Minimum biopsy set for HER2 evaluation in gastric and gastro-esophageal junction cancer

Evolving Landscape of HER2-Targeted Therapies for Gastric Cancer Patients

OPINION STATEMENT

Gastric cancer (GC) is a deadly disease worldwide, and trastuzumab in combination with chemotherapy has been the standard first-line treatment for HER2-positive GC following the TOGA trial. Besides adjuvant therapy, HER2-directed therapy is widely used as neoadjuvant or translational therapy, and survival benefit even surgical opportunities is seen in these patients. However, resistance is not rare in recent years, and the second-line treatment for trastuzumab beyond progression has received widespread attention in GC. Moreover, current evidence cannot recommend trastuzumab for patients with IHC1+ HER2 low expression GC yet. Researchers are currently investigating whether GC patients with low HER2 expression could also benefit from HER2-directed therapies. In addition to using HER2 as a target for targeted therapy, HER2-mediated targeted delivery of cytotoxic drugs and targeted immunity have made important contributions to overcoming trastuzumab resistance in recent trials. HER2/neu-derived peptide epitopes vaccination and HER2-specific chimeric antigen receptor (CAR) therapy focus on reestablishing anti-tumor immunity in different ways and show significant anti-tumor activity. Other antibodies that target different regions of the HER2 receptor or block key downstream pathways such as AKT or PI3K also offer potential anti-tumor activity against HER2. HER2 use in GC will not be hampered by resistance or low expression and will play a bigger role. We review the current efforts to enable GC patients with trastuzumab-resistant and HER2 low-expressing accessible to HER2 targeted therapy and present our consideration for future HER2 in GC.

Spatial and Temporal Tumor Heterogeneity in Gastric Cancer: Discordance of Predictive Biomarkers

Gastric cancer (GC) is a highly heterogeneous disease that varies in both histological presentation and genetic characteristics. Recent advances in the treatment of metastatic and unresectable GC have made several biomarker tests essential for patient management. Predictive biomarkers such as human epidermal growth factor receptor 2 (HER2), programmed death-ligand 1 (PD-L1), mismatch-repair (MMR) proteins, claudin 18.2, and fibroblast growth factor receptor 2b (FGFR2b) are commonly evaluated using immunohistochemistry. However, the expression levels of these biomarkers may vary across different tumor areas, and the accuracy of biomarker diagnosis can be affected by sample quantity, sample location, and collection method. Therefore, tumor heterogeneity presents substantial challenges for accurate biomarker-based diagnosis and prediction of therapeutic responses. Tumor heterogeneity can be categorized into spatial heterogeneity, which refers to variations within the primary tumor (intra-tumoral) or between primary and metastatic sites, and temporal heterogeneity, which encompasses changes over time. This review addresses the tumor heterogeneity in predictive biomarker expression in GC, focusing on HER2, PD-L1, MMR, the Epstein-Barr virus, claudin 18.2, and FGFR2b.

Resistance to Anti-HER2 Therapies in Gastrointestinal Malignancies

Human epidermal growth factor 2 (HER2) is a tyrosine kinase receptor that interacts with multiple signaling pathways related to cellular growth and proliferation. Overexpression or amplification of HER2 is linked to various malignancies, and there have been decades of research dedicated to targeting HER2. Despite the landmark ToGA trial, progress in HER2-positive gastrointestinal malignancies has been hampered by drug resistance. This review examines current HER2 expression patterns and therapies for gastroesophageal, colorectal, biliary tract, and small bowel cancers, while dissecting potential resistance mechanisms that limit treatment effectiveness.

Claudin-18.2 testing and its impact in the therapeutic management of patients with gastric and gastroesophageal adenocarcinomas: A literature review with expert opinion

Claudin-18.2 (CLDN18.2) is a member of the tight junction protein family and is a highly selective biomarker with frequent abnormal expression during the occurrence and development of various primary malignant tumors, including gastric cancer (GC) and esophago-gastric junction adenocarcinomas (EGJA). For these reasons, CLDN18.2 has been investigated as a therapeutic target for GC/EGJA malignancies. Recently, zolbetuximab has been proposed as a new standard of care for patients with CLDN18.2-positive, HER2-negative, locally advanced and metastatic GC/EGJA. The use of CLDN18 IHC assays to select patients who might benefit from anti-CLDN18.2 therapy is currently entering clinical practice. In this setting, pathologists play a central role in therapeutic decision-making. Accurate biomarker assessment is essential to ensure the best therapeutic option for patients. In the present review, we provide a comprehensive overview of available evidence on CLDN18.2 testing and its impact on the therapeutic management of patients with GC/EGJA, as well as some practical suggestions for CLDN18.2 staining interpretation and potential pitfalls in the real-world setting.

The risk of weekend biopsy: Impact of specimen source and fixation status on HER2 assessment in the treatment of advanced gastric cancer (The HER_WEEKEND study)

Accurate evaluation of human epidermal growth factor receptor type 2 (HER2) expression is crucial for determining chemotherapy regimens in gastric cancer. However, formalin fixation status has been identified as an important factor affecting HER2 assessment reliability. This retrospective cohort study aimed to investigate the correlation between sample collection day (weekday vs. weekend) and source (biopsy vs. surgical specimens) in assessing HER2 expression in patients with unresectable advanced/recurrent gastric cancer. Data were collected from gastric cancer patients who received chemotherapy at a single public hospital in Japan from 2008 to 2021. The analysis included 177 patients (109 men, 68 women) with a median age of 68.0 (21-88) years, and the primary outcome was the HER2 positivity rate. The overall HER2 positivity rate was 18.1%, with higher rates on weekdays (20.0%) compared to weekends (12.8%). Biopsies had higher positivity rates on weekdays (23.9%) but lower rates on weekends (11.1%) than surgical specimens. Significant differences were observed in formalin fixation times between weekdays and weekends for both biopsies and surgical samples. The study findings suggest that longer formalin fixation times on weekends may lead to underestimating HER2 expression, particularly in biopsies. Therefore, it is crucial to be cautious of excessive formalin fixation when collecting samples, especially during weekend biopsies.

