjuvant treatments for TNBC are also mentioned, underlining the role of immunotherapy and novel and targeted agents in the treatment of TNBC.

Assessment of HER2 status in extramammary Paget disease and its implication for disitamab vedotin, a novel humanized anti-HER2 antibody-drug conjugate (ADC) therapy.

e21544 Background: Evaluation of HER2 status in extramammary Paget disease (EMPD) has been reported in a few studies with a small number of samples, and the HER2 overexpression rate ranges from 15% to 60%. The prognosis of advanced EMPD is poor and the treatment options is limited. Disitamab Vedotin (DV) is a novel humanized anti-HER2 antibody-drug conjugate (ADC), has been approved for metastatic urothelial carcinoma and gastric cancer in China. To determine the HER2 status and the efficacy of DV in advanced EMPD patients (pts) harboring HER2 expression, we conducted this multicenter retrospective study. Methods: Paraffin-embedded blocks, clinic-pathological data, and survival data of EMPD pts were retrospectively collected from 3 centers in China. HER2 IHC scoring and gene amplification evaluation were carried out according to the (ASCO/CAP) 2018 guidelines. The results of FISH and IHC were analyzed by two pathologists independently in a double-blinded manner. Data analysis was performed using SPSS v.26, Prism 8 and R version 3.6.5. Results: Finally, 129 cases with detailed data were enrolled between 2006 and 2022. Among them, HER2 IHC was performed in 102 cases, and FISH in 46 cases. HER2 expression was detected in 93.1% samples, with scores of 1+, 2+, and 3+ in 47.1% (48/102), 37.3% (38/102), and 8.7% (9/102) respectively. HER2 gene amplification was detected in eight cases (8/46, 17.4%), including all the cases with IHC 3+ (5/5, 100%), two with IHC 2+ (2/18, 11.1%), and one with IHC 1+ (1/22, 4.5%). For the subgroup of HER2 2+/3+, a higher frequency of lymph node metastasis (66.7% vs 33.3%, P = 0.034) and reduced survival time were detected than in HER2 1+/0. Two elderly male pts with advanced EMPD (one HER1+ /FISH-, one HER 2+/FISH-), who failed with chemo of paclitaxel, received 4 doses of DV infusion (2mg/kg every 2 weeks), and achieved partial responses both with tolerable toxicity. Conclusions: According to the study, the expression rate of HER-2 was very high in EMPD, indicating that it may be used as a routine treatment target. DV showed efficacy in these patients and need further validation.

Correlation of HER2 low status in I-SPY2 with molecular subtype, response, and survival.

514 Background: HER2low, defined as immunohistochemical (IHC) 1+ or 2+ without HER2 gene amplification, predicted improved progression free and overall survival with trastuzumab deruxtecan (TDXd) compared to chemotherapy in patients (pts) with metastatic breast cancer in Destiny Breast04. Controversy exists regarding the correlation of HER2low with molecular subtypes and outcome. We evaluated these associations in the neoadjuvant ISPY2 trial. Methods: We investigated HER2 IHC class in pts with clinically HER2-negative breast cancer (BC) enrolled in the first 10 arms of ISPY2. To explore the biology of HER2low, we used Fisher’s exact test to assess association of IHC class (0 vs 1+ or 2+) with Response Predictive Subtypes-5 (RPS-5; based on immune, DNA repair damage (DRD), HER2, and luminal markers; PMID: 35623341), SET index [endocrine responsiveness], and Mammaprint high1 (MP1) vs high2 (MP2). Association with pathologic complete response (pCR) was assessed using Fisher’s exact test, and association with distant recurrence free survival (DRFS) was assessed using Cox Proportional Hazards modeling. Results: Of 742 HER2negative pts enrolled in the first 10 arms of ISPY2, local HER2 IHC is available for 585; 299 hormone receptor + (HR+) and 286 triple negative (TN). 63% of pts are HER2low, with HER2low status more frequent in HR+ (71%) compared to TN BC (55%; OR = 1.97; p = 0.00011). There was no clear relationship between HER2low IHC and RPS-5 subtypes or endocrine sensitivity measured by the SET index. There was no significant association of HER2low with pCR overall or within treatment arms (p > 0.05); this was true for TN and HR+ subsets. 562 pts with HER2negative disease have distant recurrence free survival (DRFS) data with a median follow-up of 4.23 yrs. Pts with pCR had excellent outcome (5yr DRFS > 94%), with no impact from HER2low vs 0 status. For pts with nonpCR, after adjusting for HR+ status, the DRFS hazard ratio for HER2low vs 0 status is not significant [0.68(0.46-1.02)]. Within HR+, HER2low is found in > 70% for both SET low and high. HR+/MP1 pts (with generally low pCR rates) are significantly more likely to be HER2low (75%; (172/219)) compared to HR+/MP2 (61%; (49/80)) (OR: 1.79; Fisher p = 0.044). Importantly, 70% of HER2-Immune-/DRD- (78% HR+ and 56% TN), a subtype with low response to all ISPY2-tested agents, are HER2Low. Conclusions: In ISPY2 which enrolls patients with MP high risk BC, HER2low by IHC was frequent and higher in HR+ than TN disease. There was no clear association with molecular markers, pCR or DRFS. The frequency of HER2low in the immune-/DRD- subtype raises the potential for exploring T-DXd in this high risk, low-response setting. Clinical trial information: NCT01042379 .

