HER2-low in gastro-oesophageal adenocarcinoma: a real-world pathological perspective

HER2-low across solid tumours: different incidences and definitions

Antibody-drug conjugates, particularly trastuzumab deruxtecan (T-DXd), have emerged as effective therapies for various solid tumours. Clinical trials show that T-DXd improves survival in both HER2-positive and HER2-low breast cancer patients. Additionally, it improves survival in HER2-positive gastro-oesophageal cancer and elicits objective responses in HER2-low tumours. Responses have also been noted in lung and gynaecological cancers with HER2 expression, although subgroup analyses for HER2-low cases are lacking. This review assesses HER2 protein expression levels and gene amplification across solid tumours where T-DXd shows potential benefits. We focus on the accuracy and limitations of HER2 testing methods, particularly for identifying HER2-low cancer. A semi-systematic approach was employed, searching EMBASE, Medline, Cochrane, and PubMed databases. We calculated median incidences of HER2-positive, HER2-low, and HER2-0 by immunohistochemistry (IHC), and HER2 amplification by in situ hybridisation (ISH). A total of 144 studies were included, covering breast (n=57), gastro-oesophageal (n=33), lung (n=17), gynaecological (n=24), and various other carcinomas (n=13). The median incidences of HER2-low were 52%, 16%, 58%, and 17% in breast, gastro-oesophageal, endometrial, and ovarian cancers, respectively, with unknown incidences in lung and cervical cancers. Factors influencing HER2-low detection include tumour heterogeneity, antibody clones, observer variability, and lack of validated scoring criteria. Given the significant proportion of HER2-low cases, many patients could benefit from T-DXd, but limitations in detection accuracy necessitate further research and standardisation in diagnostic methods and criteria to advance the clinical utility of T-DXd for HER2-low tumours.

Heterogeneity of predictive biomarker expression in gastric and esophago-gastric junction carcinoma with peritoneal dissemination

BACKGROUND

Temporal and spatial molecular heterogeneity contributes to resistance to targeted and immune therapies in gastric and esophagogastric junction carcinoma (G/EGJ). This study evaluates differences in biomarker expression between primary G/EGJ and paired peritoneal metastases (PM).

METHODS

We analyzed 74 cases of primary G/EGJ and paired PM using immunohistochemistry for HER2, PD-L1, Claudin18 (CLDN18), DNA mismatch repair (MMR) proteins, p53, E-cadherin, and in situ hybridization for EBER. Biomarker concordance between primary and metastatic tumors was assessed.

RESULTS

Primary G/EGJ were predominantly poorly cohesive (45.9%) or mixed-type (37.8%). Regarding predictive biomarkers, low rates of HER2 overexpression (5.4%), MMR deficiency (4.1%), and EBER positivity (1.4%) were observed, while PD-L1 CPS ≥ 1 occurred in 79.7% of cases and CLDN18 positivity was observed in 31.1% of cases. Concordance was perfect for MMR and EBER, while PD-L1 showed the highest discordance (32.4%). HER2 had a low discordance rate (2.7%). CLDN18 exhibited good concordance (86.5%) and showed consistent positivity in PD-L1- and HER2-negative primary tumors (28.6%).

CONCLUSION

G/EGJ with PM show distinct molecular features and spatial heterogeneity, with MMR, EBER, and HER2 demonstrating strong concordance, while PD-L1 showed greater variability. As for novel biomarkers, CLDN18.2 shows substantial concordance between primary G/EGJ and PM and could be a promising target in HER2/PD-L1-negative G/EGJ with PM.

Expression of therapy target molecules in esophagogastric junction and Barrett's adenocarcinoma

BACKGROUND

Recently, novel molecular targeted therapies have been developed for gastric and esophageal adenocarcinomas. We examined the status of therapeutic target molecules in esophagogastric junction (EGJ) and Barrett's adenocarcinoma.

METHODS

Tissue microarrays were constructed from 114 cases of non-Barrett's EGJ adenocarcinoma and 30 cases of Barrett's adenocarcinoma. Immunohistochemistry for mismatch repair proteins, PD-L1, HER2, CLDN18, FGFR2b, and EBER-ISH was performed. When HER2 immunohistochemistry was 2 + , gene amplification was examined using in situ hybridization.