Epidemiology, Risk Factors for Gastric Cancer and Surveillance of Premalignant Gastric Lesions: A Prospective Cohort Study of Central Saudi Arabia

(1) Background: Saudi Arabia (SA) is a country with a low incidence of gastric cancer (GC). In this study, we sought to assess the epidemiology of GC, its clinicopathological profiles, and its association with risk factors as well as to identify premalignant gastric lesions (PGL) and examine neoplastic progression. (2) Methods: This five-year prospective study screened for GC and PGL in asymptomatic Saudi patients, aged 45-75 years (n = 35,640) and living in Al Kharj, Riyadh province in central SA. Those who were positive in a high-sensitivity guaiac fecal occult blood test (HSgFOBT+) and had negative results in colonoscopy offered to undergo upper GI endoscopy (n = 1242). Factors associated with GC were examined. (3) Results: The five-year participation rate was 87% (1080/1242). The incidence rate of GC was 26.9 new cases per 100,000 population per year (9.6 new cases per year/total population at risk-35,640), and it was 8.9 cases per 1000 persons per year among the 1080 subjects with HSgFOBT+ and negative colonoscopy results. The five-year mortality rate was 67% among patients with GC (n = 48), 3.0% among participants in the gastric screening program (n = 1080) and 0.09% among the original population participating in the colorectal screening program (n = 35,640). Intestinal-type adenocarcinoma was the most frequent type (77%), with the tumor most commonly located in the antrum (41%). Overall, 334 participants had PGL, and seven of them (2.1%) showed neoplastic progression to GC during the follow-up. Factors associated with GC were age, Helicobacter pylori (HP) infection, obesity (body mass index BMI > 30), smoking, a diet of salty preserved foods, low income and a family history of GC. (4) Conclusions: The incidence of GC is low in central SA, but screening for PGL and GC among patients with HSgFOBT+ and negative colonoscopy may prevent or result in the early treatment of GC. HP eradication, normal body weight, not smoking and adhering to a healthy diet can reduce the risk of GC. The resulting data provide important input for the improvement of national guidelines.

Role of Endoscopic Biopsies and Morphologic Features in Predicting Microsatellite Instability Status in Gastric Cancer: A Multicenter Comparative Study of Endoscopic Biopsies and Surgical Specimens

Evaluation of mismatch repair (MMR) protein and microsatellite instability (MSI) status plays a pivotal role in the management of gastric cancer (GC) patients. In this study, we aimed to evaluate the accuracy of gastric endoscopic biopsies (EBs) in predicting MMR/MSI status and to uncover histopathologic features associated with MSI. A multicentric series of 140 GCs was collected retrospectively, in which EB and matched surgical specimens (SSs) were available. Laurén and WHO classifications were applied and detailed morphologic characterization was performed. EB/SS were analyzed by immunohistochemistry (IHC) for MMR status and by multiplex polymerase chain reaction (mPCR) for MSI status. IHC allowed accurate evaluation of MMR status in EB (sensitivity: 97.3%; specificity: 98.0%) and high concordance rates between EB and SS (Cohen κ=94.5%). By contrast, mPCR (Idylla MSI Test) showed lower sensitivity in evaluating MSI status (91.3% vs. 97.3%), while maintaining maximal specificity (100.0%). These results suggest a role of IHC as a screening method for MMR status in EB and the use of mPCR as a confirmatory test. Although Laurén/WHO classifications were not able to discriminate GC cases with MSI, we identified specific histopathologic features that are significantly associated with MMR/MSI status in GC, despite the morphologic heterogeneity of GC cases harboring this molecular phenotype. In SS, these features included the presence of mucinous and/or solid components ( P =0.034 and <0.001) and the presence of neutrophil-rich stroma, distant from tumor ulceration/perforation ( P <0.001). In EB, both solid areas and extracellular mucin lakes were also discriminating features for the identification of MSI-high cases ( P =0.002 and 0.045).

Evaluating mismatch repair deficiency in colorectal cancer biopsy specimens

Mismatch repair (MMR) testing on all new cases of colorectal cancer (CRC) has customarily been preferably performed on surgical specimens, as more tissue is available; however, new clinical trials for the use of immune checkpoint inhibitors in the neoadjuvant setting require MMR testing on biopsy samples. This study aims at identifying advantages, disadvantages and any potential pitfalls in MMR evaluation on biopsy tissue and how to cope with them. The study is prospective-retrospective, recruiting 141 biopsies (86 proficient (p)MMR and 55 deficient (d)MMR) and 97 paired surgical specimens (48 pMMR; 49 dMMR). In biopsy specimens, a high number of indeterminate stains was observed, in particular for MLH1 (31 cases, 56.4%). The main reasons were a punctate nuclear expression of MLH1, relatively weak MLH1 nuclear expression compared to internal controls, or both (making MLH1 loss difficult to interpret), which was solved by reducing primary incubation times for MLH1. A mean of  ≥ 5 biopsies had adequate immunostains, compared to ≤ 3 biopsies in inadequate cases. Conversely, surgical specimens rarely suffered from indeterminate reactions, while weaker staining intensity (p < 0.007) for MLH1 and PMS2 and increased patchiness grade (p < 0.0001) were seen. Central artefacts were almost exclusive to surgical specimens. MMR status classification was possible in 92/97 matched biopsy/resection specimen cases, and all of these were concordant (47 pMMR and 45 dMMR). Evaluation of MMR status on CRC biopsy samples is feasible, if pitfalls in interpretation are known, making laboratory-specific appropriate staining protocols fundamental for high-quality diagnoses.

HER2-Positive Gastric Cancer: The Role of Immunotherapy and Novel Therapeutic Strategies

Gastric cancer is an aggressive disease with increasing global incidence in recent years. Human epidermal growth receptor 2 (HER2) is overexpressed in approximately 10-20% of gastric cancers. The implementation of targeted therapy against HER2 as part of the standard of care treatment in metastatic disease has improved the prognosis of this subset of patients. However, gastric cancer still has high mortality rates and urgently requires new treatment strategies. The combination of immunotherapy with HER2-targeted therapies has shown synergistic effects in preclinical models, this being the rationale behind exploring this combination in clinical trials in locally advanced and metastatic settings. Additionally, the irruption of antibody-drug conjugates and other novel HER2-targeted agents has led to the development of numerous clinical trials showing promising results. This review presents the molecular mechanisms supporting the use of HER2-targeted drugs in combination with immunotherapy and provides an overview of the therapeutic scenario of HER2-positive disease. We focus on the role of immunotherapy but also summarize emerging therapies and combinations under clinical research that may change the standard treatment in HER-2 positive disease in the future.