Pathological Types,Expression of Mismatch Repair Protein,Human Epidermal Growth Factor Receptor 2,and Pan-TRK,and Eostein-Barr Virus Infection in Patients With Colorectal Cancer Resected in Tibet

Objective To study the pathological types,expression of mismatch repair protein,human epidermal growth factor receptor 2(HER2),and Pan-TRK,and Epstein-Barr virus(EBV)infection in patients with colorectal cancer resected in Tibet. Methods A total of 79 patients with colorectal cancer resected in Tibet Autonomous Region People's Hospital from December 2013 to July 2021 were enrolled in this study.The clinical and pathological data of the patients were collected.The expression of mismatch repair protein,HER2,and Pan-TRK was detected by immunohistochemical(IHC)staining,and detection of HER2 gene by fluorescence in situ hybridization(FISH)in the patients with HER2 IHC results of 2+ or above.EBV was detected by in situ hybridization with EBV-encoded small RNA. Results A total of 79 colorectal cancer patients were included in this study,with the male-to-female ratio of 1.26:1 and the mean age of(57.06±12.74)years(24-83 years).Among them,4 patients received preoperative neoadjuvant therapy.Colonic cancer and rectal cancer occurred in 57(57/79,72.15%,including 31 and 26 in the right colon and left colon,respectively)and 22(22/79,27.85%)patients,respectively.The maximum diameter of tumor varied within the range of 1-20 cm,with the mean of(6.61±3.33)cm.Among the 79 colorectal cancer patients,75(75/79,94.94%)patients showed adenocarcinoma.Lymph node metastasis occurred in 12(12/21,57.14%)out of the 21 patients with severe tumor budding,13(13/23,56.52%)out of the 23 patients with moderate tumor budding,and 2(2/31,6.45%)out of the 31 patients with mild tumor budding,respectively.The lymph node metastasis rate showed differences between the patients with severe/moderate tumor budding and the patients with mild tumor budding(all P<0.001).The IHC staining showed that mismatch repair protein was negative in 10(10/65,15.38%)patients,including 5 patients with both MSH2 and MSH6 negative,4 patients with both MLH1 and PMS2 negative,and 1 patient with MSH6 negative.Pan-TRK was negative in 65 patients.The IHC results of HER2 showed 0 or 1+ in 60 patients and 2+ in 5 patients.FISH showed no positive signal in the 5 patients with HER2 IHC results of 2+.The detection with EBV-encoded small RNA showed positive result in 1(1/65,1.54%)patient. Conclusions Non-specific adenocarcinoma of the right colon is the most common in the patients with colorectal cancer resected in Tibet,and 15% of the patients showed mismatch repair protein defects.EBV-associated colorectal carcer is rare,Pan-TRK expression and HER2 gene amplification are seldom.The colorectal cancer patients with moderate and severe tumor budding are more likely to have lymph node metastasis.

Circulating tumor DNA (ctDNA) analyses in patients with HER2-positive biliary tract cancer (BTC) treated with trastuzumab deruxtecan (T-DXd): Exploratory results from the HERB trial.