RESULTS

EBER positivity, mismatch repair deficiency, PD-L1 combined positive score (CPS) ≥ 1, CLDN18 expression ≥ 75%, FGFR2b expression, and HER2 positivity were observed in 7 (6.1%), 11 (9.6%), 70 (61.4%), 38 (33.3%), 6 (5.3%), and 11 (9.6%) cases of EGJ adenocarcinoma as well as in 0 (0%), 0 (0%), 23 (76.7%), 7 (23.3%), 2 (6.7%), and 6 (20.0%) cases of Barrett's adenocarcinoma, respectively. PD-L1 CPS ≥ 1 cases had longer recurrence-free survival (P = 0.001) and overall survival (P = 0.003) than CPS < 1 cases. Other target molecules were not associated with survival. A total of 93/114 (81.6%) cases of EGJ adenocarcinoma and 26/30 (86.7%) cases of Barrett's adenocarcinomas expressed at least one target molecule.

CONCLUSIONS

Most EGJ and Barrett's adenocarcinomas may be eligible for molecular targeted therapy. Appropriate patient stratification based on these molecular tests will be important for precision medicine of the EGJ and Barrett's adenocarcinoma.

Nationwide survey on HER2 and PD-L1 testing practices in gastric cancer across Japan

BACKGROUND

Since HER2 and PD-L1 testing are key to selecting drugs for first-line treatments in advanced gastric cancer, evaluating differences in these tests among institutions is necessary to standardize treatment.

METHODS

A questionnaire survey was conducted targeting institutions certified by the Japanese Gastric Cancer Association.

RESULTS

Responses were obtained from 155 institutions. Most institutions performed HER2 testing in-house, while PD-L1 tests were largely outsourced. HER2 scores and PD-L1 CPS rates showed greater variability across institutions than anticipated. In the pre-analytic phase, 10% neutral buffered formalin was commonly used, with fixation practices generally following guidelines. Overall, the impact of fixation-related factors was limited, but in surgical specimens, longer fixation was associated with a higher proportion of score 0/1+ and a lower proportion of score 3+. When examining HER2 scores by institution, if a particular score had a high (or low) frequency in biopsy, the same trend was also seen in surgical specimens.

CONCLUSIONS

These findings suggest that not only factors related to specimen preparation, but also biases in evaluation criteria among pathologists may contribute to the significant variability among institutions. Standardization of pre- and post-analytic phases, coupled with appropriate training, is essential to achieve consistent gastric cancer therapy.

Pre-Surgical Endoscopic Biopsies Are Representative of Esophageal and Esophago-Gastric Junction Adenocarcinoma Histologic Classes and Survival Risk

Background and Objectives: The Esophageal Adenocarcinoma Study Group Europe (EACSGE) recently proposed a granular histologic classification of esophageal-esophago-gastric junctional adenocarcinomas (EA-EGJAs) based on the study of naïve surgically resected specimens that, when combined with the pTNM stage, is an efficient indicator of prognosis, molecular events, and response to treatment. In this study, we compared histologic classes of endoscopic biopsies taken before surgical resection with those of the surgical specimen, to evaluate the potential of the EACSGE classification at the initial diagnostic workup. Methods: A total of 106 EA-EGJA cases with available endoscopic biopsies and matched surgical resection specimens were retrieved from five Italian institutions. Histologic classification was performed on all specimens to identify well-differentiated glandular adenocarcinoma (WD-GAC), poorly differentiated glandular adenocarcinoma (PD-GAC), mucinous muconodular carcinoma (MMC), infiltrative mucinous carcinoma (IMC), diffuse desmoplastic carcinoma, diffuse anaplastic carcinoma (DAC), and mixed subtypes. Related risk subgroups (low-risk versus high-risk) were also assessed. The correlations of histologic classes and risk subgroups between diagnostic biopsies and surgical resection specimens were explored with Spearman's correlation test. Sensitivity, specificity, accuracy, positive predictive value, negative predictive value, true positives, true negatives, false positives, and false negatives were also calculated. Results: A strong positive correlation between biopsies and surgical specimens occurred for both histologic classes (coefficient: 0.75, p < 0.001) and risk subgroups (coefficient: 0.65, p < 0.001). The highest sensitivities and specificities were observed for MMC, IMC, and DAC (100% and 99% for all), followed by WD-GAC (sensitivity 91%, specificity 79%) and PD-GAC (sensitivity 722%, specificity 86%). The low-risk and high-risk groups presented a sensitivity and specificity of 89% and 76% (low-risk) and 76% and 89% (high-risk). Conclusions: The EACSGE histologic classification of EA-EGJAs and associated prognostic subgroups can be reliably assessed on pre-operative diagnostic biopsies. Further studies on larger and more representative cohorts of EA-EGJAs will allow us to validate our findings and confirm if the EA-EGJA biopsy histomorphology and clinical TNM staging will be as efficient as the surgical specimen histomorphology and pTNM in predicting patient prognoses and tailoring personalized therapeutic approaches.