State of the Art: ctDNA in Upper Gastrointestinal Malignancies

Circulating tumor DNA (ctDNA) has emerged as a promising non-invasive source to characterize genetic alterations related to the tumor. Upper gastrointestinal cancers, including gastroesophageal adenocarcinoma (GEC), biliary tract cancer (BTC) and pancreatic ductal adenocarcinoma (PADC) are poor prognostic malignancies, usually diagnosed at advanced stages when no longer amenable to surgical resection and show a poor prognosis even for resected patients. In this sense, ctDNA has emerged as a promising non-invasive tool with different applications, from early diagnosis to molecular characterization and follow-up of tumor genomic evolution. In this manuscript, novel advances in the field of ctDNA analysis in upper gastrointestinal tumors are presented and discussed. Overall, ctDNA analyses can help in early diagnosis, outperforming current diagnostic approaches. Detection of ctDNA prior to surgery or active treatment is also a prognostic marker that associates with worse survival, while ctDNA detection after surgery is indicative of minimal residual disease, anticipating in some cases the imaging-based detection of progression. In the advanced setting, ctDNA analyses characterize the genetic landscape of the tumor and identify patients for targeted-therapy approaches, and studies show variable concordance levels with tissue-based genetic testing. In this line, several studies also show that ctDNA serves to follow responses to active therapy, especially in targeted approaches, where it can detect multiple resistance mechanisms. Unfortunately, current studies are still limited and observational. Future prospective multi-center and interventional studies, carefully designed to assess the value of ctDNA to help clinical decision-making, will shed light on the real applicability of ctDNA in upper gastrointestinal tumor management. This manuscript presents a review of the evidence available in this field up to date.

Current molecular biomarkers evaluation in gastric/gastroesophageal junction adenocarcinoma: pathologist does matter

The comprehensive molecular characterization of gastric and gastroesophageal junction adenocarcinomas has led to the improvement of targeted and more effective treatments. As a result, several biomarkers have been introduced into clinical practice and the implementation of innovative diagnostic tools is under study. Such assessments are mainly based on the evaluation of limited biopsy material in clinical practice. In this setting, the pathologist represents a key player in the selection of patients facilitating precision medicine approaches.

Association of CLDN18 Protein Expression with Clinicopathological Features and Prognosis in Advanced Gastric and Gastroesophageal Junction Adenocarcinomas

The tight junction protein claudin-18 (CLDN18), is often expressed in various cancer types including gastric (GC) and gastroesophageal adenocarcinomas (GECs). In the last years, the isoform CLDN18.2 emerged as a potential drug target in metastatic GCs, leading to the development of monoclonal antibodies against this protein. CLDN18.2 is the dominant isoform of CLDN18 in normal gastric and gastric cancer tissues. In this work, we evaluated the immunohistochemical (IHC) profile of CLDN18 and its correlation with clinical and histopathological features including p53, E-cadherin, MSH2, MSH6, MLH1, PMS2, HER2, EBER and PD-L1 combined positive score, in a large real-world and mono-institutional series of advanced GCs (n = 280) and GECs (n = 70). The association of IHC results with survival outcomes was also investigated. High membranous CLDN18 expression (2+ and 3+ intensity ≥75%) was found in 117/350 (33.4%) samples analyzed. CLDN18 expression correlated with age <70 (p = 0.0035), positive EBV status (p = 0.002), high stage (III, IV) at diagnosis (p = 0.003), peritoneal involvement (p < 0.001) and lower incidence of liver metastases (p = 0.013). CLDN18 did not correlate with overall survival. The predictive value of response of CLDN18 to targeted agents is under investigation in several clinical trials and further studies will be needed to select patients who could benefit from these therapies.

The impact of recent next generation sequencing and the need for a new classification in gastric cancer

The phenotypical and molecular heterogeneity of gastric cancer has hampered the introduction in clinical practice of a unifying classification of the disease. However, as next generation sequencing (NGS) technologies enhanced the comprehension of the molecular landscape of gastric cancer, novel molecular classification systems have been proposed, allowing the dissection of molecular tumor heterogeneity and paving the way for the development of new targeted therapies. Moreover, the use of NGS analyses in the molecular profiling of formalin-fixed paraffin-embedded (FFPE) specimens will improve patient selection for the enrolment in novel clinical trials. In conclusion, the application of NGS in precision oncology will revolutionize the diagnosis and clinical management in gastric cancer patients.

Optimized PD-L1 scoring of gastric cancer

BACKGROUND

PD-1/PD-L1-Immunotherapy has been approved for gastric carcinoma. PD-L1 assessment by immunohistochemistry is the principle biomarker. Are biopsies able to map the actual PD-L1 status of the entire tumor?

METHODS

Whole tumor slides of 56 gastric carcinoma were analyzed to determine the distribution of PD-L1 positive cells in the entire tumor areas. Tissue micro arrays with four cores of the tumor surface, which represents the endoscopically accessible biopsy zone, were built from the same tumors. The PD-L1 CPS value was determined separately for each core. Preoperative diagnostic biopsies were available for 22 of the tumors. PD-L1 prevalence, sensitivity and specificity were analyzed using the whole tumor slides as reference scores. Molecular subtyping was performed and related to the PD-L1 status.

RESULTS

27.3% of cases were PD-L1 negative (CPS < 1), 43.6% showed low PD-L1 expression (CPS ≥ 1 to < 5), 12.7% moderate (CPS ≥ 5 to < 10) and 16.4% strong expression (CPS ≥ 10). The biopsies showed best test characteristics if four surface biopsies were analyzed combined, i.e., the CPS was calculated across all four biopsies. The prevalence showed a distribution similar to the resection specimens, sensitivity was 0.73 and specificity 1.0. Using fewer surface biopsies decreased sensitivity and specificity and caused false-negative classifications. Compared to the TMAs, the preoperative biopsies showed reduced sensitivity (0.412).

CONCLUSIONS

This is the first comprehensive study to optimize PD-L1 assessment in gastric cancer using endoscopically available tissue. The obtained PD-L1 prevalence is consistent with data of current clinical studies. Calculation of the test characteristics shows that surface biopsies can be indicative of the true PD-L1 status based on the resection specimen. However, an adequate number of biopsies is required. In this study, n = 4 biopsies yielded best results.