4097 Background: In the phase 2 HERB trial (NCCH1805; JMA-IIA00423), T-DXd exhibited promising activity among patients with HER2-positive BTC (ASCO 2022 ab 4006). HER2 positivity was defined as tumor tissue immunohistochemistry (IHC) 3+ or IHC 2+ with in situ hybridization (ISH) positivity. HER2 gene amplification (HER2-amp) can also be detected in ctDNA, which may be an alternative when tumor tissue is not available. ctDNA may also detect tumor molecular changes during treatment and at disease progression. Methods: In this ancillary study, we collected plasma samples for ctDNA analysis (Guardant360) at baseline (BL), day 1 of cycle 2 (C2D1; ie, day 22 of treatment), and end of treatment (EOT). The relationships between clinical outcomes and ctDNA genomic profiles were evaluated. Results: Among the 30 patients in the full analysis set of HERB (22 with HER2-positive and 8 with HER2-low BTC), plasma samples for ctDNA were obtained from 30, 29, and 24 at BL, C2D1, and EOT, respectively. HER2-amp was found in ctDNA of 8 BL samples, all of which were from tissue HER2-positive patients. This included 50% (5 of 10) of the IHC 3+ tumors and 25% (3 of 12) of the IHC 2+/ISH + tumors. Comparing clinical outcomes for patients with HER2-amp in ctDNA (n=8) to those with HER2-positive in tissue (n=22), the confirmed objective response rate (cORR) was 50.0% (95% CI, 15.7–84.3), including all 2 CR cases, vs 36.4% (95% CI, 17.2–59.3); median duration of response was 7.9 (95% CI, 2.8–11.5) vs 7.4 months (95% CI, 2.8–NA), median progression-free survival (PFS) was 6.1 (95% CI, 2.8–20.3) vs 5.1 months (95% CI, 3.0–7.3), and median overall survival was 10.8 (95% CI, 4.7–NA) vs 7.1 months (95% CI, 4.7–14.6). Plasma copy number (median 5.1, range 2.3–9.9) was not associated with response or survival, even after adjusting for maximum variant allele frequency (MAF). Common BL genomic mutations found in ctDNA were in TP53 (n=19, 63%), PIK3CA (n=8, 27%), and TERT (n=7, 23%). No mutation was associated with treatment efficacy. Median MAF decreased from 7.3% at BL to 1.6% at C2D1. Decreased MAF was associated with better response (CR, PR, and SD) and longer PFS. Among 24 EOT samples, including 7 from patients with BL HER2-amp in ctDNA, 10 (42%) acquired potential resistance alterations, most related to receptor tyrosine kinase, MAPK, and PI3K pathways. HER2-amp was lost at EOT in 4 of the 7 patients with HER2-amp detected in BL ctDNA. Conclusions: Using a ctDNA assay, HER2-amp was detected in 36% of patients with tissue HER2-positive BTC. Those with HER2-amp in ctDNA than HER2-positive in tissue had potentially higher cORR and longer survival with TDXd. Clinical trial information: JMA-IIA00423 .

Efficacy and safety of KN026 in combination with KN046 in patients with locally advanced unresectable or metastatic HER2-positive other solid tumors.

3621 Background: Besides breast cancer (BC) and gastric cancer, HER2 is also widely expressed in other solid tumors, such as colorectal cancer (CRC), NSCLC, gallbladder cancer (GBC), renal pelvis cancer (RPC), pancreatic ductal adenocarcinoma (PDAC), etc. The reports of immunotherapy combined with HER2-targeted therapy are limited. KN026 is a novel bispecific antibody that simultaneously binds to two distinct HER2 epitopes. KN046 is a novel bispecific antibody that blocks both PD-L1 interaction with PD-1 and CTLA-4 interaction with CD80/CD86. Methods: KN026-203 study (NCT04521179) is an open-label, phase II, multi-center study to evaluate the efficacy and safety of KN026 (30mg/kg, Q3W, C1D1 and C1D8 loading) combined with KN046 (5mg/kg, Q3W) in patients (pts) with HER2-positive (defined as HER2 IHC 3+ or HER2 gene amplification) solid tumors. The study consisted of 3 cohorts, including HER2 positive gastric or gastroesophageal cancer (GC/GEJ), BC and other solid tumors. Pts received treatment until disease progression or unacceptable toxicity. Tumor assessments were scheduled every 6 weeks. The primary endpoints were ORR and DOR. The efficacy and safety of KN026 combined with KN046 were reported. Results: As of 10 November 2022, 26 pts with HER2 positive tumor other than BC and GC/GEJ were enrolled, including 15 CRC, 5 NSCLC, 4 GBC, 1 RPC and 1 PADC pts. All those pts had previous systemic treatment. The median age was 56 (range 37 ~ 67) years. 15 (57.7%) pts had liver metastasis. 92.3% of pts and all CRC pts had received ≥2 lines prior treatment. 5 (19.2%) and 6 (23.1%) pts had received prior anti-HER2 and anti-PD-(L)1 therapy, respectively. All 26 pts were assessed according to RECIST v1.1. The confirmed ORR was 53.8% (95% CI: 33.4, 73.4) with mDOR 6.8 months (95% CI: 2.9, 15.3). The mPFS was 5.6 months (95% CI: 2.9, 16.5) and 12-month OS rate was 80.4% (95% CI: 59.1, 91.4) with median follow-up time 16.6 months. For 15 CRC pts, the ORR was 53.3% (95% CI: 26.6, 78.7) with mDOR 11.7 months (95% CI: 3.2, NE). The mPFS was 12.2 months (95% CI: 2.7, NE) .12-month OS rate was 80.0% (95% CI: 50.0, 93.1) with median follow-up time 16.0 months. Common TRAEs were infusion related reaction (38.5%), AST increased (34.6%), ALT increased (26.9%), conjugated bilirubin increased (26.9%), rash (26.9%), anemia (26.9%) and blood bilirubin increased (26.9%). Most of them were Grade 1 or 2. The most common ≥ Gr3 TRAEs were conjugated bilirubin increased (7.7%) and AST increased (7.7%). There was no treatment related death. Conclusions: KN026 combined with KN046 treatment had demonstrated favorable efficacy and safety profile in HER2 positive other solid tumors (non-GC/GEJ and non-BC). Especially very promising efficacy were observed in ≥3 lines HER2 positive CRC. Based on these results, a pivotal study was planned to verify the efficacy and safety of KN026 and KN046 combo. Clinical trial information: NCT04521179 .