Clinicopathological and prognostic significance of HER2-low expression in advanced gastric cancer: a retrospective observational study

PURPOSE

Human epidermal growth factor receptor 2 (HER2) status is a critical biomarker in advanced gastric cancer (AGC). While the role of HER2-positive tumors in guiding targeted therapies is well-established, the clinical implications of HER2-low expression, defined as immunohistochemistry (IHC) 1+ or IHC 2+/in situ hybridization-negative (ISH-negative), remain undetermined. The aim of this study was to investigate the prognostic significance and clinicopathological features of HER2-low AGC.

PATIENTS AND METHODS

This retrospective analysis involved patients with AGC treated with first-line fluoropyrimidine and platinum-based chemotherapy from 2011 to 2020. Patients were categorized into HER2-zero (HER2 IHC 0), HER2-low (IHC 1+ or 2+/ISH-negative), and HER2-positive (IHC 2+/ISH-positive or 3+) groups.

RESULTS

Among 548 patients analyzed, 33.0%, 45.1%, and 21.8% were classified as HER2-zero, HER2-low, and HER2-positive, respectively. The proportions of male patients, intestinal-type histology, esophagogastric junction/cardia involvement, metastatic disease status, ≥2 metastatic sites, liver metastasis, lymph node metastasis, and high serum carcinoembryonic antigen levels were gradually elevated in the HER2-zero, HER2-low, and HER2-positive groups. Overall survival (median) was 13.8, 13.6, and 23.0 months, respectively, with a non-significant trend favoring HER2-positive over HER2-low (adjusted hazard ratio: 0.80; P = .0672). A delayed separation of Kaplan-Meier curves for overall survival between the HER2-zero and HER2-low groups was observed, without reaching statistical significance (adjusted hazard ratio: 1.12; P = .2568).

CONCLUSION

Patients with HER2-low status exhibited intermediate and specific clinicopathological features within the HER2-negative category. In terms of prognosis, HER2-low patients showed a worsening trend compared with HER2-positive patients. This evidence implies that HER2-low status represents a distinct clinical subset, bridging the gap between the HER2-zero and HER2-positive profiles.

Claudin-18.2 Immunohistochemical Evaluation in Gastric and Gastroesophageal Junction Adenocarcinomas to Direct Targeted Therapy: A Practical Approach

Claudin-18.2 (CLDN18.2) expression evaluated by immunohistochemistry is a new biomarker for gastric and gastroesophageal junction adenocarcinomas that will soon have market authorization for implementation into routine clinical practice. Despite successful testing in the setting of clinical trials, no specific practical testing guidelines have been proposed. Several preanalytical and analytical variables may interfere with adequate CLDN18.2 staining interpretation; thus, this article provides practical guidance on CLDN18.2 testing and scoring in gastric and gastroesophageal junction adenocarcinomas to identify patients who may respond to targeted therapy with monoclonal antibodies directed against CLDN18.2. Based on available data, moderate to strong (2+/3+) membrane staining in ≥75% of adenocarcinoma cells is the proposed cutoff for clinical use of monoclonal antibody anti-CLDN18.2 (zolbetuximab).