Intratumoral and intertumoral heterogeneity of HER2 immunohistochemical expression in gastric cancer

BACKGROUND

Given the high heterogeneity of tumor tissue in gastric cancer (GC), inaccurate detection of tumor biomarkers will inevitably hamper a precise diagnosis and selection of patients for targeted therapies. Human epidermal growth factor receptor 2 (HER2) has been widely accepted as an underlying treatment biomarker of GC. The objective of this study is to investigate the heterogeneity (both intratumoral and intertumoral) of HER2 expression in GC, and the relationship between heterogeneity and the clinicopathological features.

METHODS

A total of 618 patients with primary gastric adenocarcinoma were recruited, and two formalin-fixed paraffin-embedded (FFPE) tumor-containing blocks of each patient were selected for HER2 immunohistochemical (IHC) assay. Clinicopathological characteristics were recorded, and intratumoral and intertumoral heterogeneity of HER2 IHC expression was determined.

RESULTS

The results indicated that the dual-block assays significantly increased the HER2 overexpression (IHC 2+ and 3+) rate compared with the single paraffin block detection. Approximately 50 % of the cases showed intratumoral HER2 heterogeneity within a single tissue section, and 30.10 % of cases showed intertumoral heterogeneity between a patient's two blocks. Furthermore, intertumoral heterogeneity was associated with tumors of small size (P = 0.029) and distal location (P = 0.032) characters, while the intratumoral heterogeneity was correlated with poorly differentiated carcinomas. Laurén's diffuse type showed a notably higher intratumoral heterogeneity rate, and the mixed type exhibited higher intertumoral HER2 discordance between the dual-block cohorts (P < 0.001). Besides, HER2 heterogenous overexpression was not associated with age, gender, type of resection, lymphatic or venous invasion, perineural invasion or pTNM (P > 0.05) for both cohorts.

CONCLUSION

The research findings in this paper indicate that the intratumoral and intertumoral heterogeneity of HER2 overexpression is common in GC patients, and these variations are associated with certain clinicopathological features. We highly recommend multi-block HER2 assessment for accurate diagnosis of GC.

Neoplastic and pre-neoplastic lesions of the oesophagus and gastro-oesophageal junction

Oesophageal and gastro-oesophageal junction (GOJ) neoplasms, and their predisposing conditions, may be encountered by the practicing pathologist both as biopsy samples and as surgical specimens in daily practice. Changes in incidence of oesophageal squamous cell carcinomas (such as a decrease in western countries) and in oesophageal and GOJ adenocarcinomas (such as a sharp increase in western countries) are being reported globally. New modes of treatment have changed our histologic reports as specific aspects must be detailed such as in post endoscopic resections or with regards to post neo-adjuvant therapy tumour regression grades. The main aim of this overview is therefore to provide an up-to-date, easily available and clear diagnostic approach to neoplastic and pre-neoplastic conditions of the oesophagus and GOJ, based on the most recent available guidelines and literature.

Precancerous lesions of the stomach, gastric cancer and hereditary gastric cancer syndromes

Gastric cancer accounts for about 6% of cancers worldwide, being the fifth most frequently diagnosed malignancy and the third leading cause of cancer related death. Gastric carcinogenesis is a multistep and multifactorial process and is the result of the complex interplay between genetic susceptibility and environmental factors. The identification of predisposing conditions and of precancerous lesions is the basis for screening programs and early stage treatment. Furthermore, although most gastric cancers are sporadic, familial clustering is observed in up to 10% of patients. Among them, hereditary cases, related to known cancer susceptibility syndromes and/or genetic causes are thought to account for 1-3% of all gastric cancers. The pathology report of gastric resections specimens therefore requires a standardized approach as well as in depth knowledge of prognostic and treatment associated factors.

Current prognostic and predictive biomarkers for gastrointestinal tumors in clinical practice

The pathologist emerged in the personalized medicine era as a central actor in the definition of the most adequate diagnostic and therapeutic algorithms. In the last decade, gastrointestinal oncology has seen a significantly increased clinical request for the integration of novel prognostic and predictive biomarkers in histopathological reports. This request couples with the significant contraction of invasive sampling of the disease, thus conferring to the pathologist the role of governor for both proper pathologic characterization and customized processing of the biospecimens. This overview will focus on the most commonly adopted immunohistochemical and molecular biomarkers in the routine clinical characterization of gastrointestinal neoplasms referring to the most recent published recommendations, guidelines and expert opinions.

Pathological Tumor Regression Grade Classifications in Gastrointestinal Cancers: Role on Patients' Prognosis

Preoperative chemotherapy or combined radiotherapy and chemotherapy (CRT), followed by surgery, represents the standard approach for locally advanced esophageal, gastric, and rectal carcinomas. To adequately evaluate the effects of neoadjuvant CRT in the resection specimens, several histopathologic tumor regression grade (TRG) scoring systems have been introduced into clinical practice. The primary goal of these TRG systems relies on a correct prognostic stratification of patients in the attempt to help clinical decision-making and influence surgical strategies, postoperative adjuvant therapies, and surveillance intensity. However, most TRG systems suffer from poor reproducibility and low interobserver concordance rates. Many efforts have been made in the identification of alternative, robust, simple, and universally accepted TRG scoring systems, which would help in the comparison of different treatment strategies and in the standardization of multimodal therapies. The aim of this review is to analyze the most commonly used TRG systems in gastrointestinal cancers highlighting their pitfalls and usefulness, depending on the tumor type.

HER2 heterogeneity is a poor prognosticator for HER2-positive gastric cancer

BACKGROUND

The clinical significance of intratumoral human epidermal growth factor receptor 2 (HER2) heterogeneity is unclear for HER2-positive gastric cancer, although it has been reported to be a significant prognosticator for HER2-positive breast cancer, which has received trastuzumab-based chemotherapy.

AIM

To clarify the clinical significance of intratumoral HER2 heterogeneity for HER2-positive gastric cancer, which has received trastuzumab-based chemotherapy.

METHODS

Patients with HER2-positive unresectable or metastatic gastric cancer who received trastuzumab-based chemotherapy as a first line treatment were included. The patients were classified into two groups according to their intratumoral HER2 heterogeneity status examined by immunohistochemistry (IHC) on endoscopic biopsy specimens before treatment, and their clinical response to chemotherapy and survival were compared.

