Targeted therapy for HER2-positive esophageal adenocarcinoma

HER2-positive esophageal adenocarcinoma represents a biologically distinct group of tumors driven by amplification or overexpression of the ERBB2 gene. Identifying this alteration can expand treatment options, particularly for patients with unresectable, recurrent, or metastatic disease.

The treatment landscape has developed through evidence from esophagogastric junction and gastric cancer studies, alongside smaller studies focused specifically on esophageal adenocarcinoma. As a result, therapeutic decisions require careful attention to tumor location, biomarker results, prior treatment, regulatory approvals, and the patient’s overall condition.

The scientific discussions promoted through the International Society for Diseases of the Esophagus provide an important setting for reviewing advances in molecular diagnosis, systemic therapy, and multidisciplinary care. HER2-directed treatment is most effective when integrated with pathology, oncology, surgery, radiation, and supportive care.

Understanding HER2 biology and testing

Human epidermal growth factor receptor 2, or HER2, is a cell-surface protein involved in growth signaling. Gene amplification or protein overexpression can lead to uncontrolled proliferation in a subset of esophageal and gastroesophageal junction adenocarcinomas. HER2 status may also change between the primary tumor and metastatic sites, making tissue evaluation clinically significant.

Testing usually begins with immunohistochemistry to measure HER2 protein expression. Equivocal results may require in situ hybridization, such as fluorescence in situ hybridization, to assess gene amplification. Because esophageal tumors can display uneven HER2 expression, adequate biopsy sampling and review by an experienced gastrointestinal pathologist are essential.

Where trastuzumab fits

Trastuzumab is a monoclonal antibody that binds HER2 and blocks key signaling pathways. Its established role in advanced HER2-positive gastric and gastroesophageal junction adenocarcinoma, combined with platinum and fluoropyrimidine chemotherapy, has influenced treatment strategies for related esophageal tumors. The strength of evidence is greatest in the gastric and junctional populations represented in clinical trials.

For a patient with esophageal adenocarcinoma, treatment selection should distinguish between disease arising in the esophagus and tumors classified as gastroesophageal junction cancer. The oncologist may consider trial data, local approval status, tumor characteristics, and the intended treatment setting before recommending trastuzumab-based therapy.

Immunotherapy has also become relevant. In selected advanced HER2-positive esophagogastric cancers, combining trastuzumab and chemotherapy with a PD-1 inhibitor may be considered when supported by regulatory guidance and biomarkers such as PD-L1 combined positive score. This approach requires individualized assessment because benefit varies across disease subgroups.

Options after initial HER2 treatment

Disease progression after trastuzumab does not necessarily mean that all HER2-directed strategies are ineffective. Trastuzumab deruxtecan is an antibody-drug conjugate that delivers a topoisomerase I inhibitor directly to HER2-expressing cells. It has demonstrated activity in previously treated HER2-positive gastric and gastroesophageal junction cancers, although its use in esophageal adenocarcinoma depends on the clinical evidence and approval framework applicable to the patient.

Other HER2-targeted agents, including pertuzumab, tucatinib, and oral tyrosine kinase inhibitors, have been evaluated in esophagogastric cancers with mixed results. Their role may be limited to specific clinical trials or carefully selected circumstances. Clinical trial enrollment remains especially valuable for patients with refractory disease or uncommon molecular profiles.

Managing treatment safety

Trastuzumab can cause infusion reactions and has a recognized risk of left ventricular dysfunction. Baseline cardiac assessment and periodic monitoring may be appropriate, particularly for patients with previous heart disease or exposure to cardiotoxic chemotherapy. Symptoms such as breathlessness, edema, or unexplained fatigue should be assessed promptly.

Trastuzumab deruxtecan requires special vigilance for interstitial lung disease and pneumonitis. New cough, shortness of breath, fever, or reduced exercise tolerance should not be ignored. Treatment may need to be interrupted or discontinued if significant pulmonary toxicity develops. Nausea, myelosuppression, and fatigue are also relevant when planning supportive care.

Integrating biomarkers into decisions

HER2 status is only one component of treatment planning. PD-L1 expression, mismatch repair or microsatellite instability status, tumor mutation characteristics, nutritional condition, organ function, and previous therapies can all influence the sequence of care. A single biopsy may not capture the full molecular diversity of advanced disease.

Repeat biopsy or circulating tumor DNA analysis may be useful in selected situations, although liquid biopsy cannot replace tissue confirmation in every setting. Multidisciplinary tumor boards can help reconcile pathology findings with imaging, symptoms, surgical feasibility, and patient preferences.

Practical priorities for clinical teams

• Confirm HER2 status with validated immunohistochemistry and, when indicated, in situ hybridization.
• Clarify whether the tumor is esophageal, gastroesophageal junction, or gastric in origin before applying trial evidence.
• Review PD-L1, mismatch repair, and other relevant biomarkers alongside HER2 results.
• Assess cardiac function before and during HER2-directed treatment.
• Educate patients about respiratory symptoms associated with antibody-drug conjugates.
• Reassess treatment goals and clinical trial eligibility when disease progresses.

Advances in targeted therapy are making molecular classification increasingly important in esophageal adenocarcinoma. Clinicians and researchers can use ISDE educational resources, scientific presentations, and international collaboration to follow emerging evidence and refine treatment pathways. Review the available congress materials and current specialist guidance to support informed, multidisciplinary care for patients with HER2-positive disease.