Prognostic and Predictive Roles of HER2 Status in Non-Breast and Non-Gastroesophageal Carcinomas

The oncogene ERBB2, also known as HER2 or c-ERB2, is located on chromosome 17 (q12). It encodes a tyrosine kinase receptor, the human epidermal growth factor receptor 2 (HER2), involved in neoplastic proliferation, tumor angiogenesis, and invasiveness. Over the past years, the introduction of various anti-HER2 therapies has significantly improved outcomes for patients with HER2-positive breast and gastroesophageal carcinomas. More recently, the introduction of a new antibody-drug conjugate, that is trastuzumab deruxtecan, expanded the therapeutic options to low-HER2 breast and gastroesophageal tumors. HER2 protein overexpression is investigated using immunohistochemistry, gene amplification using fluorescence in situ hybridization, and gene mutation using next-generation sequencing. This review evaluated the predictive and prognostic role of HER2 status in various types of epithelial malignant cancers beyond breast and gastroesophageal cancers. We critically analyzed the key published studies, focusing on utilized scoring systems and assays used, and analyzed clinical parameters and therapeutic approaches. Although the evidence about prognostic and predictive roles of HER2 in carcinomas other than breast and gastroesophageal has been widely increasing over the last decade, it still remains investigational, revealing a tumor site-related prognostic and predictive value of the different types of HER2 alterations. However, standardized and validated scoring system assays have not been well-established for many organs.

Prognostic and predictive role of YKL-40 in anal squamous cell carcinoma: a serological and tissue-based analysis in a multicentric cohort

Introduction

Anal squamous cell carcinoma (ASC) is a rare gastrointestinal malignancy showing an increased incidence over the past decades. YKL-40 is an immune modulator and pro-angiogenetic factor that showed a promising prognostic and predictive potential in several malignancies, but limited data are available for ASC. This study aims to provide an extensive evaluation of the prognostic and predictive role of YKL-40 in a multicenter cohort of ASC patients.

Methods

We retrospectively retrieved 72 consecutive cases of ASC diagnosed between February 2011 and March 2021. Both serum and tissue protein expression of YKL-40 were assessed, the latter in ASC tumor cells and peritumor immune cells.

Results

Increased YKL-40 serum levels at the time of diagnosis were associated with older age (p = 0.035), presence of cardiovascular/metabolic comorbidities (p = 0.007), and death for any cause (p = 0.011). In addition, high serum levels of YKL-40 were associated with a poor prognosis (HR: 2.82, 95% CI: 1.01-7.84; p = 0.047). Protein expression of YKL-40 in ASC tumor cells was significantly associated with low tumor grade (p = 0.031), while the increased expression in peritumor immune cells was associated with a worse response of patients to chemoradiotherapy (p = 0.007). However, YKL-40 protein expression in ASC tumor cells or peritumor immune cells did not significantly impact patient overall survival.

Discussion

In conclusion, YKL-40 resulted a relevant prognostic (serum level) and predictive (tissue protein expression in peritumor immune cells) biomarker and can considerably improve ASC patient clinical management.

HER2 evaluation for clinical decision making in human solid tumours: pearls and pitfalls

The significant clinical benefits of human epidermal growth factor receptor 2 (HER2)-targeted therapeutic agents have revolutionized the clinical treatment landscape in a variety of human solid tumours. Accordingly, accurate evaluation of HER2 status in these different tumour types is critical for clinical decision making to select appropriate patients who may benefit from life-saving HER2-targeted therapies. HER2 biomarker scoring criteria is different in different organ systems, and close adherence to the corresponding HER2 biomarker testing guidelines and their updates, if available, is essential for accurate evaluation. In addition, knowing the unusual patterns of HER2 expression is also important to avoid inaccurate evaluation. In this review, we discuss the key considerations when evaluating HER2 status in solid tumours for clinical decision making, including tissue handling and preparation for HER2 biomarker testing, as well as pathologist's readout of HER2 testing results in breast carcinomas, gastroesophageal adenocarcinomas, colorectal adenocarcinomas, gynaecologic carcinomas, and non-small cell lung carcinomas.