RESULTS

A total of 88 patients were included in this study, and HER2 heterogeneity was observed in 23 (26%) patients (Hetero group). The overall response rate was significantly better in patients without HER2 heterogeneity (Homo group) (Homo vs Hetero: 79.5% vs 35.7%, P = 0.002). Progression-free survival of trastuzumab-based chemotherapy was significantly better in the Homo group (median, 7.9 vs 2.5 mo, HR: 1.905, 95%CI: 1.109-3.268). Overall survival was also significantly better in the Homo group (median survival time, 25.7 vs 12.5 mo, HR: 2.430, 95%CI: 1.389-4.273). Multivariate analysis revealed IHC HER2 heterogeneity as one of the independent poor prognostic factors (HR: 3.115, 95%CI: 1.610-6.024).

CONCLUSION

IHC of HER2 heterogeneity is the pivotal predictor for trastuzumab-based chemotherapy. Thus, HER2 heterogeneity should be considered during the assessment of HER2 expression.

Evaluation of Intratumoral and Intertumoral Heterogeneity of MET Protein Expression in Gastric Cancer

Tumor heterogeneity of a target molecule could contribute to failure of the targeted therapy. We investigated the heterogeneity of MET expression within same primary gastric cancer (GC) and between primary and corresponding secondary GC lesions using immunohistochemistry (IHC). Intratumoral heterogeneity was defined as discordant MET status among 3 tissue microarray cores (3 different areas of same tumor). IHC 3+ was considered positive for MET overexpression. MET overexpression was observed in 2.7% (50/1869) of all examined cores and 5.3% (33/623) of primary GCs. When we compared MET IHC results between 3 cores from each tumor, intratumoral heterogeneity was identified (65.0% in total 623 cases; 84.4% in 480 cases with any staining intensity; 84.9% in 251 cases with moderate to strong intensity; 90.9% in 33 cases with strong intensity). Of 33 MET-overexpressed GCs, the average proportion of strongly stained area was 19.6% in the whole sections. Of 269 cases with primary GC and regional lymph node metastasis, 17 (6.3%) showed MET positivity in which 9 (52.9%) were discordant (negative conversion). In 123 cases with primary and corresponding local recurrent/distant metastatic GC, 3 (2.4%) showed MET positivity in which 2 (66.7%) were discordant (positive conversion). In the survival analysis, MET IHC 3+ in lymph node metastases was an independent negative prognostic factor for overall survival. We found that MET overexpression is uncommon and highly heterogeneous in GC. This severe heterogeneity of MET status should be considered in tissue sampling and development of biomarkers for anti-MET therapy.

Claudin-18 expression in oesophagogastric adenocarcinomas: a tissue microarray study of 523 molecularly profiled cases

BACKGROUND

Claudin-18 (CLDN18) is a highly specific tight junction protein of the gastric mucosa. An isoform of CLDN18, the Claudin 18.2, has recently emerged as an innovative drug target for metastatic gastric cancer.

METHODS

We investigated the immunohistochemical profile of CLDN18, p53, p16, E-cadherin, MSH2, MSH6, MLH1, PSM2, HER2, and PDL-1 in a large series of 523 primary gastric carcinomas (GCs; n = 408) and gastro-oesophageal carcinomas (GECs; n = 115) and 135 matched and synchronous nodal metastases. The status of HER2 and EBER by means of chromogenic in situ hybridisation (CISH) was also evaluated.

RESULTS

High membranous CLDN18 expression was present in 150/510 (29.4%) primary cases and in 45/132 (34.1%) metastases. An abnormal expression (i.e. nuclear and/or cytoplasmic) was observed in 115 (22.5%) primary cases and in 33 (25.0%) metastases. A 38.8% of the cases showed significant CLDN18 intratumoural variability among the different tissue microarray cores obtained from the same tumour. Positive membrane CLDN18 expression was statistically associated with non-antral GCs (p = 0.016), Lauren diffuse type (p = 0.009), and with EBV-associated cancers (p < 0.001).

CONCLUSIONS

CLDN18 is frequently expressed in gastric and gastro-oesophageal cancers; further studies should investigate the prognostic significance of CLDN18 heterogeneity in order to implement its test into clinical practice.

A survival guide to HER2 testing in gastric/gastroesophageal junction carcinoma

Human epidermal growth factor receptor 2 (HER2) status determines gastric/gastroesophageal junction (GEJ) adenocarcinomas that benefit from targeted therapy; hence, HER2 testing has become a routine practice. Accurate HER2 testing is fundamental to select eligible patients who will benefit from HER2-targeted treatment. The reported HER2-positive rate in gastric/GEJ cancers ranges from 4.4% to 53.4%, and HER2-positive tumors are considered to have more-aggressive biologic behavior and tumor recurrence. Main modalities of HER2 testing in clinical practice include immunohistochemistry (IHC) for protein expression and in situ hybridization (ISH) for gene amplification. Many technical pitfalls affect the accuracy of HER2 result. Additionally, several issues in HER2 testing are related to the tumor biology, sample selection, interpretation of IHC and ISH results, and confirming HER2 status. Therefore, gastric/GEJ adenocarcinoma-specific HER2 testing protocols have been developed and standardized to minimize the impact of these preanalytical and analytical factors and to enhance reproducibility of HER2 testing results. This review provides up-to-date practical guidance to clinicians on accurate HER2 testing and interpretation of results in gastric/GEJ adenocarcinoma.

Validated clinico-pathologic nomogram in the prediction of HER2 status in gastro-oesophageal cancer

Background

HER2 is the only validated predictive biomarker in gastro-oesophageal carcinoma (GOC). However, several factors, such as heterogeneity in protein expression, shortage of evaluable tumour tissue and need for quick target assessment, underline the usefulness of a pre-screening tool in order to anticipate HER2 status.

Methods

Data from 723 consecutive GOC analysed for HER2 at four Italian Institutions were collected. HER2 positivity was defined as 3+ by immunohistochemistry (IHC) or 2+ with gene amplification by in situ hybridisation (ISH). A multivariate logistic regression model was built using data from 413 cases, whereas 310 patients served as validation cohort. C-index, visual inspection of the calibration plot, Brier score and Spiegelhalter z-test were used to assess the performance of the nomogram.

