Human Epidermal Growth Factor Receptor 2-Positive Duodenal Adenocarcinoma: A Case Report and Review of the Literature

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.

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.

A HER2-mutant patient with late-stage duodenal adenocarcinoma benefited from anti-HER2 therapy and PD-1 inhibition: a case report

Duodenal adenocarcinoma (DA) is a subtype of small bowel adenocarcinoma (SBA). Compared with gastrointestinal cancers such as colorectal cancer and gastric cancer, SBA is less common. For patients with advanced and metastatic DA, chemotherapies are usually extrapolated from colorectal cancer and gastric cancer but the therapeutic effects remain undefined. Herein, we reported a 50-year-old female patient whom was diagnosed as stage IV DA with metastasis to both lungs and retroperitoneal lymph nodes. The next generation sequencing (NGS) using a panel consisting of 168 cancer related genes revealed amplification of the HER2/ERBB2 gene which has been a well-recognized therapeutic target among various tumor types. The anti-HER2 targeted therapy trastuzumab was used in combination with XELOX (oxaliplatin and capecitabine) as the first line treatment. The patient achieved partial response (PR) and had progression-free survival (PFS) of six months. After progressive disease (PD), the patient started the second line treatment with trastuzumab and PD1 inhibitors and remained stable disease (SD) with PFS for three months. The use of trastuzumab in neoadjuvant and adjuvant settings have been reported in sporadic cases. To the best of our knowledge, it is the first report to use anti-HER2 therapy and PD-1 inhibition as systemic therapy for advanced DA patients.

Beyond bevacizumab: a review of targeted agents in metastatic small bowel adenocarcinoma

Small bowel cancers are rare tumors with an incidence 50-100-fold less than colorectal cancer. These tumors carry a poor prognosis. Owing to its rarity, treatment of this disease, particularly in its advanced stages, has not been optimized and is derived mainly from treatment regimens for colorectal cancer. Based on recent studies bevacizumab, an antibody directed against vascular endothelial growth factor and used in the management of metastatic CRC, has been added to treatment guidelines for metastatic small bowel adenocarcinoma. We investigate in this review the evidence behind other targeted treatments that may be beneficial in the treatment of metastatic small bowel adenocarcinoma. These are agents against EGFR, VEGFR-2, HER2, and NTRK as well as immune checkpoint inhibitors. The last class of drugs appears to hold the greatest promise based on the preponderance of evidence supporting its use. However, overall data remains sparse. Results of studies currently underway will be valuable in shedding more light on the management of this aggressive cancer.