Gastric Carcinoma in Autoimmune Gastritis: A Histopathologic and Molecular Study

Patients with autoimmune gastritis (AIG) have a 13-fold risk of developing type-1 neuroendocrine tumors, whereas the risk for gastric adenocarcinoma is still uncertain. Here we describe the clinicopathologic and molecular features of a series of gastric carcinomas (GC) arising in the context of AIG. A total of 26 AIG-associated GC specimens were collected from 4 Italian Institutions. Immunohistochemistry for MUC1, MUC2, MUC5AC, MUC6, CDX2, HER2, PD-L1, CLDN18, mismatch repair (MMR) proteins, and p53 and EBV-encoded RNA (EBER) in situ hybridization were performed. Histologic and immunohistochemical features were jointly reviewed by 5 expert gastrointestinal pathologists. Next-generation sequencing analysis (TrueSight Oncology 500, Illumina) of 523 cancer-related genes was performed on 19 cases. Most tumors were diagnosed as pT1 (52%) and they were located in the corpus/fundus (58%) and associated with operative link for gastritis assessment stage II gastritis (80.8%), absence of parietal cells, complete intestinal metaplasia, and enterochromaffin-like-cell micronodular hyperplasia. Only 4 (15.4%) GCs were diagnosed during follow-up for AIG. The following histotypes were identified: 20 (77%) adenocarcinomas; 3 (11%) mixed neuroendocrine-non-neuroendocrine neoplasms, and 2 (8%) high-grade solid adenocarcinomas with focal neuroendocrine component, 1 (4%) adenocarcinoma with an amphicrine component. Overall, 7 cases (27%) showed MMR deficiency, 3 (12%) were positive (score 3+) for HER2, 6 (23%) were CLDN18 positive, and 11 (42%) had PD-L1 combined positive score ≥ 10. EBER was negative in all cases. Molecular analysis revealed 5/19 (26%) microsatellite instability (MSI) cases and 7 (37%) tumor mutational burden (TMB) high. The most frequently altered genes were TP53 (8/19, 42%), RNF43 (7/19, 37%), ERBB2 (7/19, 37% [2 amplified and 5 mutated cases]), ARID1A (6/19, 32%), and PIK3CA (4/19, 21%). In summary, AIG-associated GCs are often diagnosed at low stage in patients with longstanding misrecognized severe AIG; they often display a neuroendocrine component or differentiation, have relatively higher rates of MMR deficiency, and TMB high.

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.

Association of PD-L1 Expression with Clinicopathologic Characters in Gastric Cancer: A Comprehensive Meta-analysis

PURPOSE

The expression level of programmed death ligand-1(PD-L1) in patients with gastric cancer is the key to determining the use of immune drugs. The relationship between PD-L1 expression level and clinical characteristics is worth exploring.

METHODS

By setting the search terms correlated to PD-L1 and gastric cancer, a nearly comprehensive search was carried out in four major databases, and the deadline for searching was September 1, 2022. The retrieved documents were further screened by strict inclusion and exclusion criteria after removing the duplication. Next, the quality of the included studies was evaluated with the Newcastle-Ottawa Scale (NOS) scale. Finally, the STATA15.1 software was used to process data and draw plots, and the odds ratios (ORs) were adopted to assess the pooled effect size.

RESULTS

A total of 85 works of literature were included in this study through screening strictly, and detailed data were extracted after evaluating the quality of the literature. The process of analysis was conducted in the whole population, Asia-Africa population, European and American population, and Asian population with CPS≥1, amd all found that the expression of PD-L1 in gastric cancer was correlated with age, tumor size, EBV infection, Her-2 expression and microsatellite status. However, the subgroup of the region also found some differences in Asian and Western regions, which was interesting and worth studying further. The included research of this study did not have significant publish bias.

CONCLUSION

After careful analysis, this study found that age (>60 years), tumor size (>5cm), EBV infection (+), Her-2 expression (+), microsatellite status (MSI), and mismatch repair status (dMMR) were risk factors for positive expression of PD-L1 in gastric cancer.