Tissue-agnostic efficacy of trastuzumab deruxtecan (T-DXd) in advanced solid tumors with HER2 amplification identified by plasma cell-free DNA (cfDNA) testing: Results from a phase 2 basket trial (HERALD/EPOC1806).

3014 Background: HER2 ( ERBB2) gene amplification (amp) is a potential therapeutic target beyond breast and gastric cancers. HER2 amp can be detected in plasma cfDNA which may be an alternative to tissue biopsy. HERALD/EPOC1806 was a multicenter, investigator-initiated phase 2 trial of T-DXd for patients with HER2-amplified advanced solid tumors identified by cfDNA testing. Methods: We enrolled adults with advanced solid tumors harboring HER2 amp detected by next-generation sequencing of cfDNA (Guardant360) in the GOZILA study (UMIN000029315). We excluded breast or gastric cancer patients with HER2 overexpression (IHC 3+ or IHC 2+/ISH+). Patients received T-DXd 5.4 mg/kg every 3 weeks until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed objective response rate (ORR). Results: From December 2019 to January 2022, 4,734 patients were screened by cfDNA in the GOZILA study. Among 252 with HER2 amp, 62 with 16 cancer types were enrolled in HERALD. Median baseline plasma HER2 copy number (CN) was 8.55 (range, 2.4–73.9). All patients but 3 (all with salivary gland cancer) received prior anti-cancer therapy (median, 3 lines; range, 0–8). At a median follow-up of 8.9 months (data cut-off: July 17, 2022), the confirmed ORR was 56.5% (95% CI, 43.3–69.0%), statistically higher than the threshold value of 5%. Responses were observed for 13 cancer types, including KRAS-mutant colorectal (1/3), PIK3CA-mutant endometrial (5/6), and tissue HER2-negative gastric cancers (1/2). Plasma HER2 CN above vs. below the baseline median value did not impact response (ORR: 58.1% vs. 54.8%); however, the clearance vs. persistence of HER2 amp in cfDNA on Cycle 2 Day 1 corresponded to higher response (ORR: 88.0% vs. 22.7%). ORR by independent review was 58.1% (95% CI, 44.8–70.5%), and the disease control rate was 90.3% (95% CI, 80.1–96.4%). Median progression-free survival was 7.0 (95% CI, 4.9–9.7) months, and the median duration of response was 8.8 months (95% CI, 5.8–11.2). Most adverse events were mild to moderate. Interstitial lung diseases occurred in 16 patients (25.8%, G1/G2/G3; 14/1/1). Conclusions: T-DXd achieved a high ORR, durable response with a manageable safety profile in patients with advanced solid tumors and HER2 amp detected in cfDNA. Clinical trial information: JapicCTI-194707 .[Table: see text]

Association of HER2/CEP17 ratio with pCR after HER2-directed neoadjuvant treatments in the phase III NeoALTTO trial.