Results

HER2 positive rate was 17.4%. Four variables were retained after adjustment in the final model: grading, Lauren’s histotype, pathologic material analysed (surgical specimen/biopsy) and site of tissue collection (primary tumour/metastases). Visual inspection of the calibration plot revealed a very good overlap between predicted and observed probabilities, with a Brier score of 0.101 and a non-significant Spiegelhalter z-test (P = 0.319). C-index resulted in 0.827 (95%CI 0.741–0.913).

Conclusion

A simple nomogram based on always-available pathologic information accurately predicts the probability of HER2 positivity in GOC.

Tumor-specific genetic aberrations in cell-free DNA of gastroesophageal cancer patients

The applicability of liquid biopsies is studied intensively in all types of cancer and analysis of circulating tumor DNA (ctDNA) has recently been implemented clinically for mutation detection in lung cancer. ctDNA may provide information about tumor quantity and mutations present in the tumor, and as such have many potential applications in diagnosis and treatment of cancer. It has been suggested that ctDNA analysis may overcome the issue of intra-tumor heterogeneity faced by tissue biopsies and serve as an additional diagnostic tool. Furthermore, liquid biopsies are potentially helpful for monitoring of treatment response as well as detection of minimal residual disease and relapse. Gastroesophageal cancers (GEC) have high mortality rates and the majority of patients present with advanced stage at diagnosis or succumb due to disease recurrence even after radical resection of the primary tumor. Biomarkers that can help optimize treatment strategy are thus highly desirable. The present study is a review of published data on ctDNA in GEC patients. We identified 25 studies in which tumor-specific genetic aberrations were investigated in plasma or serum and discuss these in relation to the methods applied for ctDNA analysis. The methods used for ctDNA detection greatly influence the sensitivity of the analysis and, therefore, the potential clinical applications. We found that studies of ctDNA in GEC, although limited in number, are promising for several applications such as genetic profiling of tumors and monitoring of disease progression. However, more studies are needed to establish if and how this analysis can be clinically implemented.

HER2/neu (ERBB2) expression and gene amplification correlates with better survival in esophageal adenocarcinoma

BACKGROUND

HER2 (ERBB2 or HER2/neu) is a tyrosine-kinase increasing cell proliferation. Overexpression/amplification of HER2 is correlated with worse prognosis in solid malignancies. Consequently, HER2 targeting is established in breast and upper gastrointestinal tract cancer. There are conflicting data concerning the impact of HER2 overexpression on esophageal adenocarcinoma (EAC), as most studies do not differ between cancers of the esophagus/gastroesophageal junction and the stomach. The aim of this study was to analyze the expression/amplification of HER2 in EAC in correlation to clinicopathological data to verify its prognostic impact.

METHODS

We analyzed 428 EAC patients that underwent transthoracic thoraco-abdominal esophagectomy between 1997 and 2014. We performed HER2 immunohistochemistry (IHC) according to the guidelines and fluorescence-in-situ-hybridization (FISH) for IHC score2+, using tissue micro arrays (TMA) with up to eight biopsies from the surface and infiltration area of a single tumor for evaluating HER2-heterogeneity and single-spot TMA. The HER2-status was correlated with clinicopathological data.

RESULTS

HER2-positivity was found in up to 14.9% in our cohort (IHC score 3+ or IHC score 2+ with gene amplification) and demonstrated a significantly better overall survival (OS) in correlation to HER2-negative tumors (median OS 70.1 vs. 24.6 months, p = 0.006). HER2-overexpression was more frequently seen in lower tumor stages (pT1/pT2, p = 0.038), in the absence of lymphatic metastases (pN0/pN+, p = 0.020), and was significantly associated with better histological grading (G1/G2) (p = 0.041).

CONCLUSION

We demonstrated a positive prognostic impact of HER2 overexpression in a large cohort of EAC, contrary to other solid malignancies including gastric cancer and breast cancer, but consistent to the results of a large study on EAC from 2012.

Changes in HER2 Expression and Amplification Status Following Preoperative Chemotherapy for Gastric Cancer

BACKGROUND

It is essential to establish a strategy for second-line treatment for human epidermal growth factor receptor 2 (HER2)-positive gastric cancer; however, HER2 expression status after chemotherapy treatment is not routinely determined.

MATERIALS AND METHODS

We analyzed 25 cases of gastric cancer that received preoperative chemotherapy and selected the six pre-treatment samples that were HER2-positive. Pre- and post-treatment tumor samples were examined for HER2 expression, and for HER2, epidermal growth factor receptor (EGFR), and hepatocyte growth factor receptor (MET) gene amplification.

RESULTS

Three patients had been treated with trastuzumab plus chemotherapy, and three patients with cytotoxic chemotherapy alone. Only one case that had an initial HER2 score of 3+ and had received trastuzumab plus chemotherapy remained HER2-positive after treatment. Decrease or loss of HER2 expression and amplification was observed in the other five patients. Amplification of EGFR or MET was not observed in any pre- or post-treatment specimens.

CONCLUSION

Our data suggest that trastuzumab plus chemotherapy or chemotherapy alone may induce loss of HER2 positivity.

Clinicopathological features and endoscopic findings of HER2-positive gastric cancer

BACKGROUND

Human epidermal growth factor receptor 2 (HER2) expression in gastric cancer is highly heterogeneous. Therefore, it is important to take endoscopic samples from appropriate tumor sites.

METHODS

Between January 2008 and April 2015, patients with gastric or gastroesophageal junction cancer with histologically confirmed adenocarcinoma were included. Surgical samples or endoscopic biopsy samples were examined for HER2 using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). Tissues were considered to be HER2 positive when either assessment revealed either an IHC score of 3+ or an IHC score of 2+ accompanied by a positive FISH result. Endoscopic findings were retrieved in all cases where available, and we examined the portion from which a biopsy was obtained.

