Successful treatment with trastuzumab plus chemotherapy as the first‑line regimen in advanced small bowel adenocarcinoma harboring HER2 amplification: A report of two cases.

Therapeutic options are limited for individuals with unresectable or metastatic small bowel adenocarcinoma (SBA), necessitating palliative chemotherapy. Human epidermal growth factor receptor 2 (HER2) gene amplification or protein overexpression in SBA is exceedingly rare. HER2 amplification mutations/overexpression serves as a potential target for treatment in various malignancies. However, research on targeted therapies for SBA with mutation is lacking. In this context, the present study reports two cases of advanced SBA with a amplification mutation. Both patients received the anti-HER2 agent trastuzumab in combination with an oxaliplatin-based chemotherapy regimen as a first-line treatment. Following disease progression, trastuzumab was used in conjunction with other palliative chemotherapy regimens. Notably, anti-HER2 treatment resulted in significantly extended overall survival times without the occurrence of serious treatment-related adverse events. The overall survival times of the two patients were 31 and 15 months. Additionally, a review of the existing literature was conducted with regard to the effectiveness of anti-HER2 agents in the treatment of advanced SBA. It can be concluded that it is imperative to ascertain the HER2 status prior to the initiation of palliative treatment.