600 Background: HER2-directed therapies are approved for the treatment of patients with HER2-positive invasive breast cancer as defined by HER2 protein overexpression, or HER2 gene amplification based on HER2/chromosome enumeration probe (CEP17) ratio ≥ 2.2. Above this accepted HER2 status determination, however, it is still unknown whether the efficacy of HER2-directed therapy in early breast cancer increases with increasing HER2/CEP17 ratios. Therefore, the purpose of the presented work is to evaluate whether quantitative assessment of the HER2/CEP17 ratio predicts pathological complete response (pCR) and event-free survival (EFS) of patients treated with neo-adjuvant HER2-based regimen in the prospective phase III NeoALTTO trial. Methods: 455 women with HER2-positive early breast cancer, who had received neo-adjuvant trastuzumab and/or lapatinib for 6 weeks and then together with 12 cycles of weekly paclitaxel were included in this analysis. The HER2/CEP17 ratio in the primary tumor samples was correlated with pCR and survival outcome. Results: The Median HER2/CEP17 ratio in NeoALTTO was 5.1 (range: 1.1 – 100.0), and ratios were not associated with age, hormone receptor status, or any of the other clinicopathological variables analyzed. The log HER2/CEP17 ratio significantly predicted for pCR in both uni-variate (OR: 1.83; 95% CI: 1.11 - 3.01, p = 0.0176) and multivariate analysis (OR: 1.79; 95% CI: 1.07 - 2.99, p = 0.0257). Higher HER2/CEP17 ratios were, however, not associated with improved EFS (adjusted HR = 0.79; p = 0.3537). A pCR prediction model which included HER2/CEP17 ratio, treatment arm, and hormone receptor status improved the predictive strength of treatment arm alone from a ROC AUC value of 0.60 to 0.69. Conclusions: In patients treated with HER2-based neoadjuvant therapy, quantitative analysis of the readily available pre-treatment HER2/CEP17 ratio by FISH is predictive of pCR but not EFS.

A Comprehensive Review on the Role of Human Epidermal Growth Factor Receptor 2 (HER2) as a Biomarker in Extra-Mammary and Extra-Gastric Cancers

The human epidermal growth factor receptors (HERs) are expressed abundantly in the human body. The tumorigenic potential of HER2/neu is linked to its overexpression, amplification or somatic mutation. The HER2 gene amplification leading to protein overexpression has been reported in 25–30% of breast cancers and 10–30% of gastric/gastroesophageal cancers. While HER2 is a well-documented predictive, prognostic, and therapeutic marker in breast and gastric/gastroesophageal cancers, its relevance has also been demonstrated in multiple other malignancies. In this article, we will conduct an extensive review of current data pertaining to HER2 amplification, overexpression, or mutation in cancers other than breast and gastric cancers.

A Multiparameter Molecular Classifier to Predict Response to Neoadjuvant Lapatinib plus Trastuzumab without Chemotherapy in HER2+ Breast Cancer.

Clinical trials reported 25% to 30% pathologic complete response (pCR) rates in HER2+ patients with breast cancer treated with anti-HER2 therapies without chemotherapy. We hypothesize that a multiparameter classifier can identify patients with HER2-"addicted" tumors who may benefit from a chemotherapy-sparing strategy. Baseline HER2+ breast cancer specimens from the TBCRC023 and PAMELA trials, which included neoadjuvant treatment with lapatinib and trastuzumab, were used. In the case of estrogen receptor-positive (ER+) tumors, endocrine therapy was also administered. HER2 protein and gene amplification (ratio), HER2-enriched (HER2-E), and PIK3CA mutation status were assessed by dual gene protein assay (GPA), research-based PAM50, and targeted DNA-sequencing. GPA cutoffs and classifier of response were constructed in TBCRC023 using a decision tree algorithm, then validated in PAMELA. In TBCRC023, 72 breast cancer specimens had GPA, PAM50, and sequencing data, of which 15 had pCR. Recursive partitioning identified cutoffs of HER2 ratio ≥ 4.6 and %3+ IHC staining ≥ 97.5%. With PAM50 and sequencing data, the model added HER2-E and PIK3CA wild-type (WT). For clinical implementation, the classifier was locked as HER2 ratio ≥ 4.5, %3+ IHC staining ≥ 90%, and PIK3CA-WT and HER2-E, yielding 55% and 94% positive (PPV) and negative (NPV) predictive values, respectively. Independent validation using 44 PAMELA cases with all three biomarkers yielded 47% PPV and 82% NPV. Importantly, our classifier's high NPV signifies its strength in accurately identifying patients who may not be good candidates for treatment deescalation. Our multiparameter classifier differentially identifies patients who may benefit from HER2-targeted therapy alone from those who need chemotherapy and predicts pCR to anti-HER2 therapy alone comparable with chemotherapy plus dual anti-HER2 therapy in unselected patients.

Investigation of HER2 gene amplification and protein expression in canine primary pulmonary carcinoma

Investigation of HER2 gene amplification and protein expression in canine primary pulmonary carcinoma