Radical treatment for metastasis of HER2-positive rectal adenocarcinoma to the liver: A case report and literature review.

Human epidermal growth factor receptor 2 (HER2) positivity, including gene amplification and mutation, is uncommon in colorectal cancer (CRC), with an incidence of only ~5%. Targeted HER2 therapy has been shown to be feasible in patients with HER2-positive CRC after the failure of standard treatments. However, the importance of anti-HER2 therapy in patients with HER2-positive CRC is not yet fully reflected in clinical guidelines. The present report describes the case of a 60-year-old female patient who presented with abdominal pain and bloody stools and was diagnosed with rectal adenocarcinoma and liver metastasis. The next-generation sequencing of biopsy tissue obtained during colonoscopy suggested HER2 mutation/amplification. After two cycles of chemotherapy, the tumor marker levels of the patient continued to increase, indicating poor treatment efficacy. The patient subsequently received six cycles of chemotherapy combined with anti-HER2 therapy, leading to a reduction in tumor marker levels and gradual shrinkage of the lesions. After this, the colorectal and liver lesions were surgically removed. There is currently no definitive treatment for HER2-positive CRC. However, the present case highlights a favorable response to anti-HER2 therapy in a patient with HER2-positive metastatic CRC, suggesting that this treatment approach may be beneficial for HER2-positive CRC and warrants further investigation.