RESULTS

Out of the 612 patients included in the study, 104 (17%) were HER2 positive. The proportion of HER2-positive gastric tumors with differentiated (vs. undifferentiated) histology was significantly higher (29 vs. 6%, respectively; p < 0.001). The HER2-positive rate of papillary adenocarcinomas (vs. tubular) was particularly high (62%, 8/13; p = 0.023). The proportion of HER2-positive gastric tumors of Borrmann classification 0 or 1 was significantly higher than that of tumors of classified as 2, 3, or 4 (45 vs. 16%, respectively; p < 0.001). The HER2-positive rates per biopsy specimen from the superficial spreading portion, ulcer mound, ulcer bed, and mass portion were 100, 91, 45, and 100%, respectively.

CONCLUSIONS

HER2-positive gastric cancer tends to be associated with a differentiated histology, particularly papillary adenocarcinoma, and a Borrmann classification of 0 or 1 tumors. Based on these endoscopic findings, it is important to recognize the superficial spreading portion and the mass portion of gastric malignancies.

HER2 Heterogeneity in Gastroesophageal Cancer Detected by Testing Biopsy and Resection Specimens

CONTEXT

- In advanced gastric, esophageal, and gastroesophageal junction adenocarcinomas (GE-GEJ-AC) that overexpress ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2), anti-HER2 monoclonal antibody therapy confers survival benefit. To select patients for treatment, HER2 expression and gene amplification are evaluated by immunohistochemistry (IHC) and in situ hybridization.

OBJECTIVE

- To determine whether GE-GEJ-AC tested for HER2 on biopsy specimens of a primary tumor show different IHC scores and/or HER2 amplification by in situ hybridization in matched resection specimens, potentially changing therapy eligibility.

DESIGN

- Immunohistochemistry and silver in situ hybridization were performed in biopsy and/or resection specimens from 100 patients. HER2 testing was performed in matched resection and biopsy specimens of 15 cases to determine whether GE-GEJ-AC with IHC scores of 0, 1⁺, and 2⁺ in biopsy and resection specimens had different IHC and silver in situ hybridization results.

RESULTS

- The IHC 3⁺ cases showed HER2 amplification in 4 of 5 cases (80%), and IHC scores of 0, 1⁺, and 2⁺ showed 3.5%, 14.3%, and 23.5% HER2 amplification by silver in situ hybridization. Among the 15 paired biopsy and resection specimens, 9 (60%) had at least pT2 stage GE-GEJ-AC with HER2 IHC scores of 0, 1⁺, or 2⁺ in the biopsy, and 2 of those 9 cases (22%) had IHC 3⁺ and HER2 amplification by silver in situ hybridization on the resection specimen.

CONCLUSIONS

- Our data suggest that HER2 testing should be repeated on resection specimens of GE-GEJ-AC with HER2 IHC scores of negative (0 and 1⁺) or equivocal (2⁺) and in situ hybridization amplification negative biopsy specimen results to evaluate for HER2 heterogeneity when patients are being considered for anti-HER2 therapy.

Tumor containing fragment number influences immunohistochemistry positive rate of HER2 in biopsy specimens of gastric cancer

Background

HER2 assessment in biopsy specimens of gastric cancer (GC) is challenging because of the intratumoral heterogeneity. False negative results may be get because of limited biopsy material. The aim of this study is to explore how tumor-containing fragment number and biopsy specimen number affect HER2 immunohistochemistry (IHC) positive rate.

Methods

Eight hundred and ninety biopsy specimens and 459 paired resected specimens were collected. IHC staining of HER2 was performed. HER2 IHC positive (scored 3+) rate was compared based on tumor-containing fragment number, biopsy specimen number, average size and tumor tissue proportion of tumor-containing fragments. The positive predictability of biopsy specimens to resected specimens was analyzed based on tumor fragment number.

Results

HER2 IHC positive rates were 2.0, 3.5, 7.0, 13.2, 17.1, and 15.9% when tumor fragment numbers were 1, 2, 3, 4, 5 and 6 respectively. The rate rose with the increase of tumor fragment number (P = 0.004). ROC curve analysis showed that biopsy specimens exhibited positive predictability when tumor fragment number reached 3, but showed better performance when the number was ≥4 (P < 0.05). After fragment number reached 4, no statistic differences were reached in either HER2 IHC positive rate or positive predictability with further increase of the number (P > 0.05). HER2 IHC positive rate was not associated with biopsy number (P = 0.127), average size of tumor fragments (P = 0.397), and tumor tissue proportion of tumor fragments (P = 0.825) directly.

Conclusions

The number of tumor-containing fragments influences HER2 IHC positive (scored 3+) rate. Greater than or equal to 4 (≥4) tumor fragments give better results in the positive rate as well as positive predictability. We recommend the number of tumor containing fragments be described in the HER2 IHC pathology reports for clinical reference in endoscopic biopsy specimens of GC.

HER2 testing in gastric cancer: results of a German expert meeting

Valid HER2 testing is essential for optimal therapy of patients with HER2-positive gastric cancer and the correct use of first-line chemotherapy. While testing for HER2 status in breast cancer is routinely performed, this is not the case for HER2 testing in gastric cancer and it is usually only performed on clinician request. An interdisciplinary German expert group (pathologists and clinicians) took the challenges of HER2 testing in gastric cancer as an opportunity to address essential aspects and questions for the practical use of HER2 testing in this indication. The recommendations made in this manuscript reflect the consensus of all participants and reflect their opinions and long-term experience in this field.

HER2 Testing and Clinical Decision Making in Gastroesophageal Adenocarcinoma: Guideline From the College of American Pathologists, American Society for Clinical Pathology, and the American Society of Clinical Oncology

Context ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2) is currently the only biomarker established for selection of a specific therapy for patients with advanced gastroesophageal adenocarcinoma (GEA). However, there are no comprehensive guidelines for the assessment of HER2 in patients with GEA. Objectives To establish an evidence-based guideline for HER2 testing in patients with GEA, formalize the algorithms for methods to improve the accuracy of HER2 testing while addressing which patients and tumor specimens are appropriate, and to provide guidance on clinical decision making. Design The College of American Pathologists (CAP), American Society for Clinical Pathology (ASCP), and the American Society of Clinical Oncology (ASCO) convened an Expert Panel to conduct a systematic review of the literature to develop an evidence-based guideline with recommendations for optimal HER2 testing in patients with GEA. Results The Panel is proposing 11 recommendations with strong agreement from the open comment participants. Recommendations The Panel recommends that tumor specimen(s) from all patients with advanced GEA, who are candidates for HER2-targeted therapy, should be assessed for HER2 status before the initiation of HER2-targeted therapy. Clinicians should offer combination chemotherapy and an HER2-targeted agent as initial therapy for all patients with HER2-positive advanced GEA. For pathologists, guidance is provided for morphologic selection of neoplastic tissue, testing algorithms, scoring methods, interpretation and reporting of results, and laboratory quality assurance. Conclusion This guideline provides specific recommendations for assessment of HER2 in patients with advanced GEA while addressing pertinent technical issues and clinical implications of the results.

HER2 Testing and Clinical Decision Making in Gastroesophageal Adenocarcinoma: Guideline From the College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology

CONTEXT

- ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2) is currently the only biomarker established for selection of a specific therapy for patients with advanced gastroesophageal adenocarcinoma (GEA). However, there are no comprehensive guidelines for the assessment of HER2 in patients with GEA.

OBJECTIVES

- To establish an evidence-based guideline for HER2 testing in patients with GEA, to formalize the algorithms for methods to improve the accuracy of HER2 testing while addressing which patients and tumor specimens are appropriate, and to provide guidance on clinical decision making.

DESIGN

- The College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology convened an expert panel to conduct a systematic review of the literature to develop an evidence-based guideline with recommendations for optimal HER2 testing in patients with GEA.

RESULTS

- The panel is proposing 11 recommendations with strong agreement from the open-comment participants.

RECOMMENDATIONS

- The panel recommends that tumor specimen(s) from all patients with advanced GEA, who are candidates for HER2-targeted therapy, should be assessed for HER2 status before the initiation of HER2-targeted therapy. Clinicians should offer combination chemotherapy and a HER2-targeted agent as initial therapy for all patients with HER2-positive advanced GEA. For pathologists, guidance is provided for morphologic selection of neoplastic tissue, testing algorithms, scoring methods, interpretation and reporting of results, and laboratory quality assurance.

CONCLUSIONS

- This guideline provides specific recommendations for assessment of HER2 in patients with advanced GEA while addressing pertinent technical issues and clinical implications of the results.

HER2 Testing and Clinical Decision Making in Gastroesophageal Adenocarcinoma: Guideline From the College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology

CONTEXT

ERBB2 (erb-b2 receptor tyrosine kinase 2 or HER2) is currently the only biomarker established for selection of a specific therapy for patients with advanced gastroesophageal adenocarcinoma (GEA). However, there are no comprehensive guidelines for the assessment of HER2 in patients with GEA.

OBJECTIVES

To establish an evidence-based guideline for HER2 testing in patients with GEA, to formalize the algorithms for methods to improve the accuracy of HER2 testing while addressing which patients and tumor specimens are appropriate, and to provide guidance on clinical decision making.

DESIGN

The College of American Pathologists, American Society for Clinical Pathology, and American Society of Clinical Oncology convened an expert panel to conduct a systematic review of the literature to develop an evidence-based guideline with recommendations for optimal HER2 testing in patients with GEA.

RESULTS

The panel is proposing 11 recommendations with strong agreement from the open-comment participants.

RECOMMENDATIONS

The panel recommends that tumor specimen(s) from all patients with advanced GEA, who are candidates for HER2-targeted therapy, should be assessed for HER2 status before the initiation of HER2-targeted therapy. Clinicians should offer combination chemotherapy and a HER2-targeted agent as initial therapy for all patients with HER2-positive advanced GEA. For pathologists, guidance is provided for morphologic selection of neoplastic tissue, testing algorithms, scoring methods, interpretation and reporting of results, and laboratory quality assurance.

CONCLUSIONS

This guideline provides specific recommendations for assessment of HER2 in patients with advanced GEA while addressing pertinent technical issues and clinical implications of the results.

HER2 heterogeneity in gastric/gastroesophageal cancers: From benchside to practice

HER2 is overexpressed in approximately 10%-20% of gastric and gastroesophageal junction carcinomas. In these types of cancer, accurate assessment of HER2 status is mandatory, for selecting patients who may benefit from targeted therapies with anti-HER2 drugs such as Trastuzumab. This manuscript focuses on HER2 in gastric carcinogenesis, on optimal evaluation of HER2 and on the possible causes which may contribute to inaccurate HER2 evaluation. Similarly to breast cancer HER2 evaluation, standardization of HER2 testing in gastric cancer is necessary in diagnostic practice. The three principle aspects which require consideration are: (1) the choice of sample with regards to cancer morphology - intestinal vs diffuse areas; (2) the choice of scoring criteria - use of HER2 scoring criteria specific for gastric cancer; and (3) the choice of HER2 evaluation methods - use of an algorithm in which both immunohistochemistry and in situ hybridization play a role. Problematic issues include: (1) pre-analytic variables with particular emphasis on fixation; (2) recommended methodology for HER2 assessment (immunohistochemistry vs in situ hybridization); (3) HER2 heterogeneity both within the primary tumor and between primary tumor and metastases; (4) reliability of biopsies in HER 2 evaluation; and (5) quantity of sample (FFPE blocks from surgical specimens or endoscopic biopsies) necessary for an adequate assessment.

Clinical impact of tumour biology in the management of gastroesophageal cancer

The characterization of oesophageal and gastric cancer into subtypes based on genotype has evolved in the past decade. Insights into the molecular landscapes of gastroesophageal cancer provide a roadmap to assist the development of new drugs and their use in combinations, for patient stratification, and for trials of targeted therapies. Trastuzumab is the only approved treatment for gastroesophageal cancers that overexpress HER2. Acquired resistance usually limits the duration of response to this treatment, although a number of new agents directed against HER2 have the potential to overcome or prolong the time until resistance occurs. Beyond that, anti-VEGFR2 therapy with ramucirumab was the first biological treatment strategy to produce a survival benefit in an unselected population of patients with chemotherapy-refractory gastroesophageal cancer. Large initiatives are starting to address the role of biomarker-driven targeted therapy in the metastatic and in the perioperative setting for patients with this disease. Immunotherapy also holds promise, and our understanding of subsets of gastroesophageal cancer based on patterns of immune response continues to evolve. Efforts are underway to identify more relevant genomic subsets through genomic screening, functional studies, and molecular characterization. Herein, we provide an overview of the key developments in the treatment of gastroesophageal cancer, and discuss potential strategies to further optimize therapy by targeting disease subtypes.